Preparation and performance evaluation of polymer intercalated montmorillonite composite high temperature scale inhibitor

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Orthogonal optimization established ideal synthesis parameters, which including a reaction temperature of 75 ℃, an initiator dosage of 0.6%, a solution pH of 7, a reaction time of 12 h, and a monomer ratio of m (AMPS): m (AA): m (DMDAAC): m (MMT) = 48:25:23:4. Moreover, the molecular structure and thermal stability of CT-5 were characterized by FTIR, XRD, and TG-DTG, as a result, the polymer intercalated MMT was successful, and CT-5 had a composite intercalation structure of organic polymer/inorganic montmorillonite, with a thermal decomposition temperature of 235.24 ℃. Salt tolerance evaluation demonstrated robust performance under saline conditions. The scale inhibition mechanism of CT-5 was explored through scale inhibition rate testing, interlayer spacing testing at different temperatures, characterization of CaCO 3 scale crystal structure and morphology, and chemical binding energy testing of CaCO 3 scale crystals. The CT-5 can release effective chelating groups in the intercalation layer at high temperature, which inhibits the formation of CaCO 3 scale by chelating Ca 2+ to form chelates, and also forms an adsorption layer on the surface of CaCO 3 scale crystals to interfere with the normal growth of CaCO 3 scale crystals and change the lattice structure of CaCO 3 scale crystals, thereby achieving the scale inhibition effect. Physical sciences/Energy science and technology/Fossil fuels Physical sciences/Chemistry/Energy Physical sciences/Engineering/Chemical engineering High temperature scale inhibitor Organic-inorganic composite Water-gas reservoirs Interlayer space CaCO3 scale crystals Scale inhibition mechanism Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Longwangmiao Gas Reservoir in Sichuan Basin, China is a typical high temperature and high-pressure gas reservoir with ultra-large low porosity and high pressure with water. The buried depth is 4600 ~ 4900 m, the temperature in the middle of the gas reservoir is 145 ℃, and the formation pressure is as high as 74 ~ 78 MPa [ 1 ] . Progressive exploitation of the Longwangmiao gas reservoir has exacerbated aquifer encroachment, wherein high-TDS formation water under high-pressure, high-temperature (HPHT) downhole conditions triggers calcium carbonate scaling, as a result, an increase in the friction coefficient of the wellbore and the throttle phenomenon in the wellbore were formed, which will seriously affect the normal production of the producing wells and seriously restrict the upper production of the gas field [ 2 ] . However, the current studies comprehensively address scale formation mechanisms in gas reservoirs, and the critical knowledge gaps persist regarding design and preparation, structure-activity relationship, and mechanism of action of scale inhibitors in specific environments of gas reservoirs. Currently, the scale inhibitor solution with certain concentration was applied to solve the problem of scaling inside the wellbore depends on the combination of functional groups in the scale inhibitor, and the main mechanism is that the combination of functional groups in the scale inhibitor (such as phosphonic acid, carboxylic acid, sulfonic acid, and amide groups) and Ca 2+ to delay the growth of CaCO 3 scale crystals and inhibit the formation of CaCO 3 scale. Presently, the scale inhibitors, such as natural polymers, phosphates, copolymers and environmental-friendly types, are widely used [ 3 – 4 ] . Undeniably, the formation of CaCO 3 scale has been effectively reduced to some extent by these traditional types of scale inhibitors, but, there are also some drawbacks that limit its further promotion and application, such as the easy decomposition of natural polymer scale inhibitors at high temperatures [ 5 ] . Besides, the principal limitation of phosphate-based scale inhibitors resides in their propensity to undergo pronounced thermal hydrolysis under high temperature, which subsequently induces aquatic eutrophication through phosphate release [ 7 ] . Moreover, the copolymer scale inhibitors are further challenged by suboptimal thermal tolerance and non-negligible eco-toxicity, particularly under prolonged operational conditions. Furthermore, the environment-friendly scale inhibitors demonstrate favorable environmental compatibility, but they exhibit compromised scale inhibition efficacy under elevated-temperature conditions [ 8 ] . Recently, some organic scale inhibitors were developed by adding functional groups, such as sulfonic acid groups, which with excellent performance under high temperature. However, the organic scale inhibitors are main used in cooling water circulation system, and the application temperature is basically not more than 100 ℃ [ 9 – 10 ] . Scale inhibition performance under elevated thermal conditions is inherently compromised by structural heterogeneity within organic polymer matrices, resulting in suboptimal or negligible scaling mitigation efficacy [ 11 ] . Montmorillonite (MMT) functions as an active polymerization filler primarily due to its expandable interlayer spaces, high-aspect-ratio nanolayers, and intrinsic cation-exchange capability, synergistically enhance polymer nucleation and matrix integration. Secondly, which distinct from conventional fillers, such as silica or carbon black, MMT's structural anisotropy facilitates monomer intercalation within its aluminosilicate galleries, enabling in situ exfoliation during polymerization to achieve homogeneous dispersion. Moreover, its superior interfacial interactions with initiators or monomers, coupled with exceptional thermal stability ensure structural integrity under high-temperature polymerization conditions [ 12 ] . Regarding the problem of poor temperature resistance of the scale inhibitor mentioned above, based on the characteristics of MMT, during this study, a polymerizable quaternary ammonium salt was used to modify montmorillonite, which could use as an active polymerizable filler [ 12 ] . Then, the intercalated MMT served as reactive filler for synthesizing high-temperature scale inhibitor CT-5 via in-situ polymerization of AMPS, AA, and DMDAAC monomers. Structural characterization (XRD, FTIR, TGA) and mechanistic analysis revealed enhanced thermal stability. This organic-inorganic composite broadens the chemical diversity of scaling inhibitors, establishing a design framework for thermally adaptive materials. 2. Materials and methods 2.1. Materials 2-acrylamido-2-methylpropanesulfonic acid (AMPS), diallyldimethylammonium chloride (DMDAAC), acrylic acid (AA), sodium bisulfite (NaHSO 3 ), potassium persulfate (K 2 S 2 O 8 ) is all analytical grade, which purchased from Kelong Chemical plant (Chengdu, China). Montmorillonite (MMT) is an industrial product, which purchased from Xinjiang Zhongfei Xiazi Street Bentonite Co., Ltd. 2.2. Synthesis of CT-5 2.2.1 Selection of Co-monomers Due to the presence of long-chain side groups and sulfonic acid groups with good temperature and salt resistance in the molecular structure of AMPS, it has a significant steric hindrance effect and strong coordination effect, which can effectively improve the temperature resistance of polymers. Therefore, AMPS is chosen as the main monomer [ 13 ] . The carboxylic acid groups in the molecular structure of AA have good coordination and strong electronegativity, and can form complexes with Ca 2+ in the liquid phase, which can not only improve the hydrophilicity and coordination of polymer, but also enhance the scale inhibition performance [ 14 ] . DMDAAC is a cationic monomer, which can enlarge the layers spacing of montmorillonite, facilitating the insertion and release of polymers [ 15 ] . As discussed in above, the MMT has the characteristics of layers structure, hydrothermal expansion and high thermal stability [ 12 ] , which can not only improve high thermal stability of polymers, but also enhance the scale inhibition effect at high temperature through the polymer intercalation bound release function. The mechanism of polymer intercalated organic montmorillonite is as follows: RNRʹ 3 X + M-Mont →RNRʹ 3 -Mont + MX (R—Organic group; Rʹ—H; X—Cl − , Br − , I − ; M—Na + , Ca 2+ , Mg 2+ ) The polymerization reaction of AA/AMPS/DMDAAC is shown in Fig. 1 , and the preparation process of polymer/montmorillonite is shown in Fig. 2 . 2.2.2 The synthesis process of CT-5 a Pretreatment of MMT Add a certain amount of DMDAAC to a suspension of montmorillonite with a solid content of 5%, and after ultrasonic dispersion, centrifuging, washing, and drying, the pre-treated modified MMT is obtained. b The preparation process of CT-5 Mix a certain amount of pre-treated modified MMT with deionized water and place it into a flask. Then weigh 12.5 g of AMPS, 8.3 g of AA, and 4.2 g of DMDAAC respectively, dissolve the weighed mixed monomers in deionized water (monomer mass fraction is 25%), adjust its pH value to 7, and then pour the mixed solution into the flask. Then, nitrogen was continuously injected for 10 min, stirred at 40 ℃ for 20 min, and then heated to 70 ℃, and 0.6% initiator solution was added. Then, the CT-5 can be obtained after the reaction at this temperature for 5 h and cooling to room temperature. For the subsequent application of scale inhibition and analysis of scale inhibition related mechanisms, the solubility of CT-5 was measured, as a result, the solubility of CT-5 is very good within the temperature range of 70 ~ 130 ℃, reaching 100%. 2.3 Structure characterization and scale inhibition performance evaluation method of CT-5 The product obtained after reaction is firstly added to ethanol in batches, and with leaching, drying, grinding, and then dissolved in distilled water. Moreover, the product is leached by acetone to obtain orange powder, which could be used to structure characterization. 2.3.1 Infrared analysis The obtained orange powder was characterized by infrared spectroscopy using a WQF-520 Fourier transform infrared spectrometer (Nicolette, USA) with a scanning range of 400 ~ 4000 cm − 1 . 2.3.2 Thermogravimetric analysis The thermal stability of the powder was analyzed by using the STA449F3 synchronous comprehensive thermal analyzer (NETZSCH, Germany) at a temperature of 50 ~ 450 ℃ with the heating rate of 5 ℃/min, and nitrogen atmosphere used. 2.3.3 X-ray diffraction analysis The phase composition of the powder was characterized by an X'Pert MPD PRO X-ray diffractometer (Panat, Netherlands) with a tube voltage of 40 kV, a tube current of 40 mA, a scanning rate of 2 °/min, and a scanning range of 1° ~ 10°. 2.3.4 Scale inhibition performance test During this study, the CaCO 3 scale type standard saline water was prepared depending on the method described in SY/T 5673 − 2020 "General Technical Conditions for Oilfield Scale Inhibitors", then, the CaCO 3 scale samples were simulated according to the method described in this standard. Furthermore, the scale inhibition rate of CaCO 3 scale was investigated. 2.3.5 Chelation amount and layer spacing test After the experiment on the scale inhibition rate of CT-5 at different temperatures, the reacted solution was centrifuged at high speed, and the free Ca 2+ content in the supernatant was measured to calculate the chelation amount of Ca 2+ . 2.3.6 Scanning electron microscope The microscopic morphology of CaCO 3 scale crystals with or without CT-5 was analyzed by using a FlexSEM1000 compact intelligent scanning electron microscope. Before running testing, the gold spraying was required to enhance the conductivity of the sample. 2.3.7 X-ray photoelectron spectroscopy The X-ray photoelectron spectroscopy (XPS) is a typical surface analysis method that can qualitatively analyze the elemental composition and chemical state of material surfaces. Moreover, it can quantitatively analyze the elemental content on the surface of materials. Static scale inhibition experiments were conducted, and the adding amount of CT-5 is 0 and 4%. After filtering and separating a small amount of solid in the bottle, it was dried in a vacuum chamber and analyzed for changes in the binding energy of Ca 2p and O 1s orbitals using X-ray photoelectron spectroscopy. 