Antimicrobial activity of silver free powder coatings based on biocomponents

Antimicrobial activity of silver free powder coatings based on biocomponents | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Antimicrobial activity of silver free powder coatings based on biocomponents Katarzyna Krawczyk, Barbara Pilch-Pitera, Michał Kędzierski, Małgorzata Zubielewicz, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7099997/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted 11 You are reading this latest preprint version Abstract In this work, silver-free low-temperature curing epoxy powder coatings with antimicrobial properties were developed. To achieve this, the cationic biopolymer ε-polylysine (PLY) in its protonated form was used, along with intercalation products of PLY and co-intercalation products of PLY and aminododecanoic acid (ADA) in montmorillonite (MMT), as environmentally friendly alternative. The powder coatings were formulated using epoxy resin and a highly reactive phenolic curing agent. The resulting coatings were characterized in terms of surface roughness, gloss, scratch resistance, hardness, adhesion to steel, water contact angle, and antimicrobial resistance. A mechanism of antimicrobial activity was proposed. Physical sciences/Chemistry Physical sciences/Materials science polylysine montmoryllonite antimicrobial properties epoxy coatings powder coatings Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Polymeric materials with antimicrobial properties are increasingly used in healthcare, cosmetics, public spaces, and the food industry [1, 2, 3, 4]. However, concerns remain regarding the efficacy and environmental safety of biocidal additives. Key issues include selectivity without harming non-target organisms, minimizing bioaccumulation, and addressing antibiotic-resistant bacteria (“superbugs”) [5]. Antimicrobial coatings are typically classified as biocide-releasing, contact-killing, or anti-adhesive, with combinations often used for enhanced performance [6, 7]. In a comparative study of 23 commercial antimicrobial coatings, Mölling et al. [8] found that over half contained nanosilver and achieved log reductions of ~6 against E. coli (ISO 22196). Similar results were observed with coatings containing silver-TiO₂-MMT, zinc-MMT, TiO₂, covalently bound QACs, nanocurcumin/nanoclay systems, triclosan, and zinc pyrithione [9, 10, 11]. Silver's antimicrobial action is based on Ag⁺ ions binding to electron-donating groups in biomolecules such as membrane proteins and enzymes [12]. Despite strong antimicrobial properties, silver has disadvantages: high cost, limited resources, potential bioaccumulation, and induction of bacterial resistance [13, 14]. Moreover, nanosilver particles may trigger immunotoxic inflammatory responses [15, 16]. In coatings, silver use is limited by sensitivity to high curing temperatures and yellowing. To mitigate this, binary (Ag⁺/Cu²⁺) and ternary (Ag⁺/Cu²⁺/Zn²⁺) systems have been developed [17, 18], as well as combinations with organic antimicrobials like QACs or imidazole [19, 20]. QACs (R₁R₂R₃R₄N⁺X⁻) act through their hydrophobic chain, which disrupts microbial membranes, and a positively charged ammonium group that interacts with negatively charged cells [21]. They are effective against bacteria and enveloped viruses [22, 23]. However, microbial resistance to simple, widely used QACs has been reported [24]. Triclosan faces similar criticism due to environmental persistence, endocrine-disrupting effects, and potential photodegradation into toxic dioxins [25, 26]. Photocatalytic pigments like TiO₂ offer an alternative. Upon UV activation, TiO₂ produces reactive oxygen species (ROS) with cytotoxic effects [27]. ROS can inactivate multidrug-resistant bacteria, with Gram-negative strains generally more sensitive due to their thinner cell walls [28, 29]. Powder coating additives currently rely mostly on silver or nanosilver. Some silver-free systems using nano zinc oxide [30], nano titanium dioxide [31, 32], or bismuth compounds [33] have been proposed. However, metal-based nanoparticles may cause aggregation, phase separation, and toxicological issues, necessitating surface modification [34]. In contrast, natural antimicrobials are gaining attention. Chitosan has shown effectiveness in coatings [35]. ε-Poly-L-lysine (ε-PL), a biodegradable, cationic peptide of 25–35 L-lysine units [36], is water-soluble, non-toxic, and produced via microbial fermentation. It shows broad-spectrum