Surface modification of astralenes for obtaining optical composites based on photocurable acrylates

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Tarasov, Julia A. Burunkova, Vera E. Sitnikova, Sergey A. Karpov, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4866698/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Mar, 2025 Read the published version in Polymer Bulletin → Version 1 posted 7 You are reading this latest preprint version Abstract Polymers are a promising matrix for creating optical materials due to the possibility of imparting new properties to the material by introducing additives. In particular, astralenes, which are multilayer toroidal nanostructures, known as structure modifiers for some medium and also have nonlinear optical properties. Hower, the creation of an optical composite requires modification of the particle surface for uniform distribution of particles in the matrix. The two-stage modification technique developed by the authors allows reducing the amount of disordered carbon in the astralenes, as well as making them compatible with photocurable acrylic monomers. As a result, a transparent optical composite was obtained by photopolymerization. The success of the modification process is confirmed by the results of Raman and FTIR spectroscopy, TG analysis. The TEM method showed that the toroidal structure of the particles is preserved after the modification process. The study compared composites with 0.01, 0.05, 0.10%wt. astralenes and the original copolymer. It was found that the introduction of particles into the reaction mass reduces the polymerization rate by more than 40%. At the same time, the conversion degree in samples with and without astralenes is comparable. The transparency of the obtained composites in the visible region and NIR is comparable to the copolymer and is equal to ~ 90%. The introduction of astralenes in the selected concentrations does not significantly affect the optical band gap of the material. Astralenes acrylates photopolymerization optical composite Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Composite materials, including polymer optical nanocomposites, are becoming increasingly widespread. Their distribution is due to two advantageous features: the ability to impart a wide range of properties to the polymer matrix by doping it with a number of functional additives, as well as the ability to create flexible films and complex-shaped coatings. Among polymers, acrylates are the most suitable for producing optical elements due to their transparency in the visible range, chemical stability, and resistance to UV radiation. Some acrylates are also capable of photo-initiated polymerization, which allows creating photonic structures [ 1 ]. One of the disadvantages of optical polymer materials is their lower thermal stability and strength characteristics compared to classic inorganic glasses. The solution to this problem is to modify the polymer matrix with structuring fillers, such as carbon nanoparticles. Among the wide range of carbon structures, a relatively little-studied form, astralenes, is of interest. Astralenes are carbon multilayer nanostructures of toroidal shape obtained by the electric arc method, individual layers of which are formed by a combination of penta- and hexagonal cycles, the average size varies from 15 to 100 nm [ 2 ]. These structures have an anisotropic shape, high surface energy, when an electric field is applied, they are capable of polarizing with the formation of dipoles [ 2 ]. The ability of astralenes to be a structural modifier of various media, a modifier of electrical conductivity, mechanical properties, and thermal stability of materials based on epoxy resins, to act as microcrack stoppers and a reducer of moisture absorption in materials has been proven [ 3 , 4 ]. Moreover, the semiconductor and nonlinear optical properties for this form of carbon are known [ 5 , 6 , 7 ], This determines the interest in studying optical composites based on them. It is worth noting that the efficiency of using astralenes, like other carbon nanoparticles, as modifying agents is limited by their fairly high tendency to agglomerate, leading to uneven distribution in the polymer volume [ 4 ]. The classic way to solve this problem is particles surface modification. It is known that surface modification can be carried out by introducing a surfactant or by chemically attaching structural groups to the surface of the astralene. However, a shell of chemically grafted groups is usually more resistant to physical and chemical influences, so it is more preferable for our research. Nonetheless, in some cases, the grafting of oxygen-containing groups may be insufficient to effectively prevent particle aggregation. The affinity of particles to the medium can be increased by attaching organic chains with a complex structure to the locations of oxygen-containing functional groups. For example, work [ 10 ] shows the possibility of modifying graphene oxide by reacting its particles with ethylenediamine in a 2-butanol solution with heating and stirring. As a result of the reaction, chains containing a terminal amino group are attached to the surface of graphene oxide particles. Work [ 11 ] describes a number of methods for modifying the surface of astralenes: oxidative treatment, [3 + 2] cycloaddition according to the Prato reaction, reaction with diazonium salts, reaction with hydrazine. Based on the above, for effective modification of particles, our research group selected a technique consisting of an oxidative stage and a subsequent stage of treating the particles with a diazonium salt. It is worth noting that modification of the astralene surface, in addition to reducing coagulation, can provide some compensation for the disruption of the conjugated bond system in places of structural defects. Since astralene particles consist of folded graphene sheets, like carbon nanotubes, these layers are characterized by a system of conjugated bonds that provide many unique properties of these particles. Unfortunately, defects in the structure lead to a decrease in the quality of the conjugated system. Therefore, the authors suggested that it is preferable to attach substituents to the astralene surface, which, due to the peculiarities of their structure, have the ability to be integrated into the system of conjugated bonds of the astralene. Thus, the goal of this study is to obtain surface modified astralenes compatible with photocurable acrylic monomers to create an optical polymer medium. Experimental section Materials In the course of the study, carbon nanoparticles – astralenes [ 2 ] were used. For their modification, the following were used: sulfuric acid 92% (CAS#:7664-93-9), potassium permanganate (CAS#:7722-64-7), diisopropylethylamine (CAS#:7087-68-5), methylene chloride (CAS#:75-09-2), procaine hydrochloride (CAS#:51-05-8), sodium nitrite (CAS#:7632-00-0), hydrochloric acid 36% (CAS#: 7647-01-0), ethyl alcohol (CAS#:64-17-5), distilled water. The following monomers were used to create the polymer matrix: ethylene glycol phenyl ether acrylate (2-phenoxyethyl acrylate) (CAS#:48145-04-6), bisphenol A glycerate (CAS#:4687-94-9), 2-carboxyethyl acrylate (CAS#:24615-84-7), in the ratio: 6:3:1. The photoinitiator bis(cyclopentadienyl)bis[2,6-difluoro-3-(1-pyrryl)phenyl] titanium (Irgacure 784) (CAS No. 125051-32-3) was used as a source of free radicals. Modification of astralenes Oxidative modification of astralenes (Astr) was carried out under conditions of interphase catalytic oxidation [ 9 ]. Methylene chloride was used as the organic phase, and a saturated solution of potassium permanganate in an aqueous solution of sulfuric acid (pH = 1) was used as the aqueous phase. Diisopropylethylamine was used as a catalyst. Oxidation of carbon particles was carried out in a round-bottomed flask with a reflux condenser, at the boiling point of the organic solvent, for 1 hour. After that, the remaining permanganate was decomposed with sodium nitrite, and methylene chloride was distilled from the flask. Then the particles were washed to a neutral wash and dried at 105 ℃. Further modification was performed by interaction of oxidized astralene particles (Astr_Ox) with diazonium salt obtained from procaine hydrochloride. For this purpose, oxidized astralenes were introduced into the reaction mass before the synthesis. The synthesis of diazonium salt was executed in a classical way: by portionwise addition of sodium nitrite solution into acidified procaine solution while stirring in a beaker. In this case, the process temperature should not exceed 5℃, and the acidity of the medium should be pH ~ 1, to avoid decomposition of diazonium salt and formation of by-products of organic synthesis. After completion of the diazotization reaction, the beaker was subjected to ultrasonic treatment (~ 10 minutes, frequency 35 kHz, power 55 W) until the release of gas bubbles – nitrogen, which is a decomposition product of diazonium salt, ceased. The modification process scheme is shown in Fig. 1 . After ultrasonic treatment, the particles were precipitated by centrifugation, washed to neutral wash and dried at a temperature of 105 ℃. Transmission electron microscopy of astralenes Suspended in 70% ethanol astralene particles were placed on copper slot grids covered with pioloform film, dried, and observed on the transmission electron microscope JEM 1400 (Jeol company) at accelerating voltage of 80 kV. Raman spectroscopy of astralenes The structure of astralenes before and after modification was studied using a Renishaw ‘inVia’ micro-Raman spectrometer in the range 4000–400 cm − 1 with a laser wavelength of 488 nm. FTIR spectroscopy of astralenes The FTIR spectra of the samples were recorded using a Bruker Tensor 37 FTIR spectrometer. The FTIR transmission spectra of astralene particles were obtained using