3. Results and discussion 3.1 Optimization of preparation conditions of CT-5 Taking the scale inhibition rate as the main evaluation index, the optimal conditions for the synthesis of CT-5 were optimized, and the orthogonal experiment of copolymerization reaction was designed, as shown in Table 1 . According to the principle of free radical polymerization, the main factors affecting the properties of co-polymer products are monomer mass ratio A [m (AMPS): m (AA): m (DMDAAC): m (MMT)], reaction temperature B (℃), initiator dosage C (%), reaction time D (h), and solution E (pH). Based on this, a five factor four level orthogonal experiment was constructed to analyze the main factors affecting copolymerization and the optimal synthesis conditions. Here, the K1 * , K2 * , K3 * and K4 * is the average scale inhibition at levels 1, 2, 3 and 4, respectively. Besides, the R is the range between different levels under the same factor conditions. Table 1 Orthogonal experimental table of co-polymerization Experiment number Experimental factors scale inhibition ratio (%) A B(℃) C(%) D(h) E(pH) 1 55:30:13:2 60 0.20 6 9 77.6 2 55:30:13:2 65 0.40 8 8 89.3 3 55:30:13:2 70 0.60 10 7 91.8 4 55:30:13:2 75 0.80 12 6 95.2 5 48:25:23:4 60 0.40 8 8 81.2 6 48:25:23:4 65 0.20 10 6 85.7 7 48:25:23:4 70 0.80 12 9 90.5 8 48:25:23:4 75 0.60 6 7 97.6 9 40:30:34:6 60 0.60 10 7 80.5 10 40:30:34:6 65 0.80 12 9 85.1 11 40:30:34:6 70 0.40 6 6 88.2 12 40:30:34:6 75 0.20 8 8 92.1 13 32:15:45:8 60 0.80 12 6 72.3 14 32:15:45:8 65 0.60 6 7 76.7 15 32:15:45:8 70 0.20 8 8 79.2 16 32:15:45:8 75 0.40 10 9 83.1 K1* 88.475 77.9 83.65 85.025 84.075 K2* 88.75 84.2 85.45 85.45 85.45 K3* 86.475 87.425 86.65 85.275 86.65 K4* 77.825 92 85.775 85.775 85.35 R* 10.65 14.1 3 0.75 2.575 Which as shown in Table 1 , the orthogonal analysis revealed reaction temperature as the predominant factor affecting inhibitor performance (highest range value in Table 1 ), followed sequentially by monomer mass ratio, initiator dosage (%), pH and reaction time (h). The optimal synthesis protocol (B4A2C3E3D4) derived from orthogonal mean analysis comprised, namely, the reaction temperature is 75 ℃, the monomer mass ratio is 48:25:23:4, the initiator dosage is0.6%, the pH is 7, and the reaction time is 12 h. CT-5 synthesized under these conditions underwent subsequent analytical characterization. 3.2 Structural characterization of CT-5 3.2.1 Infrared spectrum characterization of CT-5 The infrared spectrum characterization results of CT-5 are shown in Fig. 3 . In Fig. 3 , 3477 cm − 1 is the N-H characteristic peak contained by the amide group in the molecular structure of AMPS, and the stretching vibration absorption peak of -CH 3 is located at about 2936 cm − 1 . The stretching vibration absorption peaks of C = O in AA and AMPS are located at about 1724 and 1655 cm − 1 , respectively. The deformation vibration stretching peak of N-H is located at about 1552 cm − 1 , and the stretching vibration absorption peaks of C-N in AMPS and DMDAAC are located at about 1438 and 1368 cm − 1 . The stretching vibration absorption peaks of SO 3 − are located at about 1230, 1043, and 1175 cm − 1 , respectively. At 630 cm − 1 is the deformation vibration peak of C-N five-membered ring in DMDAAC. However, compared to P (AA/AMPS/DMDAAC), the infrared spectrum of CT-5 shows distinct peaks at 1106 cm − 1 and 463 cm − 1 , with the peak at 1106cm − 1 being the stretching vibration peak of Si-O and the peak at 463cm − 1 being the bending vibration peak of Si-O [ 16 ] . It can be seen from the above analysis that the functional groups of three monomers and MMT appear in the spectrum, which indicates that the polymer and MMT are successfully combined, and the CT-5 is the target product. 3.2.2 XRD Characterization of CT-5 The XRD characterization results of MMT and scale inhibitor CT-5 are shown in Fig. 4 . From Fig. 4 , it can be seen that the layer spacing of MMT is 1.208 nm (2 θ = 7.31). The diffraction peak of CT-5 shifted to the left and the intensity significantly decreased, and the peak shape showed a wide and diffuse raised package shape, with an increased interlayer spacing of 1.522 nm (2 θ = 5.80). According to the literature [ 17 – 18 ] , when the interlayer spacing increases beyond the small angle X-ray diffraction range, only the intercalated portion can be diffracted. Figure 4 shows a decrease in the intensity of the CT-5 diffraction peak, indicating that the polymer has been successfully intercalated between the layers of MMT, forming a composite material with an intercalation structure. 3.2.3 Thermal stability analysis of CT-5 The thermal stability analysis of CT-5 is listed in Fig. 5 . Figure 5 a and Fig. 5 b shows the initial thermal decomposition temperature of P (AMPS/AA/DMDAAC) and CT-5 is about 218.42 and 235.24 ℃. The above phenomenon indicates that the addition of MMT significantly improves the thermal stability of CT-5, making the composite intercalated polymer CT-5 have good temperature resistance and resistance characteristics. On the one hand, it is due to the excellent thermal stability of MMT. On the other hand, due to the intercalation of the polymer between the layers of MMT, the layers not only can effectively shield thermal decomposition effects, but also hinder the movement of small molecules generated by polymer molecules during thermal decomposition. Therefore, CT-5 exhibits good thermal stability. 3.3 Performance evaluation of CT-5 application 3.3.1 Scale inhibition effect of CT-5 at high temperature Excellent scale inhibition performance at high temperature is the main performance indicator of high temperature scale inhibitors, however, polymer scale inhibitors are prone to functional group decomposition, molecular chain breakage, and high-temperature desorption under high temperature conditions, resulting in a significant reduction or even complete loss of scale inhibition effect. In this section, the scale inhibition rates are tested at different temperature points and CT-5 dosage to investigate the scale inhibition performance of CT-5 at high temperatures, and the results are shown in Table 2 . Table 2 The scale inhibition rate at different temperature and different CT-5 dosage Scale inhibitor 70℃ 90℃ 110℃ 130℃ 2% 4% 6% 2% 4% 6% 2% 4% 6% 2% 4% 6% P(AMPS/AA /DMDAAC) 87.4 93.6 91.2 80.3 84.1 82.5 70.7 77.6 64.0 43.5 59.3 52.4 CT-5 85.1 89.7 90.5 81.7 85.3 83.2 76.1 82.3 80.6 68.9 73.4 70.5 Which as shown in Table 2 , on the one hand, the scale inhibition rates of P(AMPS/AA/DMDAAC) and CT-5 show a trend of first increasing and then decreasing with the increase of dosage, the scale inhibition rate of P(AMPS/AA/DMDAAC) and CT-5 with 4% adding amount is 93.6 and 89.7% at the temperature of 70 ℃, of course, which shows similar patterns at other temperatures ( the adding amount will be used for subsequent evaluation and mechanism research experiments). Moreover, it was also demonstrated that the scale inhibition rate of CT-5 is slightly lower than that of P(AMPS/AA/DMDAAC) at low temperature, such as 70 ℃, which may due to the layered structure of MMT in CT-5 affecting the chelating ability of anionic groups to Ca 2+ . However, it was also demonstrated that the scale inhibition rate of CT-5 is higher than that of P(AMPS/AA/DMDAAC) at high temperature, the scale inhibition rate of CT-5 with 4% adding amount is higher than that of P(AMPS/AA/DMDAAC) by 1.2, 4.7 and 14.1% at the temperature of 90, 110 and 130 ℃, respectively. Besides, the scale inhibition rate of P(AMPS/AA/DMDAAC) decreases from 93.6–59.3%, a decrease of 34.3% was observed, while the scale inhibition rate of CT-5 decreases from 89.7–73.4%, a decrease of only 16.3%. Based on the data from the above two aspects, CT-5 has the good high-temperature resistance performance. Additionally, which as discussed above, the scale inhibition rates of CT-5 with 4% adding amount is larger than that 2 and 6% at the temperature of 110 and 130 ℃, the main reason is that scale inhibitors form soluble complexes by combining functional groups (such as sulfonic acid and carboxylic acid groups) with scaling ions (such as Ca ² ⁺) to inhibit crystal growth, and when the adding amount of CT-5 is 4%, the molar ratio of CT-5 molecules to Ca 2+ approaches stoichiometric equilibrium, achieving maximum complexation efficiency. However, exceeding the optimal concentration (6%), excessive CT-5 molecules may compete for binding sites or form molecular aggregates, thereby reducing effective activity. Simultaneously, the reason for scale inhibition rates of CT-5 decreased when the temperature beyond 130 ℃ is that high temperature causes thermal cracking of active functional groups (such as sulfonic acid groups and carboxylic acid groups) and molecular main chains in CT-5 molecules, on the other hand, the high temperatures may also intensify the thermal motion of polymer chains, leading to disordered molecular conformation and masking of active sites of CT-5, resulting in a decrease in scale inhibition effectiveness. 3.3.2 Evaluation of salt resistance of CT-5 The high mineralization environment in deep and ultra deep wells can affect the extension of polymer molecular chains, causing a sharp change in the scale inhibition effect of scale inhibitors. Therefore, scale inhibitors need to have excellent salt resistance performance. In this section, the scale inhibition rate of CT-5 was measured at 130 ℃ with different NaCl contents to investigate the salt resistance performance of CT-5, and the results are shown in Fig. 6 . The Fig. 6 shows that the scale inhibition rate of CT-5 presents a trend of first increasing and then stabilizing with the increase of NaCl content, and the scale inhibition rate of CT-5 with 4% adding amount is 73.4 and 76.9% by the salt content of 0 and 8%, and the change rate is 4.76%. Besides, when the NaCl content is less than 4%, the scale inhibition rate of CT-5 increases significantly with the increase of NaCl content, but when the NaCl content exceeds 4%, the scale inhibition rate of CT-5 increases slowly and tends to be stable with the increase of NaCl content, which is consistent with relevant literature [ 19 ] . The reason for the above phenomenon may be related to the molecular structure of the scale inhibitor. Due to the presence of both cationic and anionic groups in polymer molecules, there are two types of binding interactions within and between molecules. The shielding effect of NaCl hinders the binding interactions within and between the molecules, making the molecular chains of the polymer to unfold, enhancing the adsorption and chelation effects of molecular chains, disrupting the normal growth of scale crystals and increasing the scale inhibition rate [ 21 – 22 ] . 3.4 Study on scale inhibition mechanism of CT-5 at high temperature Presently, it is believed that the scale inhibition mechanism of scale inhibitors as follows [ 22 – 23 ] . At first, the anionic groups within scale inhibitor molecules form soluble chelate complexes with scale-forming cations, such as Ca²⁺ in aqueous solutions, thereby inhibiting crystalline growth and exerting their scale inhibiting function. Moreover, through adsorption onto scale microcrystal surfaces, these anionic groups establish electrical double layers that generate surface electrostatic repulsion, which effectively preventing microcrystal aggregation into macroscopic deposits. Furthermore, scale inhibitors disrupt the regular lattice arrangement during crystal growth, inducing lattice strain that weakens structural integrity and promotes crystalline fragmentation, ultimately achieving scale inhibition through mechanical destabilization. In this part, the release mechanism of CT-5 at high temperature and its effect on the crystal structure of CaCO 3 scale were studied by measurement of chelation amount of Ca 2+ at different temperatures, XRD, SEM and XPS tests, and then the scale inhibition mechanism of CT-5 was further studied. 