antibacterial activity [37]. Its use as a preservative in aquatic food [38] and in biocompatible coatings [39] has been reported. Hu et al. developed ε-PL-modified titanium surfaces effective against multidrug-resistant bacteria [40]. Yuan et al. prepared antibacterial MMTs intercalated with ε-PL or its hydrochloride form, both active against E. coli and B. subtilis [41]. Similarly, Liao et al. designed ε-PL/chlorhexidine/MMT multilayer coatings effective against S. aureus [42]. Hybrid films with ε-PL, MMT, and gentamicin sulfate (GS) showed controlled, stimuli-responsive antibiotic release [43]. However, polylysine has not yet been explored in powder coatings. This study investigates the incorporation of ε-PL into epoxy-based powder coatings both in its pristine form and intercalated into MMT, with or without aminododecanoic acid (ADA). The goal is to evaluate the effects on antimicrobial, aesthetic, and mechanical performance, offering a sustainable silver-free alternative for antimicrobial protection. 2. Experimental Part 2.1. Preparation of antimicrobial agents (AA) and powder coatings Antimicrobial agents were prepared by intercalating ε-polylysine (PLY), with or without aminododecanoic acid (ADA), into sodium montmorillonite (MMT). The modified clays were incorporated into epoxy-based powder coatings and applied under control conditions. Details on synthesis, formulation, application, and curing are provided in the Supporting Information (Sections S1–S3). Table. 1. Qualitative/quantitative composition of the powder coatings Component/ Symbol of coating epoxy resin, wt % G-92, wt% benzoin Byk 368P PLY wt% PLY/MMT wt% PLY/MMT/ADA wt% EP (reference sample) 83,5 15,0 0,5 1,0 - - - PLY 82,0 14,5 0,5 1,0 2,0 - - PLY/MMT 82,0 14,5 0,5 1,0 - 2,0 - PLY/MMT/ADA 82,0 14,5 0,5 1,0 - - 2,0 2.4. Measurements Characterization included SEM, XRD, FTIR, TGA, DSC, DMA, SKP, profilometry, gloss, adhesion, hardness, and microbiological tests (EN ISO 22196). Full descriptions are provided in the Supporting Information (Sections S4–S6). 3. Results and Discussion 3.1. Antimicrobial agents’ characterization Polylysine (PLY) was used to impart antibacterial properties to powder coatings, either in its pristine form or after immobilization in montmorillonite (MMT) (Fig. 1). For the latter, two approaches were studied: intercalation of PLY from aqueous solution, and co-intercalation with aminododecanoic acid (ADA). Adding a second intercalant with a long alkyl chain, such as ADA, facilitates PLY intercalation. The 12-carbon chain penetrates the interlayer space of MMT, increasing the distance between the layers. This effect appears in the XRD pattern of ADA-intercalated MMT, where the (001) reflection shifts to lower 2θ angles—indicating an interlayer expansion from 12.8 Å (pristine MMT) to nearly 20 Å. Immobilizing polylysine in MMT may also reduce its leaching from the coating during prolonged moisture exposure. The PLY- and/or ADA-modified MMTs were characterized using elemental analysis, X-ray diffraction (XRD), and BET surface area measurements. Results are listed in Table 2 and shown in Fig. 2. Table. 2. Characteristics of components used in the study AA symbol C [%] H [%] N [%] C/N w/w Interlayer distance d 001 Å (XRD) Specific surface area m 2 /g (BET) PLY 39.87 8.024 15.00 2.66 - - MMT - - - - 12.8 29.67 ADA/MMT 18.30 3.40 2.20 8.32 19.91 12.73 PLY/MMT 7.11 2.033 3.00 2.37 13.9 20.19 PLY/MMT/ADA 7.88 2.167 2.81 2.80 14.0 (21) 21.91 Combustion elemental analysis revealed that both the carbon content and C/N weight ratio are significantly lower in PLY/MMT than in ADA/MMT, due to the higher carbon content of the long-chain amino acid. The co-intercalated PLY/MMT/ADA shows only a slight increase in these values compared to PLY/MMT but differs substantially from ADA/MMT. Given the similar BET surface areas and (001) reflection positions in the XRD spectra, polylysine appears to be the dominant intercalating species. A weak additional low-angle reflection at ~20 Å suggests that some long-chain amino acid molecules may also be partially incorporated between the MMT layers. To evaluate whether the newly developed antimicrobial components are thermally stable under the conditions of powder coating processing and curing, thermogravimetric analysis (TGA) was performed. The results are summarized in Table 3. Table 3. TGA results of used components AA symbol Decomposition temperature ranges / % wt. loss DTG max total % wt. loss at 700 ºC MMT 