a standard potassium bromide pellet preparation technique in the 4000–400 cm − 1 range with a resolution of 2 cm − 1 and averaging over 32 scans. Study of astralenes influence on polymerization The effect of the modified astralene particles on the photopolymerization of acrylates was studied by FTIR spectroscopy using a Pike MIRacle ATR attachment with a diamond-coated zinc selenide crystal in the 4000–600 cm − 1 range, a spectral resolution of 2 cm − 1 and averaging over 5 scans. These instrument settings allowed recording a series of measurements with a time resolution of 7.5 seconds between spectra. Study of astralenes thermal destruction Thermal properties of the initial and modified astralenes were studied using a NETZSCH TG 209 F1 Libra thermogravimetric analyzer in the range of 25–900°C at a heating rate of 3°C/min in a nitrogen environment. Preparation of polymer composite Particles of modified astralene were used to create an optical composite based on acrylates. For this purpose, a suspension of modified astralenes in ethanol was obtained by ultrasonic treatment (treatment time: 10 minutes, frequency 35 kHz, power 55 W). After that, the suspension was introduced into a mixture of bisphenol A glycerate and 2-carboxyethyl acrylate. The samples were heated to 50 ℃ with stirring until the ethanol was completely removed, then ethylene glycol phenyl ether acrylate was added. After the photoinitiator Irgacure 784 was introduced into the mixture in an amount of 0.5% of the monomer mass. The content of astralenes in the mixtures varied and amounted to 0.01, 0.05 and 0.10%wt. of the monomer mass. Measurement of polymer composites transparency The influence of astralene particles on the transparency of the polymer material was assessed using a Unico UV spectrometer (USA) in the range of 190–1100 nm with a resolution of 1 nm. Results and discussion Research of modified astralenes After modification, the initial and surface-modified particles (Astr_Mod) of astralenes were examined by transmission electron microscopy. The obtained images of the astralene particles are shown in Fig. 2 . As can be seen from Fig. 2 A, the original astralenes are toroidal structures demonstrating a high tendency to agglomeration. The size of individual particles varies in the range from 20 to 90 nm. From the image of modified astralenes (Fig. 2 B), it is evident that after modification, the particles are not destroyed and retain a toroidal shape, the sizes of individual particles are in the same range as the sizes of the original ones. The initial and oxidized astralenes were studied by Raman spectroscopy to assess the efficiency of the oxidative modification stage. The obtained spectra are presented below (Fig. 3 ). Three peaks are clearly visible in the spectra of the initial and oxidized astralenes: 2710 cm − 1 , 1580 cm − 1 , 1355 cm − 1 , known as 2D, G and D bands. From Fig. 3 it is evident that after the oxidative treatment, the intensity of the D band (1355 cm − 1 ), related to the vibration of the edge and defective areas in the structure, i.e. disordered carbon, decreases, and an increase in the intensity of the G band (1580 cm − 1 ), related to the vibration of bonds in the graphene sheet, is also observed. The ratio of the D and G bands changes from 0.4758 for the initial particles to 0.2980 for the oxidized particles. This result, as expected, indicates a decrease in the content of disordered carbon from the sample composition. Also, in both samples, an intense 2D band (2710 cm − 1 ) is observed, indicating that the studied particles consist of several graphene layers [ 13 ]. It should be noted that the Raman spectroscopy method at an excitation wavelength of λ = 488 nm is not applicable for studying modified astralenes, since the presence of organic groups on the surface of the particles causes them to luminesce. The initial, oxidized and modified astralenes were studied using FTIR spectroscopy (in transmission mode), for which potassium bromide-based tablets of samples were prepared (Fig. 4 ), which made it possible to evaluate the effectiveness of the modification process. From Fig. 4 it is evident that the initial astralenes are characterized by the presence of a band at 2960 cm − 1 , which is related to the asymmetric stretching vibrations of the C-H bond in the -CH 3 group, the bands at 2920 and 2850 cm − 1 are related to the asymmetric and symmetric stretching vibrations of the C-H bond in the CH 2 group, the bands at 1600, 1500, 1450 and 1420 cm − 1 are characteristic of vibrations in the aromatic ring, the band at 1260 cm − 1 is related to the asymmetric stretching vibrations of = C-O-C in the aromatic ether group, or to the deformation vibrations of C-H, the bands at 1150 and 1070 cm − 1 correspond to the asymmetric stretching vibrations of -C-O in the aliphatic ether group. The presence of the listed functional groups indicates that the material under study contains not only organized carbon structures in the form of graphene layers, but also compounds of amorphous carbon and by-products of electric arc synthesis of carbon materials. In the case of oxidized astralenes, bands characteristic of symmetric and asymmetric stretching vibrations of C-H bonds in the CH 2 and CH 3 groups are observed at 2960, 2920 and 2850 cm − 1 . Also, unlike the initial astralenes, a band at 1705 cm − 1 appears in the spectrum of oxidized astralenes, characteristic of stretching vibrations of C = O of the carbonyl group, a number of bands in the range of 1580 − 1500 cm − 1 and a band at 1400 cm − 1 , characteristic of vibrations of aromatic rings. The band at 1270 cm − 1 in the spectrum of oxidized astralenes may indicate the presence of Ar-N stretching vibrations in disubstituted aromatic amine, which may be the result of interaction of a part of diisopropylethylamine with astralenes. The bands at 1170 and 1110 cm − 1 indicate the presence of C-O bond vibrations in ethers and esters. In the case of modified astralene, intense bands at 2963 and 2924 cm − 1 are characteristic of asymmetric stretching vibrations of the C-H bond in the -CH 3 and CH 2 groups, and the band at 2850 cm − 1 is due to ν s vibrations of the C-H bond in the CH 2 group, and the ratio of the bands at 2963 and 2924 cm − 1 shows that the number of CH 3 groups is much greater in the modified astralene sample compared to the initial and oxidized samples. Also, intense absorption bands of ester groups are observed: 1740 cm − 1 , characteristic of the stretching vibrations of the C = O bond in the ester group, 1180 cm − 1 ν s C-O-C in the ester group, 1095 and 1027 cm − 1 ν as C-O-C of the ester group. Also, vibrations in simple ester groups can contribute to the enhancement of the bands at 1180, 1095 and 1027 cm − 1 . Bands at 1603, 1581, 1458 and 1412 cm − 1 are observed, characteristic of vibrations in the aromatic ring. A band at 1260 cm − 1 of the stretching vibrations of C-N in the trisubstituted amino group included in the composition of procaine is observed. There are also two amide bands of 669 cm − 1 of N-H deformation vibrations in the amide group and 1510 cm − 1 of N-H bond deformation vibrations in secondary amides. The appearance of these bands can be explained by the fact that the interaction of the diazonium salt and astralenes can proceed by the azo coupling mechanism, in which the decomposition of two nitrogen atoms to form a gas molecule does not occur, but the formation of the R-N = N-R' structure does [ 14 ]. In addition, a high-intensity band of 800 cm − 1 is observed in the spectrum, characteristic of vibrations of the para-substituted aromatic ring. It is worth noting that the original procaine used to obtain the modifying agent, although it has a para-substituted aromatic ring, does not give a characteristic signal in the "fingerprint" region. A change in the nature of vibrations in this region indicates the addition of another substituent to the aromatic ring included in the procaine. This fact, together with the appearance in the spectrum of modified astralenes of intense bands characteristic of functional groups included in the composition of procaine, indicates that a covalent bond is formed between the carbon particles and the organic component, that is, the modification of the surface of the astralenes was achieved successfully. Next, to confirm the modification of astralenes, the thermal stability of the original, oxidized and modified astralenes was assessed and compared (Fig. 5 ). It is evident from Fig. 5 that the destruction of astralene samples is a multi-stage process. Thus, the initial sample is characterized by the presence of several minor destruction stages up to 300 ℃, which can be attributed to the desorption of various impurities. Further, for this sample, a number of destruction processes are observed at temperatures of about 385, 480, 540 and 575 ℃ with a sample mass loss of 0.95, 0.33, 0.27 and 0.25%, respectively, which can be attributed to the destruction of disordered carbon in the sample [ 15 , 16 ]. With increase in temperature, the following destruction processes are observed: steps at temperatures of 636, 679, 753 and 770 ℃ with mass losses of 0.6, 0.51, 1.13 and 0.36%, respectively. High-temperature destruction steps are characterized by a greater mass loss, which can probably be attributed to the destruction of defective graphene layers [ 16 , 17 ]. The destruction step at 850 ℃ with a mass loss of 4.84% is explained by many authors as the destruction of graphene layers [ 16 , 17 , 18 ]. In the case of oxidized astralenes, as expected, the presence of oxygen-containing groups in the structure leads to more pronounced destruction, which is evident from the DTG curve. Thus, the thermogravimetric curve for oxidized astralenes is characterized by a loss of 1.04% of the mass upon heating to 103℃, which is typical for the evaporation of moisture from the