3.4.1 Release mechanism of CT-5 at high temperature To investigate the scale inhibition mechanism of CT-5, the changes in layer spacing and Ca 2+ chelation amount of CT-5 at different temperatures were measured, and then compared with the chelation amount of Ca 2+ by P(AA/AMPS/DMDAAC), as shown in Fig. 7 . Which as shown in Fig. 7 , the results show that the interlayer spaces of CT-5 gradually increase with the increase of temperature, which is caused by thermal expansion of the layers of MMT in the CT-5 at high temperatures, the interlayer spaces increased by 63.49% when the temperature rises from 80 to 130 ℃. Then, it was also found that the chelation amount of Ca 2+ by P(AMPS/AA/DMDAAC) and CT-5 decreases with the increase of temperature, the reason is that the chelating groups of polymer molecules have a dynamic equilibrium process of adsorption and desorption. Specifically, at high temperature, it is manifested as a decrease in the chelation amount of Ca 2+ when the desorption effect is greater than the adsorption effect. But the decreasing trend of the chelating amount of Ca 2+ by CT-5 with increasing temperature is significantly slower than that of P(AMPS/AA/DMDAAC), which indicating that CT-5 is less sensitive to temperature. The reason is that the layer spacing of MMT expands by thermal expansion, the thermal motion of polymer molecules intensifies, and the polymer molecules originally curled up between the MMT layers is gradually released with the increase of the layer spacing, causing an increase of effective adsorption groups. Therefore, the CT-5 has a higher chelation amount to Ca 2+ , as a result, the trend of decreasing the chelation amount of Ca 2+ with increasing temperature is slower. 3.4.2 Effect of CT-5 on the crystal structure of CaCO 3 The effect of CT-5 on the crystal structure of CaCO 3 scale was analyzed by XRD, and compared with the original CaCO 3 scale. Figure 8 shows the XRD analysis results of CaCO 3 scale crystals with and without CT-5. According to the XRD analysis of CaCO 3 scale crystals in the solution without CT-5 shown in Fig. 8 , only the characteristic diffraction peaks of CaCO 3 (calcite) are observed at 23.2°, 29.4°, 31.5°, 36.3°, 38.5°, 43.0°, 47.2° and 47.9° [ 24 – 25 ] . At the same time, the diffraction peak at 29.4° is sharper and higher than others, indicating that the CaCO 3 scale crystals mainly grew along this crystal plane. The XRD analysis of CaCO 3 scale crystals in solution with CT-5 in Fig. 8 shows that the characteristic diffraction peak of CaCO 3 (calcite) only appears at 23.2°, the characteristic diffraction peak of CaCO 3 (aracharite) appears at 36.0 and 47.6° [ 26 ] . Unlike the XRD results of CaCO 3 scale crystals in solution without CT-5, the XRD analysis spectrum of CaCO 3 scale crystals in solution with CT-5 shows characteristic diffraction peaks of CaCO 3 (aragonite) with the character of loose structure and easy physical damage at 21.0°, 25.0°, 27.1°, 32.8°, 39.5° and 43.2° [ 27 – 28 ] . The characteristic peaks belonging to both CaCO 3 (calcite) and CaCO 3 (aragonite) decrease significantly, indicating that the main component in the crystal is CaCO 3 (vaterite). On the one hand, the anion group in CT-5 can not only bind with Ca 2+ , hindering the binding of Ca 2+ with other anions such as CO 3 2− . On the other hand, the CT-5 can also change the crystal structure of CaCO 3 scale crystals and affect the growth of crystals, thereby improving the scale inhibition effect [ 29 – 30 ] . 3.4.3 Analysis of the effect of CT-5 on the crystal morphology of CaCO 3 The CaCO 3 crystals primarily as calcite (rhombohedral), aragonite (acicular), and vaterite (spheroidal aggregates with polydispersity) [ 31 – 33 ] . SEM analysis revealed CT-5-induced morphological modification of CaCO 3 deposits, elucidating its scale inhibition mechanism. Figure 9 contrasts the crystallographic features of CaCO 3 scale crystals with and without CT-5. The magnification used in the SEM of CaCO 3 scale crystals without CT-5 is 2000, 4000 and 10000, the magnification used in the SEM of CaCO 3 scale crystals with 2.0% CT-5 is 1000, 4000 and 10000, the magnification used in the SEM of CaCO 3 scale crystals with 4.0% CT-5 is 1000, 2000 and 4000, which has been also added in the revised manuscript. Figure 9 a shows the CaCO 3 scale crystal without adding CT-5 is regular cubic shape with dense structure, indicating that the type of CaCO 3 crystals is calcite. However, Fig. 9 b and Fig. 9 c show that the morphology of CaCO 3 scale crystals changes significantly after the addition of CT-5. Figure 9 b shows that when the content of CT-5 is 2%, most CaCO 3 crystals appear as irregular angular shapes, only a small number of CaCO 3 crystals appear as rod-shaped, and there are almost no regular cubic CaCO 3 crystals. As the content of CT-5 increases, the morphology of CaCO 3 scale crystals continues to be changed. Figure 9 c shows that when the content of CT-5 increases to 4%, the size of CaCO 3 scale crystals varies and the crystals are irregular spherical, indicating that the type of CaCO 3 crystals are vaterite. In addition, it can be clearly seen from Fig. 9 c 2 that there are obvious cracks on the surface of CaCO 3 crystals, indicating that the structure of CaCO 3 crystal is relatively loose, which is consistent with the description of the unstable thermodynamic state and structure of vaterite in the literature [ 28 ] . The above characterization results indicate that the CT-5 achieves scale inhibition by changing the crystal structure of CaCO 3 , which may due to the anionic groups of CT-5 adsorbing on the surface of CaCO 3 scale crystals by chelation of Ca 2+ and electrostatic interactions, occupying the growth active sites of CaCO 3 scale crystals [ 34 – 35 ] , causing lattice distortion of CaCO 3 scale crystal and achieving the scale inhibition effect. 3.4.4 Chemical binding energy analysis of CT-5 on CaCO 3 crystals XPS revealed CT-5-induced chemical binding energy modulation in CaCO 3 scale crystals, elucidating its inhibition mechanism [ 36 ] . Figure 10 compares the XPS spectra of CaCO 3 deposits in scale-inhibited and control systems, namely, the XPS results of CaCO 3 scale crystals in solution with and without scale inhibitor CT-5. As shown in Fig. 10 (a), only energy peaks of elements Ca, C and O appear in the XPS spectrum of CaCO 3 scale crystals in solution without CT-5, however, in the XPS spectrum of CaCO 3 scale crystals in the solution with CT-5, in addition to the energy peaks of elements Ca, C, and O, there are also energy peaks of elements N (391.5 eV) and S (169.3 eV), which may be resulting from the raw materials AMPS and DMDAAC. The high-resolution spectrum of Ca 2P in Fig. 10 (b) shows that energy peaks belonging to Ca 2p1/2 and Ca 2p3/2 of CaCO 3 scale crystals in solution without CT-5 appear at 350.6 and 347.1 eV, respectively [ 37 ] . The energy peak positions ascribed to Ca 2p1/2 and Ca 2p3/2 in CaCO 3 scale crystals in solution with CT-5 are 350.1 and 346.7 eV, respectively. Compared with high-resolution spectrum of Ca 2P in CaCO 3 scale crystals in solution without CT-5, the binding energy of Ca 2P in CaCO 3 scale crystals in solution with CT-5 has shifted to a lower binding energy direction by 0.5 eV. This indicates that the CT-5 can change the chemical environment of element Ca, because the anionic groups in CT-5 will bind with Ca 2+ , transfer and contribute some electrons to Ca 2+ , thereby increasing the electron density of the outer layer of Ca, and causing a decrease in the binding energy of Ca [ 16 , 38 – 39 ] . The above experimental results show that the anionic groups in CT-5 are bound to Ca 2+ , thus hindering the scale formation of Ca 2+ and other anions, and inhibiting the normal growth of CaCO 3 scale crystals. 3.4.5 Scale inhibition mechanism of CT-5 at high temperature According to the molecular chain of polymer P(AA/AMPS/DMDAAC) and the structure of MMT in Fig. 1 and Fig. 2 , it can be seen that CT-5 has good high temperature resistance due to the high temperature resistance of MMT layer, as well as the existence of five membered ring structures of polymer molecular chain and the group of sulfonic acid root in molecular side chain. By studying the effect of temperature on the layer spacing of CT-5 and the chelation amount of Ca 2+ , it can be seen that the higher the temperature and the larger the layer spacing, the more scale inhibiting groups in free fluid, indicating that CT-5 can release different amounts of scale inhibiting groups at different temperatures. By utilizing the characteristics of the MMT layer and thermal expansion, CT-5 with good scale inhibition performance at high temperatures. By analyzing the effect of CT-5 on the structure of CaCO 3 crystal scale through XRD, SEM and XPS, combined with the molecular structure of CT-5, it can be inferred that the sulfonic acid and carboxylic acid groups with strong coordination in the polymer will form chelates with free Ca 2+ in solution. On the one hand, the concentration of Ca 2+ in free liquid is reduced, and the probability of Ca 2+ binding with CO 3 2− and other scale ions is reduced. On the other hand, the anionic groups of CT-5 adsorbing on the surface of CaCO 3 scale crystals, hindering the normal growth of CaCO 3 scale crystals, changing the lattice structure of CaCO 3 scale crystals, and achieving scale inhibition effect [ 27 , 40 – 41 ] . Besides, the scale inhibition mechanism of CT-5 is shown in Fig. 11 . 4. Conclusion During this study, the organic-inorganic composite scale inhibitor CT-5 was successfully synthesized via solution polymerization-mediated in situ intercalation using AA, AMPS and DMDAAC as monomers, with MMT as reactive filler. The optimized preparation process parameters include a reaction temperature of 75 ℃, an initiator dosage of 0.6%, a solution pH of 7, a reaction time of 12 h, and a monomer ratio of m (AMPS): m (AA): m (DMDAAC): m (MMT) = 48:25:23:4. The results of FTIR, XRD, and TG-DTG shows that the CT-5 intercalated MMT was successful, which shows a composite intercalation structure of organic polymer/inorganic montmorillonite, and the initial thermal decomposition temperature CT-5 was increased to 235.24 ℃. Performance evaluation of CT-5 application shows that CT-5 has the good high-temperature resistance performance, a decrease of only 16.3% was observed with the temperature increased from 70 to 130 ℃, meanwhile, the scale inhibition rate of CT-5 presents a trend of first increasing and then stabilizing with the increase of NaCl content (0 ~ 8%). Furthermore, the results of release mechanism of CT-5 at high temperature, effect of CT-5 on the crystal structure and morphology of CaCO 3 show that the interlayer space of MMT in CT-5 molecules expands at higher temperatures (90 ~ 130 ℃), and the polymer molecules in the intercalation are released, thus increasing the free adsorption groups, reducing the content of Ca 2+ in the free liquid by forming a complex with Ca 2+ , and inhibiting the normal growth of CaCO 3 crystals to achieve scale inhibition effect. On the other hand, the anionic groups of CT-5 adsorbing on the surface of CaCO 3 scale crystals, hindering the normal growth of CaCO 3 scale crystals, changing the lattice structure of CaCO 3 scale crystals, and achieving scale inhibition effect. Declarations Data Availability/ Availability of Data and Materials The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request. CRediT authorship contribution statement Bojian Zhang: Data curation, Formal analysis, Writing - original draft. Youquan Liu: Supervision, Writing - review & editing. Ying Xiong: Supervision, Writing - review & editing. Cheng Fu: Supervision, Validation, Investigation. Xianbing Wang: Data curation. Declaration of Competing Interest The authors declare no competing financial interest. Funding The research is financially supported by Sichuan Province Science and Technology Plan Project (No. 2023YFG0092). References Fang, F. et al. 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Synthesis, scale and corrosion inhibition evaluation and mechanism of 2-aminobenzimidazole modified polyaspartic acid. J. Environ. Chem. Eng. 12 , 112950 (2024). Horner, O. et al. Antiscalant properties of Herniaria glabra aqueous solution. Desalination 409 , 157–162 (2017). Hu, Y., Chen, C. & Liu, S. Evaluation of microbial agents as corrosion and scale inhibitor for industrial cooling water applications. Water Sci. Technol. 85 , 1904–1919 (2022). Sayed, A., Ashmawy, A., Elgammal, W., Hassan, S. & Deyab, M. Synthesis, description, and application of novel corrosion inhibitors for CS AISI1095 in 1.0 M HCl based on benzoquinoline derivatives. Sci. Rep-UK . 