25-180 / 10 200-700 / 3 76.5 639 13 ADA 180-260 380-500 209 462 99 MMT/ADA 25-200 / 3 200-700 / 27 45 260, 297, 354 30 PLY 25-180 / 8 240-560/ 83 76 310,425,444 91 PLY/MMT 25-180 / 13 180-600 / 14 57 330, 470, 559 27 PLY/MMT/ADA 25-270 270-700 50 /5 331, 436, 556 20 The first stage of thermal decomposition of the raw materials and intercalated montmorillonites involves desorption of water adsorbed in the aluminosilicate interlayers. Water content depends on hydrophobicity—highest for PLY/MMT (13%) and lowest for MMT/ADA (3%). In sodium montmorillonite, the next mass loss occurs between 500–700 °C, attributed to clay dehydroxylation [ 1 ]. TGA of polylysine shows two main decomposition steps: 180–380 °C (65% mass loss) and above 380 °C (26%). Aminododecanoic acid also decomposes in two steps: the first at 180 °C (Hoffmann elimination of β-H) and the second at 400 °C, corresponding to degradation of the organic residue decomposes [ 2 ]. PLY leaves a higher char residue (9%), while ADA shows 99% total weight loss, likely due to its low molecular weight and high aliphatic carbon content. PLY intercalation into MMT results in a shift of the DTG peaks to higher temperatures, indicating improved thermal stability. Mass loss is greater above 380 °C (10%) than in the 180–380 °C range (4%). In contrast, ADA shows reduced decomposition temperatures after intercalation, consistent with Liu et al., who attributed this to the catalytic effect of montmorillonite’s solid acidity on ALA degradation [ 3 ]. The co-intercalation product PLY/MMT/ADA displays thermal behavior similar to PLY/MMT but yields a higher char residue (80%) than ADA/MMT (70%) or PLY/MMT (73%). The powder coating process was conducted at 115 °C, with curing at 130 °C. TGA results confirm that only moisture is released within this range. Above 130 °C, the mass remains stable up to ~180 °C, confirming the thermal stability of the antimicrobial systems under typical powder coating conditions. The chemical structure of the obtained antimicrobial agents was confirmed by FTIR spectra provided in the Supporting Information (Section S7). The FTIR spectra of PLY/MMT and PLY/MMT/ADA are dominated by bands of montmorillonite at about 1000 cm −1 , which is related to the stretching vibrations of the Si-O bonds, as well as by the weaker band at about 3620 cm −1 , which is attributed to stretching vibrations of O-H bonds (Figs. S7.1b and S7.1c) [ 4 ] . These FTIR spectra contain also additional peaks near 3230 cm −1 , 2935 cm −1 , 1670 cm −1 and 1550 cm −1 , which are derived from polylysine (Fig. S7.1a) and correspond respectively to the vibrational modes of the amide group and protonated -NH 3 + side chain groups stretching vibration [ 5 , 6 ]. This confirms the protonation of nitrogen atoms in polylysine, which enables interaction between -NH 3 + groups and negatively charged sites of montmoryllonite (MMT). The presence of protonated ammonium groups is also a key factor influencing antibacterial properties of polylysine. The morphology of antimicrobial additives were investigated by SEM (Fig. 3). Antimicrobial additives based polylysine were characterized by different morphology depending on the treatment used. Pure polylysine particles were characterized by a near-spherical shape and had a slightly developed surface. The size of the powder particles ranges from about 5-100 μm. Polylysine particles immobilized on sodium montmorillonite have a noticeably more developed surface and a size in the range of about 1-40 μm. Particles of polylysine powder immobilized on MMT modified with aminedodecanoic acid are characterized by a similar size to the unmodified variant, show a developed surface area and. Additionally, these particles tended to form agglomerates on the surface of larger powder particles. 3.2. Powder coatings characterisation Powder coatings were prepared with polylysine, either alone or intercalated on MMT, as well as co-intercalated with ADA. Intercalation aimed to enhance dispersibility of the modifier in the powder coating, improve compatibility with the polymer matrix, and increase washing resistance. Coatings were cured at 130°C for 10 min, during which epoxy groups from the resin reacted with a phenolic curing agent E011. The cross-linked coatings were tested for visual, mechanical, and antibacterial properties. Coatings free of defects such as orange peel, cratering, or pinholes were achieved. Their properties are detailed in Table 4. Table 4. Specifications of coatings