sample. The steps at temperatures of 156, 248, and 328℃ with mass losses of 0.31, 0.32, and 1.53%, respectively, can be attributed to the destruction of oxygen-containing groups on the surface of the particles [ 19 ]. The destruction step with a mass loss of 3.4% observed at a temperature of 464℃ is typical for the decomposition of disordered carbon in the material [ 15 , 16 ]. The destruction of the graphene surface layer in the oxidized astralenes can explain a fairly large destruction step at a temperature of 689℃ with a mass loss of 4.89% [ 16 , 17 ]. When comparing this step in the oxidized astralenes with the original sample, it is clear that the mass loss is almost twice as high, even in the case of summing up the mass losses of the original sample at temperatures of 636, 679, 753 and 770 ℃. This result of the oxidized astralenes correlates with the fact that, as a result of the decomposition of oxygen-containing groups at lower temperatures, the graphene surface sheet contains a large number of defects, the presence of which facilitates its further destruction. As for the original astralene sample, the destruction step at a temperature of 796℃ with a mass loss of 6.62% for the oxidized astralenes can be associated with the destruction of the graphene layers [ 16 – 18 ]. Modified astralenes, like oxidized ones, are characterized by the presence of a greater number of mass loss stages, compared to the original particles. The first mass loss stage (the stage at 82℃ with a mass loss of 0.88%) is associated with the loss of adsorbed moisture on the sample. The second (121℃, 0.69%) and third (242℃, 0.75%) mass loss stages can be attributed to the destruction of oxygen-containing areas on the surface of modified astralenes [ 19 ]. At temperatures of 312 and 457℃ (mass losses of 2.68 and 2.47%, respectively), the destruction of organic structures on the particle surface occurs, since these temperatures are characteristic of procaine destruction. The destruction of graphene layers (at a temperature of 802℃) for modified astralenes is more pronounced than the destruction of the surface layer of graphene (693℃), unlike oxidized astralenes, probably due to greater surface modification. As can be seen from the comparison of the TG analysis results, both stages of particle modification affect the outer graphene layer, somewhat reducing its thermal stability. The influence of modified astralenes on the polymerization process The effect of modified astralenes on the polymerization process was assessed using FTIR spectroscopy. For this purpose, the prepared monomer mixture was placed on the crystal of the NTR attachment, covered with a polyethylene terephthalate film to limit the contact of the reaction mass with atmospheric oxygen, and irradiated with a laser in the mode: λ = 532 nm, I = 200 µW/cm 2 , for 750 sec. In parallel with laser irradiation, FTIR spectra were recorded every 7.5 seconds, in which the intensity of the band at 1640 cm − 1 , characteristic of vibrations of C = C bonds in monomer molecules, was monitored. Based on the change in the maximum intensity of this band over time, the kinetics of the polymerization process was calculated (Fig. 6 ). Figure 6 shows the experimental curves of photopolymerization processes. It is evident that with an increase in the concentration of particles in the reaction mass, the rate of the process of opening C = C bonds decreases, but the changes are not significant, and the observed values ​​of monomer conversion are comparable. The effect of additives of modified astralenes on the maximum rate of the polymerization process was also investigated (Fig. 7 ). From Fig. 7 A it is seen that the undoped monomer mixture has the highest monomer conversion rate of 4.55%/sec, with an increase in the concentration of astralenes the maximum value decreases to 2.27, 1.98, 1.31%/sec, respectively. The observed slowdown in the polymerization process can be explained by a number of reasons. The authors of [ 20 – 23 ] observed similar results of a decrease in the polymerization rate, as well as a decrease in the degree of conversion with an increase in the proportion of carbon particles in the system. As described by the authors, compositions with a high filler content suffer from side effects associated with increased viscosity and a decrease in photocuring conversion. In [ 24 ], the optimal concentration of CNTs in a commercial photocurable resin was found to be up to 0.3 wt.%, above which the compositions lose good rapid polymerization capabilities, which is necessary for printing on a DLP printer. The authors of [ 25 , 26 ] observed inhibition of free radical polymerization while introducing C 60 fullerene and carbon nanotubes into the monomer mixture. As the authors describe, the reason for the inhibition is the formation of stable radicals with lower chemical activity as a result of the interaction of free radicals with carbon particles, which, due to the presence of a system of conjugated bonds, are capable of effectively delocalizing unpaired electrons of radicals. Since the polymerization process is initiated by radiation, the effect of fillers on the optical properties of the reaction mass is of no small importance. The authors of [ 27 ] showed that polymerization of a mixture with fillers slows down as a result of a decrease in the radiation intensity across the thickness due to light scattering. Especially in cases where the refractive index of the filler differs greatly from the refractive index of the monomers. Also, from Fig. 7 A it is evident that when astralenes are added, the maximum polymerization rate is practically not shifted, but remains at a conversion value of ~ 40%. At the same time, due to the decrease in the polymerization rate, the maximum rate shifts in time, and is 25, 53, 59 and 60 sec (Fig. 7 B). For a more detailed analysis of the influence of astralenes on the polymerization rate, the Sestak-Berggren equation was used [ 28 , 29 ]. To simplify the calculations, the beginning of the polymerization process was considered - the section in which the conversion of monomers over time has a linear character (from 0 to 70 sec). Thus, it is possible to obtain a simplified autocatalytic kinetic model, from which it is possible to obtain the rate constant of the polymerization process (Table 1 ). Table 1 Effect of modified astralenes on the polymerization process Content of astralenes, % wt. Monomer conversion, % Polymerization rate, %/sec Polymerization rate constant 0.00 96.06 4.55 4.46719*10 − 2 0.01 94.06 2.27 3.09309*10 − 2 0.05 94.36 1.98 2.91599*10 − 2 0.10 91.52 1.31 2.10068*10 − 2 It is evident that the introduction of modified astralenes reduces the polymerization rate constant at the initial stage of the process by more than 40% on average. The obtained result is consistent with the results and assumptions given above. Properties of the polymer composite As a result, polymer composite films were obtained by photopolymerization of a mixture of acrylates with modified astralenes. The thickness of the studied samples was 20 µm. Figure 8 shows the optical transmission of the obtained films. It can be seen that all samples are characterized by a comparable transmittance value of ~ 90% in the visible spectrum and NIR range (500–1100 nm). Based on the obtained UV spectra, the optical band gap was calculated using the Tautz method (Table 2 ). Table 2 Optical band gap values ​​of composites Sample Band gap width, eV Polymer 3.93 Polymer + Astr_0.01% 3.90 Polymer + Astr_0.05% 3.90 Polymer + Astr_0.10% 3.89 It is evident that the introduction of such small additions of astralenes does not lead to a significant change in the band gap. The value characteristic of dielectric materials is retained. Conclusions During the research, a successful modification of astralenes was achieved, leading to a decrease in the content of disordered carbon in the composition of the samples, as well as modification of the particle surface with various functional groups, which is confirmed by Raman and FTIR spectroscopy, TG analysis. At the same time, the toroidal structure of the particles is preserved, which is confirmed by TEM. It has been established that the modified particles are compatible with acrylic monomers and can be used to obtain composite polymer materials by photopolymerization filling. At the same time, the introduction of astralenes decreases the polymerization rate. At the initial stage of photopolymerization, a slowdown of more than 40% is observed. However, the degree of monomer conversion for acrylates with astralenes is comparable to the results obtained during polymerization of compositions without astralenes. All the obtained samples are characterized by similar transmission indices in the visible spectrum and NIR range, which indicates a uniform distribution of particles in the matrix volume. The optical band gap changes insignificantly when introducing astralene particles, the materials remain a dielectric. Declarations Conflict of interest The authors declare that they do not have any commercial or associative interest that Author Contribution V.T. and J.B. participated in conceptualization of the article. V.T., J.B. and V.S. wrote the main text of the article. V.T. and A.I. developed the particle modification methodology. S.K. was involved in the transmission electron microscopy section. V.S. was involved in the FTIR spectroscopy and thermogravimetric analysis section. V.T., J.B., and V.S. were involved in studying the polymerization kinetics. V.T., J.B., and A.I. were involved in studying the optical properties of the composite. All five authors made revisions and approved the final text of the article. Acknowledgement The authors express their gratitude to the head of the laboratory of the Information Optical Technologies Center of ITMO University, Kirill Bogdanov, for measurements on the Raman spectrometer. 