13 , 13761 (2023). Gao, R. et al. ZIF-8@s-EPS as a novel hydrophilic multifunctional biomaterial for efficient scale inhibition, antibacterial and antifouling in water treatment. Sci. Total Environ. 773 , 145706 (2021). Bai, H. et al. Effect of interlayer cations on exfoliating 2D montmorillonite nanosheets with high aspect ratio: From experiment to molecular calculation. Ceram. Int. 45 , 17054–17063 (2019). Guo, X. et al. The synthesis of polyaspartic acid derivative PASP-Im and investigation of its scale inhibition performance and mechanism in industrial circulating water. RSC Adv. 10 , 33595–33601 (2020). Li, S. et al. Bacillus cereus s-EPS as a dual bio-functional corrosion and scale inhibitor in artificial seawater. Water Res. 166 , 115094 (2019). Du, Q., Wang, Y., Li, A. & Yang, H. Scale-inhibition and flocculation dual-functionality of poly(acrylic acid) grafted starch. J. Environ. Manage. 210 , 273–279 (2018). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 07 May, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Accepted 23 Apr, 2025 Reviews received at journal 23 Apr, 2025 Reviews received at journal 19 Apr, 2025 Reviewers agreed at journal 10 Apr, 2025 Reviewers agreed at journal 10 Apr, 2025 Reviews received at journal 10 Apr, 2025 Reviewers agreed at journal 10 Apr, 2025 Reviewers agreed at journal 10 Apr, 2025 Reviewers invited by journal 09 Apr, 2025 Submission checks completed at journal 08 Apr, 2025 First submitted to journal 08 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5131887","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":440746500,"identity":"e47d5288-3a88-4852-85bb-a6043110a9ea","order_by":0,"name":"Zhang 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Department","correspondingAuthor":false,"prefix":"","firstName":"Xianbing","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2024-09-22 09:59:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5131887/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5131887/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-99968-9","type":"published","date":"2025-05-07T15:57:17+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":80337192,"identity":"d34a631c-7949-43e8-b420-d2a3b1b33808","added_by":"auto","created_at":"2025-04-10 16:44:26","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":27674,"visible":true,"origin":"","legend":"\u003cp\u003eCopolymerization equations of AA/AMPS/DMDAAC\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/d1be7631e1b4ebeee495c3c6.jpg"},{"id":80336677,"identity":"0d92e2af-5216-4ad1-a692-66ecac5482f1","added_by":"auto","created_at":"2025-04-10 16:36:26","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":133698,"visible":true,"origin":"","legend":"\u003cp\u003eThe process of P(AA/AMPS/DMDAAC) intercalated MMT\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/d9da383cdafcae6d3be6c76d.jpg"},{"id":80336676,"identity":"461bddc0-f0bd-4fff-b787-f84d418eccb7","added_by":"auto","created_at":"2025-04-10 16:36:26","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":51047,"visible":true,"origin":"","legend":"\u003cp\u003eInfrared Spectra of P(AA/AMPS/DMDAAC) and CT-5\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/118219e4dbcbe798a588ba07.jpg"},{"id":80336680,"identity":"9066e570-8146-4c27-9b78-087384bb6c34","added_by":"auto","created_at":"2025-04-10 16:36:26","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":263161,"visible":true,"origin":"","legend":"\u003cp\u003eXRD spectra of montmorillonite and CT-5\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/864a996ec9a8ef983f151f58.jpg"},{"id":80338249,"identity":"7957f8da-a138-43a4-9cd0-e668395d8779","added_by":"auto","created_at":"2025-04-10 17:00:26","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":213184,"visible":true,"origin":"","legend":"\u003cp\u003eThe TG and DTG distribution curves of P (AA/AMPS/DMDAAC) (\u003cem\u003ea\u003c/em\u003e) and CT-5 (\u003cem\u003eb\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/32d516a1d415ca3e0203f980.jpg"},{"id":80337193,"identity":"ebad5663-da1b-4ed0-97eb-d32bd8ab3cbd","added_by":"auto","created_at":"2025-04-10 16:44:26","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":28647,"visible":true,"origin":"","legend":"\u003cp\u003eChanges on scale inhibition rate of salt resistance of CT-5 with salt content\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/6eb3f6e2f071d7a724cf9555.jpg"},{"id":80338250,"identity":"ccaa52e5-dba7-4edb-8fc9-617354957e7e","added_by":"auto","created_at":"2025-04-10 17:00:26","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":88481,"visible":true,"origin":"","legend":"\u003cp\u003eTest results of layer spacing and Ca\u003csup\u003e2+\u003c/sup\u003e chelation amount of CT-5 at different temperatures\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/eba9df1e5bcadda64ce08b17.jpg"},{"id":80337673,"identity":"141a59d1-0f53-406d-b5a6-16a53a49b89a","added_by":"auto","created_at":"2025-04-10 16:52:26","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":84322,"visible":true,"origin":"","legend":"\u003cp\u003eXRD analysis results of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with and without CT-5 in solution\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/3921af7f2d6c57cf8502723b.jpg"},{"id":80337201,"identity":"92f873be-3fd1-4fd1-b026-c33d71779ef0","added_by":"auto","created_at":"2025-04-10 16:44:26","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":1491019,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of scale inhibitor CT-5 on the morphology of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals. (a) CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals without CT-5, (b) CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with 2% CT-5, (c) CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with 4% CT-5\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/aceb78d41a56dadfab52c848.jpg"},{"id":80337199,"identity":"2c6ee203-f1f9-48f0-baec-c971b728b0ee","added_by":"auto","created_at":"2025-04-10 16:44:26","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":257017,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectrogram of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with or without CT-5. (a) XPS spectra of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with and without CT-5; (b) High-resolution XPS spectrum of the Ca 2p peak\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/7d140fbc343c169be1ddc66f.jpg"},{"id":80337677,"identity":"687e397d-f4c1-474a-9477-09d42cac55be","added_by":"auto","created_at":"2025-04-10 16:52:26","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":185094,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the scale inhibition mechanism of CT-5\u003c/p\u003e","description":"","filename":"Picture11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/3faf1056a0106b81c50e84af.jpg"},{"id":82537622,"identity":"a4554586-89bc-48ab-92ee-6c35f53adb1b","added_by":"auto","created_at":"2025-05-12 16:09:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4264495,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5131887/v1/61b1c3cc-4efe-406e-b27d-f67cac095e4d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Preparation and performance evaluation of polymer intercalated montmorillonite composite high temperature scale inhibitor","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eLongwangmiao Gas Reservoir in Sichuan Basin, China is a typical high temperature and high-pressure gas reservoir with ultra-large low porosity and high pressure with water. The buried depth is 4600\u0026thinsp;~\u0026thinsp;4900 m, the temperature in the middle of the gas reservoir is 145 ℃, and the formation pressure is as high as 74\u0026thinsp;~\u0026thinsp;78 MPa\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Progressive exploitation of the Longwangmiao gas reservoir has exacerbated aquifer encroachment, wherein high-TDS formation water under high-pressure, high-temperature (HPHT) downhole conditions triggers calcium carbonate scaling, as a result, an increase in the friction coefficient of the wellbore and the throttle phenomenon in the wellbore were formed, which will seriously affect the normal production of the producing wells and seriously restrict the upper production of the gas field\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. However, the current studies comprehensively address scale formation mechanisms in gas reservoirs, and the critical knowledge gaps persist regarding design and preparation, structure-activity relationship, and mechanism of action of scale inhibitors in specific environments of gas reservoirs.\u003c/p\u003e \u003cp\u003eCurrently, the scale inhibitor solution with certain concentration was applied to solve the problem of scaling inside the wellbore depends on the combination of functional groups in the scale inhibitor, and the main mechanism is that the combination of functional groups in the scale inhibitor (such as phosphonic acid, carboxylic acid, sulfonic acid, and amide groups) and Ca\u003csup\u003e2+\u003c/sup\u003e to delay the growth of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals and inhibit the formation of CaCO\u003csub\u003e3\u003c/sub\u003e scale. Presently, the scale inhibitors, such as natural polymers, phosphates, copolymers and environmental-friendly types, are widely used\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. Undeniably, the formation of CaCO\u003csub\u003e3\u003c/sub\u003e scale has been effectively reduced to some extent by these traditional types of scale inhibitors, but, there are also some drawbacks that limit its further promotion and application, such as the easy decomposition of natural polymer scale inhibitors at high temperatures\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Besides, the principal limitation of phosphate-based scale inhibitors resides in their propensity to undergo pronounced thermal hydrolysis under high temperature, which subsequently induces aquatic eutrophication through phosphate release\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. Moreover, the copolymer scale inhibitors are further challenged by suboptimal thermal tolerance and non-negligible eco-toxicity, particularly under prolonged operational conditions. Furthermore, the environment-friendly scale inhibitors demonstrate favorable environmental compatibility, but they exhibit compromised scale inhibition efficacy under elevated-temperature conditions\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Recently, some organic scale inhibitors were developed by adding functional groups, such as sulfonic acid groups, which with excellent performance under high temperature. However, the organic scale inhibitors are main used in cooling water circulation system, and the application temperature is basically not more than 100 ℃\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e. Scale inhibition performance under elevated thermal conditions is inherently compromised by structural heterogeneity within organic polymer matrices, resulting in suboptimal or negligible scaling mitigation efficacy\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eMontmorillonite (MMT) functions as an active polymerization filler primarily due to its expandable interlayer spaces, high-aspect-ratio nanolayers, and intrinsic cation-exchange capability, synergistically enhance polymer nucleation and matrix integration. Secondly, which distinct from conventional fillers, such as silica or carbon black, MMT's structural anisotropy facilitates monomer intercalation within its aluminosilicate galleries, enabling in situ exfoliation during polymerization to achieve homogeneous dispersion. Moreover, its superior interfacial interactions with initiators or monomers, coupled with exceptional thermal stability ensure structural integrity under high-temperature polymerization conditions\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. Regarding the problem of poor temperature resistance of the scale inhibitor mentioned above, based on the characteristics of MMT, during this study, a polymerizable quaternary ammonium salt was used to modify montmorillonite, which could use as an active polymerizable filler\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. Then, the intercalated MMT served as reactive filler for synthesizing high-temperature scale inhibitor CT-5 via in-situ polymerization of AMPS, AA, and DMDAAC monomers. Structural characterization (XRD, FTIR, TGA) and mechanistic analysis revealed enhanced thermal stability. This organic-inorganic composite broadens the chemical diversity of scaling inhibitors, establishing a design framework for thermally adaptive materials.