properties. Symbol of coating EP PLY PLY/MMT PLY/MMT/ADA Roughness EN ISO 12085 R a , µm R z , µm 0.82±0.02 5.01±0.16 0.21±0.02 1.38±0.12 0.36±0.02 2.75±0.17 0.18±0.03 0.95±0.18 Gloss for the angle of 60deg EN ISO 2813 GU 72.3±1.2 104.9±1.5 74.2.1±0.9 99.8±2.6 Scratch resistance EN ISO 1518 g 400 400 300 300 Relative hardness EN ISO 1522 - 0.80±0.02 0.90±0.02 0.83±0.03 0.86±0.03 Adhesion to the steel EN ISO 2409 0-best 5-worst 0 0 0 0 Cupping ISO 1520 mm 8.70±0.01 4.02±0.01 8.74±0.01 9.35±0.01 Water contact angle EN 828 deg 89.0±1.2 87.7±1.1 89.1±1.2 88.2±1.4 Reduction of E. coli EN ISO 22196 Log reduction % reduction Ref. sample: log total number of cells 4,32±0.002 4.80±0.01 99.998±0.010 2.52±0.04 99.698±0.057 0.15±0.01 29.77±0.03 Reduction of S. aureus EN ISO 22196 Log reduction % reduction Ref. sample: log total number of cells 4,77±0.001 2.57±0.03 99.733±0.035 0.33±0.01 52.881±0.003 0.15±0.01 30.00±0.04 The surface coatings roughness was determined as average parameters R a and R z . The roughness values for all samples were characteristic for smooth coatings. However, roughness of reference sample (R a = 0.82±0.02 µm, R z = 5.01±0.16 µm) were higher than modified coatings. The addition of polylysine reduces the coating roughness, which indicates an increase of homogeneity. As a result of modification with polylysine intercalated on MMT, a slight increase in surface roughness was observed in comparison to PLY sample, which indicates a decrease of homogeneity in this coating resulting from the difference in interactions between the resin and MMT particles with a more hydrophilic structure. The addition of polylysine immobilized on MMT modified with aminodecanoic acid affects the reduction of roughness due to the presence of the hydrophobic ADA chain, which causes an increase in homogeneity with epoxy matrix. In addition to the roughness values determined by using a stylus profilometer (Table 4), complementary surface roughness measurements were performed using a laser scanning microscope (LSM) (Fig. 4). This technique enables high-resolution, three-dimensional visualization of the surface topography and provides numerical values for roughness parameters such as Ra and Rz. The results for selected coatings are summarized below: PLY: Ra = 0.680 µm, Rz = 9.32 µm PLY/MMT: Ra = 2.932 µm, Rz = 42.35 µm PLY/MMT/ADA: Ra = 2.579 µm, Rz = 43.91 µm These values confirm the trends observed with stylus profilometry: coatings modified with nanofillers such as MMT and ADA exhibit higher surface roughness compared to the unmodified PLY formulation. This is attributed to the presence of dispersed filler particles on the surface, which increase topographical variations. Laser scanning microscopy (LSM) surface analysis revealed that the unmodified coating (PLY) had the lowest roughness (Ra = 0.680 µm; Rz = 9.32 µm). In contrast, nanocomposites PLY/MMT and PLY/MMT/ADA showed significantly higher roughness, with Ra values of 2.932 µm and 2.579 µm and PLY/MMT/ADA (Ra = 2.579 µm; Rz = 43.91 µm) displayed significantly increased roughness. These results suggest that the incorporation of MMT and ADA leads to a more pronounced surface texture, likely due to particle agglomeration or protrusions, resulting in less uniform films that may affect barrier properties and adhesion. 3D LSM images support this by showing different surface features and filler distribution between the composites. In summary, LSM-based roughness analysis complements stylus profilometry by providing spatially resolved, microstructural information. The combination of both techniques offers a comprehensive understanding of the correlation between surface topography and coating performance. The gloss of the coatings depended on their roughness. Coatings with lower roughness had higher gloss values. All coatings demonstrated good scratch resistance. Samples containing PLY showed scratch resistance at the same level as the reference sample. For coatings with MMT, lower scratch resistance values were observed, which is due to the low hardness of MMT (1.5 on the Mohs scale). Adding polylysine resulted in an increase in relative hardness compared to the epoxy-based reference sample, likely because of their stiffer chains and additional stiffening hydrogen bonds. Furthermore, during the coating cross-linking process, the epoxy groups from the epoxy resin may react with the amino groups of polylysine, causing cross-linking and increasing hardness [ 7 ]. For MMT-containing samples, hardness