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Sci Rep 9:5224. https://doi.org/10.1038/s41598-019-41563-w Li H, Zhang et al (2002) J Phys : Condens Matter 14:1697 Amit Mahajan A, Kingon Z, Konya PM, Vilarinho (2013) Studies on the thermal decomposition of multiwall carbon nanotubes under different atmospheres, Materials Letters, Volume 90, Pages 165–168, ISSN 0167-577X, https://doi.org/10.1016/j.matlet.2012.08.120 Fu Liu M, Wang Y, Chen J, Gao (2019) Thermal stability of graphene in inert atmosphere at high temperature. J Solid State Chem 276 Pages 100–103, ISSN 0022-4596. https://doi.org/10.1016/j.jssc.2019.04.008 Giang TT, Le J, Manyam P, Opaprakasit N, Chanlek N, Grisdanurak P, Sreearunothai (2018) Divergent mechanisms for thermal reduction of graphene oxide and their highly different ion affinities. Diam Relat Mater 89:246–256. https://doi.org/10.1016/j.diamond.2018.09.006 Li Chen L, Yanling Y, Jun Y, Weibo Z, Ran, Du Shiguo and Niu Ke (2021) Effect of long-term ageing on graphene oxide: structure and thermal decomposition. R Soc Open Sci 8:202309. http://doi.org/10.1098/rsos.202309 Capek I, Kocsisová T (2011) On the preparation of composite poly(butyl acrylate)/carbon nanotube nanoparticles by miniemulsion polymerization of butyl acrylate. Polym J 43:700–707. https://doi.org/10.1038/pj.2011.50 Wiktoria Tomal D, Krok A, Chachaj-Brekiesz J, Ortyl Beneficial stilbene-based derivatives: From the synthesis of new catalytic photosensitizer to 3D printouts and fiber-reinforced composites. Eur Polymer J, 156, 2021, 110603, ISSN 0014-3057, https://doi.org/10.1016/j.eurpolymj.2021.110603 Wiktoria Tomal D, Krok A, Chachaj-Brekiesz P, Lepcio J, Ortyl B (2021) 102447, ISSN 2214–8604, https://doi.org/10.1016/j.addma.2021.102447 Gustavo Gonzalez A, Chiappone I, Roppolo E, Fantino V, Bertana F, Perrucci L, Scaltrito F, Pirri M, Sangermano (2017) Development of 3D printable formulations containing CNT with enhanced electrical properties. Polymer 109 Pages 246–253, ISSN 0032-3861. https://doi.org/10.1016/j.polymer.2016.12.051 Quanyi Mu L, Wang CK, Dunn X, Kuang F, Duan Z, Zhang HJ, Qi T, Wang (2017) Digital light processing 3D printing of conductive complex structures, Additive Manufacturing, Volume 18, Pages 74–83, ISSN 2214–8604, https://doi.org/10.1016/j.addma.2017.08.011 Pabin–Szafko B, Wiśniewska E, Szafko J (2006) Carbon nanotubes and fullerene in the solution polymerisation of acrylonitrile. Eur Polymer J 42(7) Pages 1516–1520, ISSN 0014-3057. https://doi.org/10.1016/j.eurpolymj.2006.01.008 Seno M, Maeda M, Sato T (2000) Effect of fullerene on radical polymerization of vinyl acetate. J Polym Sci Polym Chem 38:2572–2578. https://doi.org/10.1002/1099-0518(20000715)38:143.0.CO;2-3 Badev A, Abouliatim Y, Chartier T, Lecamp L, Lebaudy P, Chaput C, Delage C Photopolymerization kinetics of a polyether acrylate in the presence of ceramic fillers used in stereolithography, Journal of Photochemistry and Photobiology A: Chemistry, 222, Issue 1, 2011, Pages 117–122, ISSN 1010–6030, https://doi.org/10.1016/j.jphotochem.2011.05.010 Rwei S, Chen Y-M, Chiang W-Y, Ting Y-T (2017) A Study of the Curing and Flammability Properties of Bisphenol A Epoxy Diacrylate Resin Utilizing a Novel Flame Retardant Monomer, bis[di-acryloyloxyethyl]-p-tert-butyl-phenyl Phosphate. Materials 10:202. 10.3390/ma10020202 Xing WY, Hu Y, Song L, Xilei C, Zhang, Ping, Ni J (2009) Thermal degradation and combustion of a novel UV curable coating containing phosphorus. Polym Degrad Stab 94:1176–1182. 10.1016/j.polymdegradstab.2009.02.014 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 01 Mar, 2025 Read the published version in Polymer Bulletin → Version 1 posted Editorial decision: Revision requested 02 Jan, 2025 Reviews received at journal 12 Dec, 2024 Reviewers agreed at journal 12 Dec, 2024 Reviewers invited by journal 16 Sep, 2024 Editor assigned by journal 09 Aug, 2024 Submission checks completed at journal 07 Aug, 2024 First submitted to journal 06 Aug, 2024 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4866698","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":341398035,"identity":"2929cd4d-558e-4285-9176-e3102bde80e2","order_by":0,"name":"Valentine E. Tarasov","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAu0lEQVRIiWNgGAWjYFAD9sYGYpUyQ2meg0TrgWmRSGAkTovB8f6Dnytq6uQMbj5uf3SjgiHf4AAhLWcOM0ueOXbY2OB2YmNzzhkGyw2EtEjOSGaQbGA7kDhzNlBLbhuDAUFbJOc/Zv7Z8K8ucebMg0Rq4ZdgZpNsbGNO7JdgJFYLT7KZZWPfYWN+nsTG2TlnJAwkCWlhYz/4+GbDtzo5NvbjDz7nVNgY8BHSgg4kSFQ/CkbBKBgFowArAABakD+lW70BewAAAABJRU5ErkJggg==","orcid":"","institution":"ITMO University","correspondingAuthor":true,"prefix":"","firstName":"Valentine","middleName":"E.","lastName":"Tarasov","suffix":""},{"id":341398036,"identity":"4734d18d-e1c9-4787-8d3c-0843911d8caf","order_by":1,"name":"Julia A. Burunkova","email":"","orcid":"","institution":"ITMO University","correspondingAuthor":false,"prefix":"","firstName":"Julia","middleName":"A.","lastName":"Burunkova","suffix":""},{"id":341398037,"identity":"276fa044-6b6e-460e-b260-f523dbf7385e","order_by":2,"name":"Vera E. Sitnikova","email":"","orcid":"","institution":"ITMO University","correspondingAuthor":false,"prefix":"","firstName":"Vera","middleName":"E.","lastName":"Sitnikova","suffix":""},{"id":341398038,"identity":"32f08151-6127-46d4-9da4-ade6baffe05a","order_by":3,"name":"Sergey A. Karpov","email":"","orcid":"","institution":"St Petersburg State University","correspondingAuthor":false,"prefix":"","firstName":"Sergey","middleName":"A.","lastName":"Karpov","suffix":""},{"id":341398039,"identity":"11f75f91-021f-422b-9a0f-e4d48c059813","order_by":4,"name":"Aleksey V. Ivanov","email":"","orcid":"","institution":"Petersburg University of State Fire Service of Emercom of Russia","correspondingAuthor":false,"prefix":"","firstName":"Aleksey","middleName":"V.","lastName":"Ivanov","suffix":""}],"badges":[],"createdAt":"2024-08-06 08:09:42","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4866698/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4866698/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00289-025-05684-9","type":"published","date":"2025-03-01T15:57:38+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":64025646,"identity":"40f98cd1-551b-43a1-a7c5-f17311e535d3","added_by":"auto","created_at":"2024-09-05 07:40:29","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":8031,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the astralenes modification process with diazonium salt\u003c/p\u003e","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/0e4cd182c2d903ada6896206.jpg"},{"id":64026082,"identity":"313ad302-7fd2-469e-979a-62f2b405e96b","added_by":"auto","created_at":"2024-09-05 07:48:29","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":18950,"visible":true,"origin":"","legend":"\u003cp\u003eTEM images of astralenes, where A – initial particles, B – modified particles\u003c/p\u003e","description":"","filename":"Fig.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/43936dedc292a9671e7433c0.jpg"},{"id":64026080,"identity":"e84b194b-c6d2-4f78-bab4-64c46024af19","added_by":"auto","created_at":"2024-09-05 07:48:29","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":32955,"visible":true,"origin":"","legend":"\u003cp\u003eRaman spectra of the initial and oxidized astralenes\u003c/p\u003e","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/92076945f9d5e0f7ce399b26.jpg"},{"id":64026085,"identity":"42ca1939-4b99-4721-b3c4-111764dffaf9","added_by":"auto","created_at":"2024-09-05 07:48:30","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":31554,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR transmission spectra of astralenes\u003c/p\u003e","description":"","filename":"Fig.4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/70eb6e20c71a04b6555b32bb.jpg"},{"id":64026081,"identity":"2485d087-daa8-482a-83fc-1de5eb13337f","added_by":"auto","created_at":"2024-09-05 07:48:29","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":25353,"visible":true,"origin":"","legend":"\u003cp\u003eThermogravimetric analysis of astralenes, where A – TG curves, B – DTG curves\u003c/p\u003e","description":"","filename":"Fig.5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/2e5c29e990cf45321d4d343a.jpg"},{"id":64026815,"identity":"91482fd5-b37b-4c2a-860b-f89840b13240","added_by":"auto","created_at":"2024-09-05 07:56:29","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":34766,"visible":true,"origin":"","legend":"\u003cp\u003eKinetics of polymerization of the studied samples\u003c/p\u003e","description":"","filename":"Fig.6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/998717ae486a01df0f29268b.jpg"},{"id":64025649,"identity":"50b328e6-2c9d-42b1-bf36-3331175cdaa5","added_by":"auto","created_at":"2024-09-05 07:40:29","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":30384,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of modified astralenes on the polymerization rate\u003c/p\u003e","description":"","filename":"Fig.7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/55a38cc7c47717f3fba73e7e.jpg"},{"id":64025653,"identity":"20c6f445-3295-4f5c-af1a-60eb4022cb3e","added_by":"auto","created_at":"2024-09-05 07:40:29","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":34532,"visible":true,"origin":"","legend":"\u003cp\u003eTransmission of polymer films filled with astralenes\u003c/p\u003e","description":"","filename":"Fig.8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/28fdca58c29050ed234754c8.jpg"},{"id":77622493,"identity":"783c2d7c-2fe2-4a40-acaf-da809ad0baaa","added_by":"auto","created_at":"2025-03-03 16:07:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":969173,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4866698/v1/4c3fb675-e4a9-4a17-8a4a-28308b371b7a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Surface modification of astralenes for obtaining optical composites based on photocurable acrylates","fulltext":[{"header":"Introduction","content":"\u003cp\u003eComposite materials, including polymer optical nanocomposites, are becoming increasingly widespread. Their distribution is due to two advantageous features: the ability to impart a wide range of properties to the polymer matrix by doping it with a number of functional additives, as well as the ability to create flexible films and complex-shaped coatings. Among polymers, acrylates are the most suitable for producing optical elements due to their transparency in the visible range, chemical stability, and resistance to UV radiation. Some acrylates are also capable of photo-initiated polymerization, which allows creating photonic structures [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. One of the disadvantages of optical polymer materials is their lower thermal stability and strength characteristics compared to classic inorganic glasses. The solution to this problem is to modify the polymer matrix with structuring fillers, such as carbon nanoparticles.