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1. Materials\u003c/h2\u003e\n \u003cp\u003e2-acrylamido-2-methylpropanesulfonic acid (AMPS), diallyldimethylammonium chloride (DMDAAC), acrylic acid (AA), sodium bisulfite (NaHSO\u003csub\u003e3\u003c/sub\u003e), potassium persulfate (K\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e) is all analytical grade, which purchased from Kelong Chemical plant (Chengdu, China). Montmorillonite (MMT) is an industrial product, which purchased from Xinjiang Zhongfei Xiazi Street Bentonite Co., Ltd.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2. Synthesis of CT-5\u003c/h2\u003e\n \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.1 Selection of Co-monomers\u003c/h2\u003e\n \u003cp\u003eDue to the presence of long-chain side groups and sulfonic acid groups with good temperature and salt resistance in the molecular structure of AMPS, it has a significant steric hindrance effect and strong coordination effect, which can effectively improve the temperature resistance of polymers. Therefore, AMPS is chosen as the main monomer\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. The carboxylic acid groups in the molecular structure of AA have good coordination and strong electronegativity, and can form complexes with Ca\u003csup\u003e2+\u003c/sup\u003e in the liquid phase, which can not only improve the hydrophilicity and coordination of polymer, but also enhance the scale inhibition performance\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. DMDAAC is a cationic monomer, which can enlarge the layers spacing of montmorillonite, facilitating the insertion and release of polymers\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. As discussed in above, the MMT has the characteristics of layers structure, hydrothermal expansion and high thermal stability\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e, which can not only improve high thermal stability of polymers, but also enhance the scale inhibition effect at high temperature through the polymer intercalation bound release function.\u003c/p\u003e\n \u003cp\u003eThe mechanism of polymer intercalated organic montmorillonite is as follows:\u003c/p\u003e\n \u003cp\u003eRNRʹ\u003csub\u003e3\u003c/sub\u003eX + M-Mont \u0026rarr;RNRʹ\u003csub\u003e3\u003c/sub\u003e-Mont\u0026thinsp;+\u0026thinsp;MX\u003c/p\u003e\n \u003cp\u003e(R\u0026mdash;Organic group; Rʹ\u0026mdash;H; X\u0026mdash;Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e, Br\u003csup\u003e\u0026minus;\u003c/sup\u003e, I\u003csup\u003e\u0026minus;\u003c/sup\u003e; M\u0026mdash;Na\u003csup\u003e+\u003c/sup\u003e, Ca\u003csup\u003e2+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e)\u003c/p\u003e\n \u003cp\u003eThe polymerization reaction of AA/AMPS/DMDAAC is shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, and the preparation process of polymer/montmorillonite is shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.2 The synthesis process of CT-5\u003c/h2\u003e\n \u003cp\u003e\u003cstrong\u003ea\u0026nbsp;\u003c/strong\u003ePretreatment of MMT\u003c/p\u003e\n \u003cp\u003eAdd a certain amount of DMDAAC to a suspension of montmorillonite with a solid content of 5%, and after ultrasonic dispersion, centrifuging, washing, and drying, the pre-treated modified MMT is obtained.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eb\u0026nbsp;\u003c/strong\u003eThe preparation process of CT-5\u003c/p\u003e\n \u003cp\u003eMix a certain amount of pre-treated modified MMT with deionized water and place it into a flask. Then weigh 12.5 g of AMPS, 8.3 g of AA, and 4.2 g of DMDAAC respectively, dissolve the weighed mixed monomers in deionized water (monomer mass fraction is 25%), adjust its pH value to 7, and then pour the mixed solution into the flask. Then, nitrogen was continuously injected for 10 min, stirred at 40 ℃ for 20 min, and then heated to 70 ℃, and 0.6% initiator solution was added. Then, the CT-5 can be obtained after the reaction at this temperature for 5 h and cooling to room temperature. For the subsequent application of scale inhibition and analysis of scale inhibition related mechanisms, the solubility of CT-5 was measured, as a result, the solubility of CT-5 is very good within the temperature range of 70\u0026thinsp;~\u0026thinsp;130 ℃, reaching 100%.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Structure characterization and scale inhibition performance evaluation method of CT-5\u003c/h2\u003e\n \u003cp\u003eThe product obtained after reaction is firstly added to ethanol in batches, and with leaching, drying, grinding, and then dissolved in distilled water. Moreover, the product is leached by acetone to obtain orange powder, which could be used to structure characterization.\u003c/p\u003e\n \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.1 Infrared analysis\u003c/h2\u003e\n \u003cp\u003eThe obtained orange powder was characterized by infrared spectroscopy using a WQF-520 Fourier transform infrared spectrometer (Nicolette, USA) with a scanning range of 400\u0026thinsp;~\u0026thinsp;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.2 Thermogravimetric analysis\u003c/h2\u003e\n \u003cp\u003eThe thermal stability of the powder was analyzed by using the STA449F3 synchronous comprehensive thermal analyzer (NETZSCH, Germany) at a temperature of 50\u0026thinsp;~\u0026thinsp;450 ℃ with the heating rate of 5 ℃/min, and nitrogen atmosphere used.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.3 X-ray diffraction analysis\u003c/h2\u003e\n \u003cp\u003eThe phase composition of the powder was characterized by an X\u0026apos;Pert MPD PRO X-ray diffractometer (Panat, Netherlands) with a tube voltage of 40 kV, a tube current of 40 mA, a scanning rate of 2 \u0026deg;/min, and a scanning range of 1\u0026deg; ~ 10\u0026deg;.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.4 Scale inhibition performance test\u003c/h2\u003e\n \u003cp\u003eDuring this study, the CaCO\u003csub\u003e3\u003c/sub\u003e scale type standard saline water was prepared depending on the method described in SY/T 5673\u0026thinsp;\u0026minus;\u0026thinsp;2020 \u0026quot;General Technical Conditions for Oilfield Scale Inhibitors\u0026quot;, then, the CaCO\u003csub\u003e3\u003c/sub\u003e scale samples were simulated according to the method described in this standard. Furthermore, the scale inhibition rate of CaCO\u003csub\u003e3\u003c/sub\u003e scale was investigated.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.5 Chelation amount and layer spacing test\u003c/h2\u003e\n \u003cp\u003eAfter the experiment on the scale inhibition rate of CT-5 at different temperatures, the reacted solution was centrifuged at high speed, and the free Ca\u003csup\u003e2+\u003c/sup\u003e content in the supernatant was measured to calculate the chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.6 Scanning electron microscope\u003c/h2\u003e\n \u003cp\u003eThe microscopic morphology of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with or without CT-5 was analyzed by using a FlexSEM1000 compact intelligent scanning electron microscope. Before running testing, the gold spraying was required to enhance the conductivity of the sample.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.7 X-ray photoelectron spectroscopy\u003c/h2\u003e\n \u003cp\u003eThe X-ray photoelectron spectroscopy (XPS) is a typical surface analysis method that can qualitatively analyze the elemental composition and chemical state of material surfaces. Moreover, it can quantitatively analyze the elemental content on the surface of materials. Static scale inhibition experiments were conducted, and the adding amount of CT-5 is 0 and 4%. After filtering and separating a small amount of solid in the bottle, it was dried in a vacuum chamber and analyzed for changes in the binding energy of Ca 2p and O 1s orbitals using X-ray photoelectron spectroscopy.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Optimization of preparation conditions of CT-5\u003c/h2\u003e \u003cp\u003eTaking the scale inhibition rate as the main evaluation index, the optimal conditions for the synthesis of CT-5 were optimized, and the orthogonal experiment of copolymerization reaction was designed, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. According to the principle of free radical polymerization, the main factors affecting the properties of co-polymer products are monomer mass ratio A [m (AMPS): m (AA): m (DMDAAC): m (MMT)], reaction temperature B (℃), initiator dosage C (%), reaction time D (h), and solution E (pH). Based on this, a five factor four level orthogonal experiment was constructed to analyze the main factors affecting copolymerization and the optimal synthesis conditions. Here, the \u003cem\u003eK1\u003c/em\u003e\u003csup\u003e\u003cem\u003e*\u003c/em\u003e\u003c/sup\u003e, \u003cem\u003eK2\u003c/em\u003e\u003csup\u003e\u003cem\u003e*\u003c/em\u003e\u003c/sup\u003e, \u003cem\u003eK3\u003c/em\u003e\u003csup\u003e\u003cem\u003e*\u003c/em\u003e\u003c/sup\u003e and \u003cem\u003eK4\u003c/em\u003e\u003csup\u003e\u003cem\u003e*\u003c/em\u003e\u003c/sup\u003e is the average scale inhibition at levels 1, 2, 3 and 4, respectively. Besides, the R is the range between different levels under the same factor conditions.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eOrthogonal experimental table of co-polymerization\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eExperiment number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eExperimental factors\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003escale inhibition ratio (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB(℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eD(h)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eE(pH)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55:30:13:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e77.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55:30:13:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e89.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55:30:13:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e91.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55:30:13:2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e95.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48:25:23:4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e81.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48:25:23:4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e85.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48:25:23:4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e90.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48:25:23:4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e97.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40:30:34:6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e80.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40:30:34:6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e85.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40:30:34:6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e88.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40:30:34:6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e92.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32:15:45:8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e72.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32:15:45:8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e76.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32:15:45:8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e79.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32:15:45:8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e83.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK1*\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e88.475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e77.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e83.