also increased compared to the reference, but was slightly lower than the PLY coating, due to the hard lamellar structure of MMT. Samples with polylysine are less resistant to cupping, possibly because of its linear structure affecting the tribological properties of the crosslinked epoxy matrix. MMT samples are more resistant to cupping thanks to the stronger bonds of Si-O (1096 kJ/mol) and Al-O (957 kJ/mol) in MMT, compared to bonds in the epoxy matrix like C-C (347 kJ/mol), C-H (415 kJ/mol), and C-O (360 kJ/mol), which increases this parameter [ 8 ]. Adhesion to the steel surface was high, thanks to polar functional groups such as secondary hydroxyls formed during the epoxy curing process with the polyphenol curing agent. These hydroxyl groups interact electrostatically with the steel substrate, boosting adhesion. In the PLY-containing sample, a decrease in contact angle was observed, reflecting its more hydrophilic nature. The presented data show that the sample containing polylysine has very high antibacterial activity against E. coli, with a reduction of 99.998%, but slightly lower activity against S. aureus at 99.733%. This suggests PLY is more effective against Gram-negative bacteria, likely due to differences in cell wall structure. When immobilized on MMT, PLY still effectively reduces E. coli, but has a much lower effect on S. aureus. Amino acid co-intercalation further decreases activity, resulting in about a 30% reduction for both bacterial strains. The effect of antimicrobial agents on the behavior of powder coatings during controlled heating was investigated using the DSC and DMA technique (Fig. 5 and Fig. 6). On the DSC curves recorded during the first heating of the samples, a glass transition with relaxation occurred and the glass transition temperature was determined, which for the EP reference sample was 102.3°C (Fig. 5a). For the samples containing 2 wt.%, the addition of the biocide compositions PLY/MMT and PLY/MMT/ADA (Fig. 5a) had no effect on the glass transition temperature, which was 102.6°C and 102.1°C, respectively. There was a clear effect of the addition of 2 wt.% polylysine (Fig. 5a) on lowering the glass transition temperature of the EP binder by 10.9°C relative to that of the reference sample. PLY which interacts with EP may be responsible for this condition. Chen et al. [ 9 ] described that PLY interacts with C-O groups in EP via NH groups. The authors describe that this effect is visible in the glass transition temperature value. Shukla et al. [ 10 ] reported that the glass transition temperature of microbial crystalline poly(ε-L-lysine) is 88°C. It should be noted that lysine and lysine-based (amino-functionalized polyester) polyesters exhibit tunable thermal properties i.e. glass transition, melting point, which increases with increasing M n of the amino-functionalized polyester. The glass transition temperature of the reference sample, determined from the DSC curve recorded at the second heating stage, was 105.5°C compared to 106.5°C for the PLY/MMT sample and 105.2°C for the PLY/MMT/ADA sample (Fig. 5b). The slight differences in the determined values are due to the removal of thermal history and stress in the coating samples tested. The sample containing 2 wt.% PLY had a lower glass transition temperature value of 97.9°C. The difference in Tg value between the 2 wt.% PLY sample and the reference sample decreased in the second heating because of the ordering of the binder structure of the PLY-containing sample. The dynamic mechanical analysis showed that the glass transition was the predominant transition recorded during the tests performed. The value of the peak of the mechanical loss factor (tan δ) was taken as the glass transition temperature. For the reference sample, the glass transition was determined at 107.3°C Fig. 6a). Very similar values were obtained for the MMT/PLY and MMT/PLY/ADA samples at 107.7°C and 108.1°C respectively (Figs. 6c and 5d). The lowest glass transition temperature was 91.7°C for the sample containing 2 wt% PLY (Fig. 6b). This sample had the lowest intensity of the tan δ peak, indicating good attenuation/damping properties. The other samples had similar tan δ intensities. The analysis of the storage modulus values is also significant, from which it can be concluded that the samples underwent relaxation and intramolecular reorganization of the EP matrix at an early stage of the test, followed by vitrification, and that at a higher temperature the samples were