\u003c/p\u003e \u003cp\u003eAmong the wide range of carbon structures, a relatively little-studied form, astralenes, is of interest. Astralenes are carbon multilayer nanostructures of toroidal shape obtained by the electric arc method, individual layers of which are formed by a combination of penta- and hexagonal cycles, the average size varies from 15 to 100 nm [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. These structures have an anisotropic shape, high surface energy, when an electric field is applied, they are capable of polarizing with the formation of dipoles [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The ability of astralenes to be a structural modifier of various media, a modifier of electrical conductivity, mechanical properties, and thermal stability of materials based on epoxy resins, to act as microcrack stoppers and a reducer of moisture absorption in materials has been proven [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Moreover, the semiconductor and nonlinear optical properties for this form of carbon are known [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], This determines the interest in studying optical composites based on them.\u003c/p\u003e \u003cp\u003eIt is worth noting that the efficiency of using astralenes, like other carbon nanoparticles, as modifying agents is limited by their fairly high tendency to agglomerate, leading to uneven distribution in the polymer volume [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The classic way to solve this problem is particles surface modification. It is known that surface modification can be carried out by introducing a surfactant or by chemically attaching structural groups to the surface of the astralene. However, a shell of chemically grafted groups is usually more resistant to physical and chemical influences, so it is more preferable for our research.\u003c/p\u003e \u003cp\u003eNonetheless, in some cases, the grafting of oxygen-containing groups may be insufficient to effectively prevent particle aggregation. The affinity of particles to the medium can be increased by attaching organic chains with a complex structure to the locations of oxygen-containing functional groups. For example, work [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] shows the possibility of modifying graphene oxide by reacting its particles with ethylenediamine in a 2-butanol solution with heating and stirring. As a result of the reaction, chains containing a terminal amino group are attached to the surface of graphene oxide particles. Work [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] describes a number of methods for modifying the surface of astralenes: oxidative treatment, [3\u0026thinsp;+\u0026thinsp;2] cycloaddition according to the Prato reaction, reaction with diazonium salts, reaction with hydrazine. Based on the above, for effective modification of particles, our research group selected a technique consisting of an oxidative stage and a subsequent stage of treating the particles with a diazonium salt.\u003c/p\u003e \u003cp\u003eIt is worth noting that modification of the astralene surface, in addition to reducing coagulation, can provide some compensation for the disruption of the conjugated bond system in places of structural defects. Since astralene particles consist of folded graphene sheets, like carbon nanotubes, these layers are characterized by a system of conjugated bonds that provide many unique properties of these particles. Unfortunately, defects in the structure lead to a decrease in the quality of the conjugated system. Therefore, the authors suggested that it is preferable to attach substituents to the astralene surface, which, due to the peculiarities of their structure, have the ability to be integrated into the system of conjugated bonds of the astralene.\u003c/p\u003e \u003cp\u003eThus, the goal of this study is to obtain surface modified astralenes compatible with photocurable acrylic monomers to create an optical polymer medium.\u003c/p\u003e"},{"header":"Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMaterials\u003c/h2\u003e \u003cp\u003eIn the course of the study, carbon nanoparticles \u0026ndash; astralenes [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] were used. For their modification, the following were used: sulfuric acid 92% (CAS#:7664-93-9), potassium permanganate (CAS#:7722-64-7), diisopropylethylamine (CAS#:7087-68-5), methylene chloride (CAS#:75-09-2), procaine hydrochloride (CAS#:51-05-8), sodium nitrite (CAS#:7632-00-0), hydrochloric acid 36% (CAS#: 7647-01-0), ethyl alcohol (CAS#:64-17-5), distilled water.\u003c/p\u003e \u003cp\u003eThe following monomers were used to create the polymer matrix: ethylene glycol phenyl ether acrylate (2-phenoxyethyl acrylate) (CAS#:48145-04-6), bisphenol A glycerate (CAS#:4687-94-9), 2-carboxyethyl acrylate (CAS#:24615-84-7), in the ratio: 6:3:1. The photoinitiator bis(cyclopentadienyl)bis[2,6-difluoro-3-(1-pyrryl)phenyl] titanium (Irgacure 784) (CAS No. 125051-32-3) was used as a source of free radicals.\u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003eModification of astralenes\u003c/h2\u003e \u003cp\u003eOxidative modification of astralenes (Astr) was carried out under conditions of interphase catalytic oxidation [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Methylene chloride was used as the organic phase, and a saturated solution of potassium permanganate in an aqueous solution of sulfuric acid (pH\u0026thinsp;=\u0026thinsp;1) was used as the aqueous phase. Diisopropylethylamine was used as a catalyst. Oxidation of carbon particles was carried out in a round-bottomed flask with a reflux condenser, at the boiling point of the organic solvent, for 1 hour. After that, the remaining permanganate was decomposed with sodium nitrite, and methylene chloride was distilled from the flask. Then the particles were washed to a neutral wash and dried at 105 ℃.\u003c/p\u003e \u003cp\u003eFurther modification was performed by interaction of oxidized astralene particles (Astr_Ox) with diazonium salt obtained from procaine hydrochloride. For this purpose, oxidized astralenes were introduced into the reaction mass before the synthesis. The synthesis of diazonium salt was executed in a classical way: by portionwise addition of sodium nitrite solution into acidified procaine solution while stirring in a beaker. In this case, the process temperature should not exceed 5℃, and the acidity of the medium should be pH\u0026thinsp;~\u0026thinsp;1, to avoid decomposition of diazonium salt and formation of by-products of organic synthesis. After completion of the diazotization reaction, the beaker was subjected to ultrasonic treatment (~\u0026thinsp;10 minutes, frequency 35 kHz, power 55 W) until the release of gas bubbles \u0026ndash; nitrogen, which is a decomposition product of diazonium salt, ceased. The modification process scheme is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAfter ultrasonic treatment, the particles were precipitated by centrifugation, washed to neutral wash and dried at a temperature of 105 ℃.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eTransmission electron microscopy of astralenes\u003c/h2\u003e \u003cp\u003eSuspended in 70% ethanol astralene particles were placed on copper slot grids covered with pioloform film, dried, and observed on the transmission electron microscope JEM 1400 (Jeol company) at accelerating voltage of 80 kV.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eRaman spectroscopy of astralenes\u003c/h2\u003e \u003cp\u003eThe structure of astralenes before and after modification was studied using a Renishaw \u0026lsquo;inVia\u0026rsquo; micro-Raman spectrometer in the range 4000\u0026ndash;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with a laser wavelength of 488 nm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eFTIR spectroscopy of astralenes\u003c/h2\u003e \u003cp\u003eThe FTIR spectra of the samples were recorded using a Bruker Tensor 37 FTIR spectrometer. The FTIR transmission spectra of astralene particles were obtained using a standard potassium bromide pellet preparation technique in the 4000\u0026ndash;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range with a resolution of 2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and averaging over 32 scans.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStudy of astralenes influence on polymerization\u003c/h2\u003e \u003cp\u003eThe effect of the modified astralene particles on the photopolymerization of acrylates was studied by FTIR spectroscopy using a Pike MIRacle ATR attachment with a diamond-coated zinc selenide crystal in the 4000\u0026ndash;600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range, a spectral resolution of 2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and averaging over 5 scans. These instrument settings allowed recording a series of measurements with a time resolution of 7.5 seconds between spectra.