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e85.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e84.075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"4\" rowspan=\"5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK2*\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e88.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e84.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e85.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e85.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e85.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK3*\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e86.475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e87.425\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e86.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e85.275\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e86.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK4*\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e77.825\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e85.775\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e85.775\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e85.35\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eR*\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.575\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWhich as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the orthogonal analysis revealed reaction temperature as the predominant factor affecting inhibitor performance (highest range value in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), followed sequentially by monomer mass ratio, initiator dosage (%), pH and reaction time (h). The optimal synthesis protocol (B4A2C3E3D4) derived from orthogonal mean analysis comprised, namely, the reaction temperature is 75 ℃, the monomer mass ratio is 48:25:23:4, the initiator dosage is0.6%, the pH is 7, and the reaction time is 12 h. CT-5 synthesized under these conditions underwent subsequent analytical characterization.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Structural characterization of CT-5\u003c/h2\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Infrared spectrum characterization of CT-5\u003c/h2\u003e \u003cp\u003eThe infrared spectrum characterization results of CT-5 are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, 3477 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is the N-H characteristic peak contained by the amide group in the molecular structure of AMPS, and the stretching vibration absorption peak of -CH\u003csub\u003e3\u003c/sub\u003e is located at about 2936 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The stretching vibration absorption peaks of C\u0026thinsp;=\u0026thinsp;O in AA and AMPS are located at about 1724 and 1655 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. The deformation vibration stretching peak of N-H is located at about 1552 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the stretching vibration absorption peaks of C-N in AMPS and DMDAAC are located at about 1438 and 1368 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The stretching vibration absorption peaks of SO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e are located at about 1230, 1043, and 1175 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. At 630 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is the deformation vibration peak of C-N five-membered ring in DMDAAC. However, compared to P (AA/AMPS/DMDAAC), the infrared spectrum of CT-5 shows distinct peaks at 1106 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 463 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with the peak at 1106cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e being the stretching vibration peak of Si-O and the peak at 463cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e being the bending vibration peak of Si-O\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. It can be seen from the above analysis that the functional groups of three monomers and MMT appear in the spectrum, which indicates that the polymer and MMT are successfully combined, and the CT-5 is the target product.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e\u003cem\u003e3.2.2 XRD Characterization of CT-5\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe XRD characterization results of MMT and scale inhibitor CT-5 are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFrom Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, it can be seen that the layer spacing of MMT is 1.208 nm (2\u003cem\u003eθ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;7.31). The diffraction peak of CT-5 shifted to the left and the intensity significantly decreased, and the peak shape showed a wide and diffuse raised package shape, with an increased interlayer spacing of 1.522 nm (2\u003cem\u003eθ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;5.80). According to the literature\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e, when the interlayer spacing increases beyond the small angle X-ray diffraction range, only the intercalated portion can be diffracted. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows a decrease in the intensity of the CT-5 diffraction peak, indicating that the polymer has been successfully intercalated between the layers of MMT, forming a composite material with an intercalation structure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e3.2.3 Thermal stability analysis of CT-5\u003c/h2\u003e \u003cp\u003eThe thermal stability analysis of CT-5 is listed in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb shows the initial thermal decomposition temperature of P (AMPS/AA/DMDAAC) and CT-5 is about 218.42 and 235.24 ℃. The above phenomenon indicates that the addition of MMT significantly improves the thermal stability of CT-5, making the composite intercalated polymer CT-5 have good temperature resistance and resistance characteristics. On the one hand, it is due to the excellent thermal stability of MMT. On the other hand, due to the intercalation of the polymer between the layers of MMT, the layers not only can effectively shield thermal decomposition effects, but also hinder the movement of small molecules generated by polymer molecules during thermal decomposition. Therefore, CT-5 exhibits good thermal stability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Performance evaluation of CT-5 application\u003c/h2\u003e \u003cdiv id=\"Sec22\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Scale inhibition effect of CT-5 at high temperature\u003c/h2\u003e \u003cp\u003eExcellent scale inhibition performance at high temperature is the main performance indicator of high temperature scale inhibitors, however, polymer scale inhibitors are prone to functional group decomposition, molecular chain breakage, and high-temperature desorption under high temperature conditions, resulting in a significant reduction or even complete loss of scale inhibition effect. In this section, the scale inhibition rates are tested at different temperature points and CT-5 dosage to investigate the scale inhibition performance of CT-5 at high temperatures, and the results are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe scale inhibition rate at different temperature and different CT-5 dosage\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eScale inhibitor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e70℃\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003e90℃\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e110℃\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c13\" namest=\"c11\"\u003e \u003cp\u003e130℃\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e6%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e2%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003e4%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003e6%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP(AMPS/AA\u003c/p\u003e \u003cp\u003e/DMDAAC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e87.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e93.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e91.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e80.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e84.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e82.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e70.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e77.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e64.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e43.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e59.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e52.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCT-5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e85.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e89.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e81.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e85.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e83.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e76.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e82.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e80.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e68.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e73.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e70.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWhich as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, on the one hand, the scale inhibition rates of P(AMPS/AA/DMDAAC) and CT-5 show a trend of first increasing and then decreasing with the increase of dosage, the scale inhibition rate of P(AMPS/AA/DMDAAC) and CT-5 with 4% adding amount is 93.6 and 89.7% at the temperature of 70 ℃, of course, which shows similar patterns at other temperatures ( the adding amount will be used for subsequent evaluation and mechanism research experiments). Moreover, it was also demonstrated that the scale inhibition rate of CT-5 is slightly lower than that of P(AMPS/AA/DMDAAC) at low temperature, such as 70 ℃, which may due to the layered structure of MMT in CT-5 affecting the chelating ability of anionic groups to Ca\u003csup\u003e2+\u003c/sup\u003e. However, it was also demonstrated that the scale inhibition rate of CT-5 is higher than that of P(AMPS/AA/DMDAAC) at high temperature, the scale inhibition rate of CT-5 with 4% adding amount is higher than that of P(AMPS/AA/DMDAAC) by 1.2, 4.7 and 14.1% at the temperature of 90, 110 and 130 ℃, respectively. Besides, the scale inhibition rate of P(AMPS/AA/DMDAAC) decreases from 93.6\u0026ndash;59.3%, a decrease of 34.3% was observed, while the scale inhibition rate of CT-5 decreases from 89.7\u0026ndash;73.4%, a decrease of only 16.3%. Based on the data from the above two aspects, CT-5 has the good high-temperature resistance performance.\u003c/p\u003e \u003cp\u003eAdditionally, which as discussed above, the scale inhibition rates of CT-5 with 4% adding amount is larger than that 2 and 6% at the temperature of 110 and 130 ℃, the main reason is that scale inhibitors form soluble complexes by combining functional groups (such as sulfonic acid and carboxylic acid groups) with scaling ions (such as Ca \u0026sup2; ⁺) to inhibit crystal growth, and when the adding amount of CT-5 is 4%, the molar ratio of CT-5 molecules to Ca\u003csup\u003e2+\u003c/sup\u003e approaches stoichiometric equilibrium, achieving maximum complexation efficiency. However, exceeding the optimal concentration (6%), excessive CT-5 molecules may compete for binding sites or form molecular aggregates, thereby reducing effective activity. Simultaneously, the reason for scale inhibition rates of CT-5 decreased when the temperature beyond 130 ℃ is that high temperature causes thermal cracking of active functional groups (such as sulfonic acid groups and carboxylic acid groups) and molecular main chains in CT-5 molecules, on the other hand, the high temperatures may also intensify the thermal motion of polymer chains, leading to disordered molecular conformation and masking of active sites of CT-5, resulting in a decrease in scale inhibition effectiveness.