in an elastic state, as evidenced by the low storage modulus value. The influence of MMT and ADA in the MMT/PLY/ADA sample is also evident, with the MMT/PLY/ADA sample showing the highest storage modulus of the samples tested (approximately 700 MPa versus 550 MPa for the reference sample, 600 MPa for PLY and 450 MPa for MMT/PLY), indicating the highest energy storage capacity of the samples tested and the higher stiffness of the sample in the dynamic shear deformation mode. To investigate the elemental distribution and homogeneity of antimicrobial coatings, SEM/EDS mapping and quantification were performed for three formulations: PLY, PLY/MMT, and PLY/MMT/ADA. Table 5. Elemental composition (in weight %) of powder coatings containing polylysine (PLY), polylysine immobilized in montmorillonite (PLY/MMT), and polylysine immobilized in montmorillonite modified with aminododecanoic acid (PLY/MMT/ADA), as determined by EDS spectroscopy. Element Weight %_ PLY Weight %_ PLY/MMT Weight %_PLY/MMT/ADA CK 21,81 75,54 23,52 OK 18,36 3,95 28,74 FeI 1,34 0,33 1,88 AlK 2,05 0,03 9,43 SiK 0,33 0,29 23,49 AuM 20,98 19,84 10,45 NK 0,27 0,08 KK 0,26 NaK 0,15 BaI 29,08 SK 5,77 MgK 0,01 1,47 The elemental composition and distribution of the antimicrobial powder coatings were evaluated by EDS spectroscopy and are summarized in Table 5. For the PLY system, the EDS spectrum revealed a high carbon content (~74.6 wt%) along with notable amounts of oxygen (11.8 wt%), nitrogen (2.2 wt%), and sulfur (5.4 wt%). The presence of nitrogen and sulfur is consistent with the chemical structure of polylysine and the epoxy resin. The elemental mapping indicates a homogeneous distribution of components, suggesting uniform film formation. Minor traces of elements such as Na, Al, and Si are likely attributable to the substrate or incidental contamination. In the PLY/MMT formulation, the successful incorporation of montmorillonite is evidenced by a significant increase in silicon (13.4 wt%) and aluminum (2.6 wt%), while the carbon content slightly decreases (~75.6 wt%) due to the inorganic nature of the filler. Oxygen content is elevated, reflecting contributions from the silicate framework. Mapping data reveal distinguishable montmorillonite agglomerates with locally increased density, yet overall dispersion remains relatively even. The consistent nitrogen signal suggests that polylysine remains well distributed throughout the matrix. For the PLY/MMT/ADA system, the oxygen (21.6 wt%) and nitrogen (4.2 wt%) contents increase further, reflecting the additional functional groups introduced by aminododecanoic acid (ADA). The carbon content drops to ~31.5 wt%, while Si and Al levels remain comparable to the PLY/MMT sample, indicating a stable montmorillonite fraction. The mapping shows localized clusters that may correspond to ADA-rich domains or phase-separated regions. These inhomogeneities are also visible as distinct contrast variations in SEM images. Such segregation may influence both the electrochemical surface behavior (as evidenced by SKP measurements) and the availability of antimicrobial agents [54,55]. The surface potential distribution of antimicrobial powder coatings was investigated using SKP measurements to evaluate the influence of polylysine and its combinations with montmorillonite (MM) and aminododecanoic acid (ADA) on electron transfer characteristics at the surface (Fig. 8). For the PLY system, the surface potential ranged from approximately 0.46 V to 0.56 V, with a slight positive gradient across the scanned area (Fig. 8a). This indicates a mildly electron-enriched surface, which may promote initial oxygen reduction, followed by the formation of a positively charged electrical double layer that limits further redox activity. In contrast, the PLY/MMT sample exhibited a clear negative slope in surface potential, decreasing from ~1.3 V to 1.0 V across the surface (Fig. 8b). This behavior suggests that the interaction between polylysine and the montmorillonite matrix induces electron depletion and enhanced band bending, which can reduce surface reactivity, particularly toward oxygen adsorption and reduction. The most pronounced behavior was observed in the PLY/MMT/ADA sample (Fig. 8c). Here, the surface potential exhibited a sharp gradient, ranging from above +12 V to below +2 V, with localized charge accumulation particularly evident in the lower-left region of the map. This extreme potential inhomogeneity may result from phase separation or the