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStudy of astralenes thermal destruction\u003c/h2\u003e \u003cp\u003eThermal properties of the initial and modified astralenes were studied using a NETZSCH TG 209 F1 Libra thermogravimetric analyzer in the range of 25\u0026ndash;900\u0026deg;C at a heating rate of 3\u0026deg;C/min in a nitrogen environment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003ePreparation of polymer composite\u003c/h2\u003e \u003cp\u003eParticles of modified astralene were used to create an optical composite based on acrylates. For this purpose, a suspension of modified astralenes in ethanol was obtained by ultrasonic treatment (treatment time: 10 minutes, frequency 35 kHz, power 55 W). After that, the suspension was introduced into a mixture of bisphenol A glycerate and 2-carboxyethyl acrylate. The samples were heated to 50 ℃ with stirring until the ethanol was completely removed, then ethylene glycol phenyl ether acrylate was added. After the photoinitiator Irgacure 784 was introduced into the mixture in an amount of 0.5% of the monomer mass. The content of astralenes in the mixtures varied and amounted to 0.01, 0.05 and 0.10%wt. of the monomer mass.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eMeasurement of polymer composites transparency\u003c/h2\u003e \u003cp\u003eThe influence of astralene particles on the transparency of the polymer material was assessed using a Unico UV spectrometer (USA) in the range of 190\u0026ndash;1100 nm with a resolution of 1 nm.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eResearch of modified astralenes\u003c/h2\u003e \u003cp\u003eAfter modification, the initial and surface-modified particles (Astr_Mod) of astralenes were examined by transmission electron microscopy. The obtained images of the astralene particles are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA, the original astralenes are toroidal structures demonstrating a high tendency to agglomeration. The size of individual particles varies in the range from 20 to 90 nm. From the image of modified astralenes (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), it is evident that after modification, the particles are not destroyed and retain a toroidal shape, the sizes of individual particles are in the same range as the sizes of the original ones.\u003c/p\u003e \u003cp\u003eThe initial and oxidized astralenes were studied by Raman spectroscopy to assess the efficiency of the oxidative modification stage. The obtained spectra are presented below (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThree peaks are clearly visible in the spectra of the initial and oxidized astralenes: 2710 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1580 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1355 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, known as 2D, G and D bands. From Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e it is evident that after the oxidative treatment, the intensity of the D band (1355 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), related to the vibration of the edge and defective areas in the structure, i.e. disordered carbon, decreases, and an increase in the intensity of the G band (1580 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), related to the vibration of bonds in the graphene sheet, is also observed. The ratio of the D and G bands changes from 0.4758 for the initial particles to 0.2980 for the oxidized particles. This result, as expected, indicates a decrease in the content of disordered carbon from the sample composition. Also, in both samples, an intense 2D band (2710 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) is observed, indicating that the studied particles consist of several graphene layers [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. It should be noted that the Raman spectroscopy method at an excitation wavelength of λ\u0026thinsp;=\u0026thinsp;488 nm is not applicable for studying modified astralenes, since the presence of organic groups on the surface of the particles causes them to luminesce.\u003c/p\u003e \u003cp\u003eThe initial, oxidized and modified astralenes were studied using FTIR spectroscopy (in transmission mode), for which potassium bromide-based tablets of samples were prepared (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), which made it possible to evaluate the effectiveness of the modification process.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFrom Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e it is evident that the initial astralenes are characterized by the presence of a band at 2960 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is related to the asymmetric stretching vibrations of the C-H bond in the -CH\u003csub\u003e3\u003c/sub\u003e group, the bands at 2920 and 2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are related to the asymmetric and symmetric stretching vibrations of the C-H bond in the CH\u003csub\u003e2\u003c/sub\u003e group, the bands at 1600, 1500, 1450 and 1420 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are characteristic of vibrations in the aromatic ring, the band at 1260 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is related to the asymmetric stretching vibrations of =\u0026thinsp;C-O-C in the aromatic ether group, or to the deformation vibrations of C-H, the bands at 1150 and 1070 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to the asymmetric stretching vibrations of -C-O in the aliphatic ether group. The presence of the listed functional groups indicates that the material under study contains not only organized carbon structures in the form of graphene layers, but also compounds of amorphous carbon and by-products of electric arc synthesis of carbon materials.\u003c/p\u003e \u003cp\u003eIn the case of oxidized astralenes, bands characteristic of symmetric and asymmetric stretching vibrations of C-H bonds in the CH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e groups are observed at 2960, 2920 and 2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Also, unlike the initial astralenes, a band at 1705 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appears in the spectrum of oxidized astralenes, characteristic of stretching vibrations of C\u0026thinsp;=\u0026thinsp;O of the carbonyl group, a number of bands in the range of 1580\u0026thinsp;\u0026minus;\u0026thinsp;1500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a band at 1400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, characteristic of vibrations of aromatic rings. The band at 1270 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the spectrum of oxidized astralenes may indicate the presence of Ar-N stretching vibrations in disubstituted aromatic amine, which may be the result of interaction of a part of diisopropylethylamine with astralenes. The bands at 1170 and 1110 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e indicate the presence of C-O bond vibrations in ethers and esters.\u003c/p\u003e \u003cp\u003eIn the case of modified astralene, intense bands at 2963 and 2924 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are characteristic of asymmetric stretching vibrations of the C-H bond in the -CH\u003csub\u003e3\u003c/sub\u003e and CH\u003csub\u003e2\u003c/sub\u003e groups, and the band at 2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is due to ν\u003csub\u003es\u003c/sub\u003e vibrations of the C-H bond in the CH\u003csub\u003e2\u003c/sub\u003e group, and the ratio of the bands at 2963 and 2924 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e shows that the number of CH\u003csub\u003e3\u003c/sub\u003e groups is much greater in the modified astralene sample compared to the initial and oxidized samples. Also, intense absorption bands of ester groups are observed: 1740 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, characteristic of the stretching vibrations of the C\u0026thinsp;=\u0026thinsp;O bond in the ester group, 1180 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ν\u003csub\u003es\u003c/sub\u003e C-O-C in the ester group, 1095 and 1027 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ν\u003csub\u003eas\u003c/sub\u003e C-O-C of the ester group. Also, vibrations in simple ester groups can contribute to the enhancement of the bands at 1180, 1095 and 1027 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Bands at 1603, 1581, 1458 and 1412 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are observed, characteristic of vibrations in the aromatic ring. A band at 1260 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of the stretching vibrations of C-N in the trisubstituted amino group included in the composition of procaine is observed. There are also two amide bands of 669 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of N-H deformation vibrations in the amide group and 1510 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of N-H bond deformation vibrations in secondary amides. The appearance of these bands can be explained by the fact that the interaction of the diazonium salt and astralenes can proceed by the azo coupling mechanism, in which the decomposition of two nitrogen atoms to form a gas molecule does not occur, but the formation of the R-N\u0026thinsp;=\u0026thinsp;N-R' structure does [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In addition, a high-intensity band of 800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is observed in the spectrum, characteristic of vibrations of the para-substituted aromatic ring. It is worth noting that the original procaine used to obtain the modifying agent, although it has a para-substituted aromatic ring, does not give a characteristic signal in the \"fingerprint\" region. A change in the nature of vibrations in this region indicates the addition of another substituent to the aromatic ring included in the procaine. This fact, together with the appearance in the spectrum of modified astralenes of intense bands characteristic of functional groups included in the composition of procaine, indicates that a covalent bond is formed between the carbon particles and the organic component, that is, the modification of the surface of the astralenes was achieved successfully.