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2 Evaluation of salt resistance of CT-5\u003c/h2\u003e \u003cp\u003eThe high mineralization environment in deep and ultra deep wells can affect the extension of polymer molecular chains, causing a sharp change in the scale inhibition effect of scale inhibitors. Therefore, scale inhibitors need to have excellent salt resistance performance. In this section, the scale inhibition rate of CT-5 was measured at 130 ℃ with different NaCl contents to investigate the salt resistance performance of CT-5, and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows that the scale inhibition rate of CT-5 presents a trend of first increasing and then stabilizing with the increase of NaCl content, and the scale inhibition rate of CT-5 with 4% adding amount is 73.4 and 76.9% by the salt content of 0 and 8%, and the change rate is 4.76%. Besides, when the NaCl content is less than 4%, the scale inhibition rate of CT-5 increases significantly with the increase of NaCl content, but when the NaCl content exceeds 4%, the scale inhibition rate of CT-5 increases slowly and tends to be stable with the increase of NaCl content, which is consistent with relevant literature\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. The reason for the above phenomenon may be related to the molecular structure of the scale inhibitor. Due to the presence of both cationic and anionic groups in polymer molecules, there are two types of binding interactions within and between molecules. The shielding effect of NaCl hinders the binding interactions within and between the molecules, making the molecular chains of the polymer to unfold, enhancing the adsorption and chelation effects of molecular chains, disrupting the normal growth of scale crystals and increasing the scale inhibition rate\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Study on scale inhibition mechanism of CT-5 at high temperature\u003c/h2\u003e \u003cp\u003ePresently, it is believed that the scale inhibition mechanism of scale inhibitors as follows\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. At first, the anionic groups within scale inhibitor molecules form soluble chelate complexes with scale-forming cations, such as Ca\u0026sup2;⁺ in aqueous solutions, thereby inhibiting crystalline growth and exerting their scale inhibiting function. Moreover, through adsorption onto scale microcrystal surfaces, these anionic groups establish electrical double layers that generate surface electrostatic repulsion, which effectively preventing microcrystal aggregation into macroscopic deposits. Furthermore, scale inhibitors disrupt the regular lattice arrangement during crystal growth, inducing lattice strain that weakens structural integrity and promotes crystalline fragmentation, ultimately achieving scale inhibition through mechanical destabilization.\u003c/p\u003e \u003cp\u003eIn this part, the release mechanism of CT-5 at high temperature and its effect on the crystal structure of CaCO\u003csub\u003e3\u003c/sub\u003e scale were studied by measurement of chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e at different temperatures, XRD, SEM and XPS tests, and then the scale inhibition mechanism of CT-5 was further studied.\u003c/p\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003e3.4.1 Release mechanism of CT-5 at high temperature\u003c/h2\u003e \u003cp\u003eTo investigate the scale inhibition mechanism of CT-5, the changes in layer spacing and Ca\u003csup\u003e2+\u003c/sup\u003e chelation amount of CT-5 at different temperatures were measured, and then compared with the chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e by P(AA/AMPS/DMDAAC), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhich as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the results show that the interlayer spaces of CT-5 gradually increase with the increase of temperature, which is caused by thermal expansion of the layers of MMT in the CT-5 at high temperatures, the interlayer spaces increased by 63.49% when the temperature rises from 80 to 130 ℃. Then, it was also found that the chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e by P(AMPS/AA/DMDAAC) and CT-5 decreases with the increase of temperature, the reason is that the chelating groups of polymer molecules have a dynamic equilibrium process of adsorption and desorption. Specifically, at high temperature, it is manifested as a decrease in the chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e when the desorption effect is greater than the adsorption effect. But the decreasing trend of the chelating amount of Ca\u003csup\u003e2+\u003c/sup\u003e by CT-5 with increasing temperature is significantly slower than that of P(AMPS/AA/DMDAAC), which indicating that CT-5 is less sensitive to temperature. The reason is that the layer spacing of MMT expands by thermal expansion, the thermal motion of polymer molecules intensifies, and the polymer molecules originally curled up between the MMT layers is gradually released with the increase of the layer spacing, causing an increase of effective adsorption groups. Therefore, the CT-5 has a higher chelation amount to Ca\u003csup\u003e2+\u003c/sup\u003e, as a result, the trend of decreasing the chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e with increasing temperature is slower.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section3\"\u003e \u003ch2\u003e3.4.2 Effect of CT-5 on the crystal structure of CaCO\u003csub\u003e3\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eThe effect of CT-5 on the crystal structure of CaCO\u003csub\u003e3\u003c/sub\u003e scale was analyzed by XRD, and compared with the original CaCO\u003csub\u003e3\u003c/sub\u003e scale. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e8\u003c/span\u003e shows the XRD analysis results of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with and without CT-5.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAccording to the XRD analysis of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in the solution without CT-5 shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e8\u003c/span\u003e, only the characteristic diffraction peaks of CaCO\u003csub\u003e3\u003c/sub\u003e (calcite) are observed at 23.2\u0026deg;, 29.4\u0026deg;, 31.5\u0026deg;, 36.3\u0026deg;, 38.5\u0026deg;, 43.0\u0026deg;, 47.2\u0026deg; and 47.9\u0026deg;\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. At the same time, the diffraction peak at 29.4\u0026deg; is sharper and higher than others, indicating that the CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals mainly grew along this crystal plane. The XRD analysis of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with CT-5 in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e8\u003c/span\u003e shows that the characteristic diffraction peak of CaCO\u003csub\u003e3\u003c/sub\u003e (calcite) only appears at 23.2\u0026deg;, the characteristic diffraction peak of CaCO\u003csub\u003e3\u003c/sub\u003e (aracharite) appears at 36.0 and 47.6\u0026deg;\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. Unlike the XRD results of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution without CT-5, the XRD analysis spectrum of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with CT-5 shows characteristic diffraction peaks of CaCO\u003csub\u003e3\u003c/sub\u003e (aragonite) with the character of loose structure and easy physical damage at 21.0\u0026deg;, 25.0\u0026deg;, 27.1\u0026deg;, 32.8\u0026deg;, 39.5\u0026deg; and 43.2\u0026deg;\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. The characteristic peaks belonging to both CaCO\u003csub\u003e3\u003c/sub\u003e (calcite) and CaCO\u003csub\u003e3\u003c/sub\u003e (aragonite) decrease significantly, indicating that the main component in the crystal is CaCO\u003csub\u003e3\u003c/sub\u003e (vaterite). On the one hand, the anion group in CT-5 can not only bind with Ca\u003csup\u003e2+\u003c/sup\u003e, hindering the binding of Ca\u003csup\u003e2+\u003c/sup\u003e with other anions such as CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e. On the other hand, the CT-5 can also change the crystal structure of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals and affect the growth of crystals, thereby improving the scale inhibition effect\u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section3\"\u003e \u003ch2\u003e3.4.3 Analysis of the effect of CT-5 on the crystal morphology of CaCO\u003csub\u003e3\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eThe CaCO\u003csub\u003e3\u003c/sub\u003e crystals primarily as calcite (rhombohedral), aragonite (acicular), and vaterite (spheroidal aggregates with polydispersity)\u003csup\u003e[\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e. SEM analysis revealed CT-5-induced morphological modification of CaCO\u003csub\u003e3\u003c/sub\u003e deposits, elucidating its scale inhibition mechanism. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003e contrasts the crystallographic features of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with and without CT-5. The magnification used in the SEM of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals without CT-5 is 2000, 4000 and 10000, the magnification used in the SEM of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with 2.0% CT-5 is 1000, 4000 and 10000, the magnification used in the SEM of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals with 4.0% CT-5 is 1000, 2000 and 4000, which has been also added in the revised manuscript.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003ea shows the CaCO\u003csub\u003e3\u003c/sub\u003e scale crystal without adding CT-5 is regular cubic shape with dense structure, indicating that the type of CaCO\u003csub\u003e3\u003c/sub\u003e crystals is calcite. However, Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003eb and Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003ec show that the morphology of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals changes significantly after the addition of CT-5. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003eb shows that when the content of CT-5 is 2%, most CaCO\u003csub\u003e3\u003c/sub\u003e crystals appear as irregular angular shapes, only a small number of CaCO\u003csub\u003e3\u003c/sub\u003e crystals appear as rod-shaped, and there are almost no regular cubic CaCO\u003csub\u003e3\u003c/sub\u003e crystals. As the content of CT-5 increases, the morphology of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals continues to be changed. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003ec shows that when the content of CT-5 increases to 4%, the size of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals varies and the crystals are irregular spherical, indicating that the type of CaCO\u003csub\u003e3\u003c/sub\u003e crystals are vaterite. In addition, it can be clearly seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e9\u003c/span\u003ec\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e that there are obvious cracks on the surface of CaCO\u003csub\u003e3\u003c/sub\u003e crystals, indicating that the structure of CaCO\u003csub\u003e3\u003c/sub\u003e crystal is relatively loose, which is consistent with the description of the unstable thermodynamic state and structure of vaterite in the literature\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. The above characterization results indicate that the CT-5 achieves scale inhibition by changing the crystal structure of CaCO\u003csub\u003e3\u003c/sub\u003e, which may due to the anionic groups of CT-5 adsorbing on the surface of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals by chelation of Ca\u003csup\u003e2+\u003c/sup\u003e and electrostatic interactions, occupying the growth active sites of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals\u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e, causing lattice distortion of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystal and achieving the scale inhibition effect.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec28\" class=\"Section3\"\u003e \u003ch2\u003e3.4.4 Chemical binding energy analysis of CT-5 on CaCO\u003csub\u003e3\u003c/sub\u003e crystals\u003c/h2\u003e \u003cp\u003eXPS revealed CT-5-induced chemical binding energy modulation in CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, elucidating its inhibition mechanism\u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e10\u003c/span\u003e compares the XPS spectra of CaCO\u003csub\u003e3\u003c/sub\u003e deposits in scale-inhibited and control systems, namely, the XPS results of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with and without scale inhibitor CT-5.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e10\u003c/span\u003e (a), only energy peaks of elements Ca, C and O appear in the XPS spectrum of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution without CT-5, however, in the XPS spectrum of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in the solution with CT-5, in addition to the energy peaks of elements Ca, C, and O, there are also energy peaks of elements N (391.5 eV) and S (169.3 eV), which may be resulting from the raw materials AMPS and DMDAAC. The high-resolution spectrum of Ca 2P in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e10\u003c/span\u003e (b) shows that energy peaks belonging to Ca 2p1/2 and Ca 2p3/2 of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution without CT-5 appear at 350.6 and 347.1 eV, respectively\u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. The energy peak positions ascribed to Ca 2p1/2 and Ca 2p3/2 in CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with CT-5 are 350.1 and 346.7 eV, respectively. Compared with high-resolution spectrum of Ca 2P in CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution without CT-5, the binding energy of Ca 2P in CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals in solution with CT-5 has shifted to a lower binding energy direction by 0.5 eV. This indicates that the CT-5 can change the chemical environment of element Ca, because the anionic groups in CT-5 will bind with Ca\u003csup\u003e2+\u003c/sup\u003e, transfer and contribute some electrons to Ca\u003csup\u003e2+\u003c/sup\u003e, thereby increasing the electron density of the outer layer of Ca, and causing a decrease in the binding energy of Ca\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e. The above experimental results show that the anionic groups in CT-5 are bound to Ca\u003csup\u003e2+\u003c/sup\u003e, thus hindering the scale formation of Ca\u003csup\u003e2+\u003c/sup\u003e and other anions, and inhibiting the normal growth of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec29\" class=\"Section3\"\u003e \u003ch2\u003e3.4.5 Scale inhibition mechanism of CT-5 at high temperature\u003c/h2\u003e \u003cp\u003eAccording to the molecular chain of polymer P(AA/AMPS/DMDAAC) and the structure of MMT in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, it can be seen that CT-5 has good high temperature resistance due to the high temperature resistance of MMT layer, as well as the existence of five membered ring structures of polymer molecular chain and the group of sulfonic acid root in molecular side chain. By studying the effect of temperature on the layer spacing of CT-5 and the chelation amount of Ca\u003csup\u003e2+\u003c/sup\u003e, it can be seen that the higher the temperature and the larger the layer spacing, the more scale inhibiting groups in free fluid, indicating that CT-5 can release different amounts of scale inhibiting groups at different temperatures. By utilizing the characteristics of the MMT layer and thermal expansion, CT-5 with good scale inhibition performance at high temperatures. By analyzing the effect of CT-5 on the structure of CaCO\u003csub\u003e3\u003c/sub\u003e crystal scale through XRD, SEM and XPS, combined with the molecular structure of CT-5, it can be inferred that the sulfonic acid and carboxylic acid groups with strong coordination in the polymer will form chelates with free Ca\u003csup\u003e2+\u003c/sup\u003e in solution. On the one hand, the concentration of Ca\u003csup\u003e2+\u003c/sup\u003e in free liquid is reduced, and the probability of Ca\u003csup\u003e2+\u003c/sup\u003e binding with CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and other scale ions is reduced. On the other hand, the anionic groups of CT-5 adsorbing on the surface of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, hindering the normal growth of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, changing the lattice structure of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, and achieving scale inhibition effect\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e. Besides, the scale inhibition mechanism of CT-5 is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e11\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eDuring this study, the organic-inorganic composite scale inhibitor CT-5 was successfully synthesized via solution polymerization-mediated in situ intercalation using AA, AMPS and DMDAAC as monomers, with MMT as reactive filler. The optimized preparation process parameters include a reaction temperature of 75 ℃, an initiator dosage of 0.6%, a solution pH of 7, a reaction time of 12 h, and a monomer ratio of m (AMPS): m (AA): m (DMDAAC): m (MMT)\u0026thinsp;=\u0026thinsp;48:25:23:4. The results of FTIR, XRD, and TG-DTG shows that the CT-5 intercalated MMT was successful, which shows a composite intercalation structure of organic polymer/inorganic montmorillonite, and the initial thermal decomposition temperature CT-5 was increased to 235.24 ℃. Performance evaluation of CT-5 application shows that CT-5 has the good high-temperature resistance performance, a decrease of only 16.3% was observed with the temperature increased from 70 to 130 ℃, meanwhile, the scale inhibition rate of CT-5 presents a trend of first increasing and then stabilizing with the increase of NaCl content (0\u0026thinsp;~\u0026thinsp;8%). Furthermore, the results of release mechanism of CT-5 at high temperature, effect of CT-5 on the crystal structure and morphology of CaCO\u003csub\u003e3\u003c/sub\u003e show that the interlayer space of MMT in CT-5 molecules expands at higher temperatures (90\u0026thinsp;~\u0026thinsp;130 ℃), and the polymer molecules in the intercalation are released, thus increasing the free adsorption groups, reducing the content of Ca\u003csup\u003e2+\u003c/sup\u003e in the free liquid by forming a complex with Ca\u003csup\u003e2+\u003c/sup\u003e, and inhibiting the normal growth of CaCO\u003csub\u003e3\u003c/sub\u003e crystals to achieve scale inhibition effect. On the other hand, the anionic groups of CT-5 adsorbing on the surface of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, hindering the normal growth of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, changing the lattice structure of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, and achieving scale inhibition effect.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData Availability/ Availability of Data and Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBojian Zhang:\u003c/strong\u003e Data curation, Formal analysis, Writing - original draft. \u003cstrong\u003eYouquan\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eLiu:\u003c/strong\u003e Supervision, Writing - review \u0026amp; editing. \u003cstrong\u003eYing Xiong:\u003c/strong\u003e Supervision, Writing - review \u0026amp; editing. \u003cstrong\u003eCheng Fu:\u003c/strong\u003e Supervision, Validation, Investigation. \u003cstrong\u003eXianbing Wang:\u003c/strong\u003e Data curation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe research is financially supported by Sichuan Province Science and Technology Plan Project (No. 2023YFG0092).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFang, F. et al. 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Manage.\u003c/em\u003e \u003cb\u003e210\u003c/b\u003e, 273\u0026ndash;279 (2018).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"High temperature scale inhibitor, Organic-inorganic composite, Water-gas reservoirs, Interlayer space, CaCO3 scale crystals, Scale inhibition mechanism","lastPublishedDoi":"10.21203/rs.3.rs-5131887/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5131887/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, based on the escalating demand for thermally stable scale inhibitors in high-pressure /high-temperature (HPHT) water-gas reservoirs, an organic-inorganic composite scale inhibitor (CT-5) was successfully synthesized via solution polymerization-mediated in situ intercalation using acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and diallyldimethylammonium chloride (DMDAAC) as monomers, with surface-modified montmorillonite (MMT) as reactive filler. Orthogonal optimization established ideal synthesis parameters, which including a reaction temperature of 75 ℃, an initiator dosage of 0.6%, a solution pH of 7, a reaction time of 12 h, and a monomer ratio of m (AMPS): m (AA): m (DMDAAC): m (MMT)\u0026thinsp;=\u0026thinsp;48:25:23:4. Moreover, the molecular structure and thermal stability of CT-5 were characterized by FTIR, XRD, and TG-DTG, as a result, the polymer intercalated MMT was successful, and CT-5 had a composite intercalation structure of organic polymer/inorganic montmorillonite, with a thermal decomposition temperature of 235.24 ℃. Salt tolerance evaluation demonstrated robust performance under saline conditions. The scale inhibition mechanism of CT-5 was explored through scale inhibition rate testing, interlayer spacing testing at different temperatures, characterization of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystal structure and morphology, and chemical binding energy testing of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals. The CT-5 can release effective chelating groups in the intercalation layer at high temperature, which inhibits the formation of CaCO\u003csub\u003e3\u003c/sub\u003e scale by chelating Ca\u003csup\u003e2+\u003c/sup\u003e to form chelates, and also forms an adsorption layer on the surface of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals to interfere with the normal growth of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals and change the lattice structure of CaCO\u003csub\u003e3\u003c/sub\u003e scale crystals, thereby achieving the scale inhibition effect.\u003c/p\u003e","manuscriptTitle":"Preparation and performance evaluation of polymer intercalated montmorillonite composite high temperature scale inhibitor","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-10 16:36:21","doi":"10.21203/rs.3.rs-5131887/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Accepted","date":"2025-04-24T03:25:32+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-23T10:34:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-19T12:39:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"131927176830715658489080190465562800130","date":"2025-04-10T08:59:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"68672454047084643627458885739985598436","date":"2025-04-10T08:20:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-10T08:18:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"74368345430923276311831803480413318987","date":"2025-04-10T08:00:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"331594499544852927808861942625948908773","date":"2025-04-10T07:34:55+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-09T16:12:30+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-08T17:15:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-08T07:08:15+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cb2b2a43-e60b-4bb6-867e-35de8ba9ab03","owner":[],"postedDate":"April 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":46927245,"name":"Physical sciences/Energy science and technology/Fossil fuels"},{"id":46927246,"name":"Physical sciences/Chemistry/Energy"},{"id":46927247,"name":"Physical sciences/Engineering/Chemical engineering"}],"tags":[],"updatedAt":"2025-05-12T16:05:00+00:00","versionOfRecord":{"articleIdentity":"rs-5131887","link":"https://doi.org/10.1038/s41598-025-99968-9","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-05-07 15:57:17","publishedOnDateReadable":"May 7th, 2025"},"versionCreatedAt":"2025-04-10 16:36:21","video":"","vorDoi":"10.1038/s41598-025-99968-9","vorDoiUrl":"https://doi.org/10.1038/s41598-025-99968-9","workflowStages":[]},"version":"v1","identity":"rs-5131887","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5131887","identity":"rs-5131887","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}