\u003c/p\u003e \u003cp\u003eNext, to confirm the modification of astralenes, the thermal stability of the original, oxidized and modified astralenes was assessed and compared (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIt is evident from Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e that the destruction of astralene samples is a multi-stage process. Thus, the initial sample is characterized by the presence of several minor destruction stages up to 300 ℃, which can be attributed to the desorption of various impurities. Further, for this sample, a number of destruction processes are observed at temperatures of about 385, 480, 540 and 575 ℃ with a sample mass loss of 0.95, 0.33, 0.27 and 0.25%, respectively, which can be attributed to the destruction of disordered carbon in the sample [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. With increase in temperature, the following destruction processes are observed: steps at temperatures of 636, 679, 753 and 770 ℃ with mass losses of 0.6, 0.51, 1.13 and 0.36%, respectively. High-temperature destruction steps are characterized by a greater mass loss, which can probably be attributed to the destruction of defective graphene layers [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The destruction step at 850 ℃ with a mass loss of 4.84% is explained by many authors as the destruction of graphene layers [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the case of oxidized astralenes, as expected, the presence of oxygen-containing groups in the structure leads to more pronounced destruction, which is evident from the DTG curve. Thus, the thermogravimetric curve for oxidized astralenes is characterized by a loss of 1.04% of the mass upon heating to 103℃, which is typical for the evaporation of moisture from the sample. The steps at temperatures of 156, 248, and 328℃ with mass losses of 0.31, 0.32, and 1.53%, respectively, can be attributed to the destruction of oxygen-containing groups on the surface of the particles [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The destruction step with a mass loss of 3.4% observed at a temperature of 464℃ is typical for the decomposition of disordered carbon in the material [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The destruction of the graphene surface layer in the oxidized astralenes can explain a fairly large destruction step at a temperature of 689℃ with a mass loss of 4.89% [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. When comparing this step in the oxidized astralenes with the original sample, it is clear that the mass loss is almost twice as high, even in the case of summing up the mass losses of the original sample at temperatures of 636, 679, 753 and 770 ℃. This result of the oxidized astralenes correlates with the fact that, as a result of the decomposition of oxygen-containing groups at lower temperatures, the graphene surface sheet contains a large number of defects, the presence of which facilitates its further destruction. As for the original astralene sample, the destruction step at a temperature of 796℃ with a mass loss of 6.62% for the oxidized astralenes can be associated with the destruction of the graphene layers [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eModified astralenes, like oxidized ones, are characterized by the presence of a greater number of mass loss stages, compared to the original particles. The first mass loss stage (the stage at 82℃ with a mass loss of 0.88%) is associated with the loss of adsorbed moisture on the sample. The second (121℃, 0.69%) and third (242℃, 0.75%) mass loss stages can be attributed to the destruction of oxygen-containing areas on the surface of modified astralenes [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. At temperatures of 312 and 457℃ (mass losses of 2.68 and 2.47%, respectively), the destruction of organic structures on the particle surface occurs, since these temperatures are characteristic of procaine destruction. The destruction of graphene layers (at a temperature of 802℃) for modified astralenes is more pronounced than the destruction of the surface layer of graphene (693℃), unlike oxidized astralenes, probably due to greater surface modification. As can be seen from the comparison of the TG analysis results, both stages of particle modification affect the outer graphene layer, somewhat reducing its thermal stability.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eThe influence of modified astralenes on the polymerization process\u003c/h2\u003e \u003cp\u003eThe effect of modified astralenes on the polymerization process was assessed using FTIR spectroscopy. For this purpose, the prepared monomer mixture was placed on the crystal of the NTR attachment, covered with a polyethylene terephthalate film to limit the contact of the reaction mass with atmospheric oxygen, and irradiated with a laser in the mode: λ\u0026thinsp;=\u0026thinsp;532 nm, I\u0026thinsp;=\u0026thinsp;200 \u0026micro;W/cm\u003csup\u003e2\u003c/sup\u003e, for 750 sec. In parallel with laser irradiation, FTIR spectra were recorded every 7.5 seconds, in which the intensity of the band at 1640 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, characteristic of vibrations of C\u0026thinsp;=\u0026thinsp;C bonds in monomer molecules, was monitored. Based on the change in the maximum intensity of this band over time, the kinetics of the polymerization process was calculated (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the experimental curves of photopolymerization processes. It is evident that with an increase in the concentration of particles in the reaction mass, the rate of the process of opening C\u0026thinsp;=\u0026thinsp;C bonds decreases, but the changes are not significant, and the observed values ​​of monomer conversion are comparable.\u003c/p\u003e \u003cp\u003eThe effect of additives of modified astralenes on the maximum rate of the polymerization process was also investigated (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFrom Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA it is seen that the undoped monomer mixture has the highest monomer conversion rate of 4.55%/sec, with an increase in the concentration of astralenes the maximum value decreases to 2.27, 1.98, 1.31%/sec, respectively. The observed slowdown in the polymerization process can be explained by a number of reasons. The authors of [\u003cspan additionalcitationids=\"CR21 CR22\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] observed similar results of a decrease in the polymerization rate, as well as a decrease in the degree of conversion with an increase in the proportion of carbon particles in the system. As described by the authors, compositions with a high filler content suffer from side effects associated with increased viscosity and a decrease in photocuring conversion. In [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], the optimal concentration of CNTs in a commercial photocurable resin was found to be up to 0.3 wt.%, above which the compositions lose good rapid polymerization capabilities, which is necessary for printing on a DLP printer. The authors of [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] observed inhibition of free radical polymerization while introducing C\u003csub\u003e60\u003c/sub\u003e fullerene and carbon nanotubes into the monomer mixture. As the authors describe, the reason for the inhibition is the formation of stable radicals with lower chemical activity as a result of the interaction of free radicals with carbon particles, which, due to the presence of a system of conjugated bonds, are capable of effectively delocalizing unpaired electrons of radicals. Since the polymerization process is initiated by radiation, the effect of fillers on the optical properties of the reaction mass is of no small importance. The authors of [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] showed that polymerization of a mixture with fillers slows down as a result of a decrease in the radiation intensity across the thickness due to light scattering. Especially in cases where the refractive index of the filler differs greatly from the refractive index of the monomers.\u003c/p\u003e \u003cp\u003eAlso, from Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA it is evident that when astralenes are added, the maximum polymerization rate is practically not shifted, but remains at a conversion value of ~\u0026thinsp;40%. At the same time, due to the decrease in the polymerization rate, the maximum rate shifts in time, and is 25, 53, 59 and 60 sec (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eFor a more detailed analysis of the influence of astralenes on the polymerization rate, the Sestak-Berggren equation was used [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. To simplify the calculations, the beginning of the polymerization process was considered - the section in which the conversion of monomers over time has a linear character (from 0 to 70 sec). Thus, it is possible to obtain a simplified autocatalytic kinetic model, from which it is possible to obtain the rate constant of the polymerization process (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\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\u003eEffect of modified astralenes on the polymerization process\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eContent of astralenes, % wt.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMonomer conversion, %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePolymerization rate, %/sec\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePolymerization rate constant\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e96.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e4.46719*10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e94.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e3.09309*10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e94.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e2.91599*10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e91.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e2.10068*10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\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\u003eIt is evident that the introduction of modified astralenes reduces the polymerization rate constant at the initial stage of the process by more than 40% on average. The obtained result is consistent with the results and assumptions given above.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eProperties of the polymer composite\u003c/h2\u003e \u003cp\u003eAs a result, polymer composite films were obtained by photopolymerization of a mixture of acrylates with modified astralenes. The thickness of the studied samples was 20 \u0026micro;m. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e shows the optical transmission of the obtained films.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIt can be seen that all samples are characterized by a comparable transmittance value of ~\u0026thinsp;90% in the visible spectrum and NIR range (500\u0026ndash;1100 nm).\u003c/p\u003e \u003cp\u003eBased on the obtained UV spectra, the optical band gap was calculated using the Tautz method (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\u003eOptical band gap values ​​of composites\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBand gap width, eV\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolymer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.93\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolymer\u0026thinsp;+\u0026thinsp;Astr_0.01%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.90\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolymer\u0026thinsp;+\u0026thinsp;Astr_0.05%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.90\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePolymer\u0026thinsp;+\u0026thinsp;Astr_0.10%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.89\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\u003eIt is evident that the introduction of such small additions of astralenes does not lead to a significant change in the band gap. The value characteristic of dielectric materials is retained.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eDuring the research, a successful modification of astralenes was achieved, leading to a decrease in the content of disordered carbon in the composition of the samples, as well as modification of the particle surface with various functional groups, which is confirmed by Raman and FTIR spectroscopy, TG analysis. At the same time, the toroidal structure of the particles is preserved, which is confirmed by TEM. It has been established that the modified particles are compatible with acrylic monomers and can be used to obtain composite polymer materials by photopolymerization filling. At the same time, the introduction of astralenes decreases the polymerization rate. At the initial stage of photopolymerization, a slowdown of more than 40% is observed. However, the degree of monomer conversion for acrylates with astralenes is comparable to the results obtained during polymerization of compositions without astralenes. All the obtained samples are characterized by similar transmission indices in the visible spectrum and NIR range, which indicates a uniform distribution of particles in the matrix volume. The optical band gap changes insignificantly when introducing astralene particles, the materials remain a dielectric.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eConflict of interest\u003c/strong\u003e \u003cp\u003eThe authors declare that they do not have any commercial or associative interest that\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eV.T. and J.B. participated in conceptualization of the article. V.T., J.B. and V.S. wrote the main text of the article. V.T. and A.I. developed the particle modification methodology. S.K. was involved in the transmission electron microscopy section. V.S. was involved in the FTIR spectroscopy and thermogravimetric analysis section. V.T., J.B., and V.S. were involved in studying the polymerization kinetics. V.T., J.B., and A.I. were involved in studying the optical properties of the composite. All five authors made revisions and approved the final text of the article.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors express their gratitude to the head of the laboratory of the Information Optical Technologies Center of ITMO University, Kirill Bogdanov, for measurements on the Raman spectrometer.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBurunkova JA, Alkhalil D, Svjazhina DS, Bony\u0026aacute;r A, Csarnovics I, Kokenyesi S Influence of gold nanoparticles in polymer nanocomposite on space-temporal-irradiation dependent diffraction grating recording. 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Polym Degrad Stab 94:1176\u0026ndash;1182. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.polymdegradstab.2009.02.014\u003c/span\u003e\u003cspan address=\"10.1016/j.polymdegradstab.2009.02.014\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\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":"polymer-bulletin","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pobu","sideBox":"Learn more about [Polymer Bulletin](http://link.springer.com/journal/289)","snPcode":"289","submissionUrl":"https://submission.nature.com/new-submission/289/3","title":"Polymer Bulletin","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Astralenes, acrylates, photopolymerization, optical composite","lastPublishedDoi":"10.21203/rs.3.rs-4866698/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4866698/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePolymers are a promising matrix for creating optical materials due to the possibility of imparting new properties to the material by introducing additives. In particular, astralenes, which are multilayer toroidal nanostructures, known as structure modifiers for some medium and also have nonlinear optical properties. Hower, the creation of an optical composite requires modification of the particle surface for uniform distribution of particles in the matrix. The two-stage modification technique developed by the authors allows reducing the amount of disordered carbon in the astralenes, as well as making them compatible with photocurable acrylic monomers. As a result, a transparent optical composite was obtained by photopolymerization. The success of the modification process is confirmed by the results of Raman and FTIR spectroscopy, TG analysis. The TEM method showed that the toroidal structure of the particles is preserved after the modification process. The study compared composites with 0.01, 0.05, 0.10%wt. astralenes and the original copolymer. It was found that the introduction of particles into the reaction mass reduces the polymerization rate by more than 40%. At the same time, the conversion degree in samples with and without astralenes is comparable. The transparency of the obtained composites in the visible region and NIR is comparable to the copolymer and is equal to ~\u0026thinsp;90%. The introduction of astralenes in the selected concentrations does not significantly affect the optical band gap of the material.\u003c/p\u003e","manuscriptTitle":"Surface modification of astralenes for obtaining optical composites based on photocurable acrylates","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-05 07:40:25","doi":"10.21203/rs.3.rs-4866698/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-01-02T05:26:03+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-12-12T09:55:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"155111946834988881777472137413211052633","date":"2024-12-12T06:30:27+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-09-17T02:31:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-09T08:00:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-08-07T06:24:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"Polymer Bulletin","date":"2024-08-06T08:08:23+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"polymer-bulletin","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pobu","sideBox":"Learn more about [Polymer Bulletin](http://link.springer.com/journal/289)","snPcode":"289","submissionUrl":"https://submission.nature.com/new-submission/289/3","title":"Polymer Bulletin","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"7cf70823-03bc-4efb-b264-e651017c5096","owner":[],"postedDate":"September 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-03-03T16:01:51+00:00","versionOfRecord":{"articleIdentity":"rs-4866698","link":"https://doi.org/10.1007/s00289-025-05684-9","journal":{"identity":"polymer-bulletin","isVorOnly":false,"title":"Polymer Bulletin"},"publishedOn":"2025-03-01 15:57:38","publishedOnDateReadable":"March 1st, 2025"},"versionCreatedAt":"2024-09-05 07:40:25","video":"","vorDoi":"10.1007/s00289-025-05684-9","vorDoiUrl":"https://doi.org/10.1007/s00289-025-05684-9","workflowStages":[]},"version":"v1","identity":"rs-4866698","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4866698","identity":"rs-4866698","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}