formation of microdomains. The pronounced lateral potential differences and steep voltage drops indicate strong spatial variation in electron distribution, likely leading to reduced electron mobility. Such effects may contribute to the diminished antimicrobial performance observed in this formulation. These findings highlight how the surface electrochemical landscape of antimicrobial powder coatings can be tuned by additive combination. While pure polylysine enhances surface electron availability, its combination with layered fillers and co-additives introduces structural and electronic complexity that may impair surface reactivity. The combination of SKP results with previously shown EDS data suggests a correlation between chemical homogeneity and surface potential stability: PLY: homogeneous structure, stable surface potential PLY/MMT: moderate agglomeration, downward potential trend PLY/MMT/ADA: visible inhomogeneities, sharp potential gradients and localized charge accumulation These findings underline that while additive combinations like MMT and ADA may enhance certain physical properties, they can lead to microphase separation, affecting charge transport and possibly reducing antimicrobial efficiency. 3.3. Washing resistance of antibacterial additives To initially determine the resistance of powder coatings to the leaching of antibacterial additives, we investigated the changes in water conductivity when in contact with the cured coating over time. Conductometric analysis of the washing resistance of powder coatings containing PLY, PLY/MMT, and PLY/MMT/ADA was provided in the Supporting Information (Section S8). In the case of coatings containing polylysine alone, a significant increase in conductivity values is observed after 5 to 7 days, indicating the gradual dissolution of the polymer containing ionic groups. Immobilization on MMT significantly reduces polylysine leaching for three weeks, followed by a rise in water conductivity. In contrast, the co-intercalation product PLY/MMT/ADA shows no increase in conductivity compared to the coating without biocide, even after 25 days, emphasizing the stabilizing role of amino acid modification 3.4. Mechanism of antimicrobial action The antimicrobial activity of powder coatings containing polylysine and its combinations with montmorillonite (MM) and amino dodecanoic acid (ADA) can be explained by a combination of physicochemical interactions at the coating–microorganism interface. According to the studies of Nigmatullin et al., the intercalation compounds of montmorillonite with cationic polymers exhibit two modes of antimicrobial activity: the migration of the biocide to the surface and contact-killing of bacteria through interaction with immobilized cationic species on the surface. The diffusion of the biocide is rather slow, and the contact mechanism plays the dominant role [56] . Based on previous studies and the newly obtained SKP and EDS data, three main mechanisms are considered (Fig. 9): 1. Electrostatic attraction and surface charge modulation: Bacterial cell membranes are usually negatively charged. Coatings with cationic agents like polylysine create a positive surface, increasing attraction of microbial cells. SKP measurements of the PLY system confirm a relatively uniform, slightly positive surface, promoting bacterial adhesion and charge interactions that may destabilize the membrane and trigger antimicrobial activity. In contrast, incorporating montmorillonite (PLY/MMT) alters surface potential. Clay layered structure has negative charges, causing electron depletion and lowering surface potential. This redistributes charge, reducing electrostatic attraction between the coating and bacteria, impairing microbial interaction. (2) Ionic imbalance and membrane damage: In the PLY/MMT/ADA system, SKP contour plots show strong potential gradients and areas of high surface charge. These may create local electric fields disrupting osmotic balance across bacterial membranes, causing ion and water leakage, membrane rupture, and cell death. This is supported by inhomogeneity in elemental distribution (seen in EDS mapping), indicating partial phase separation of ADA domains. (3) Inhibition of redox processes and potential oxidative stress: Electron transfer reactions, especially oxygen reduction on the coating surface, are affected by surface potential. In PLY coating, a moderate positive potential might permit limited redox activity. However, the sharp potential drop in PLY/MMT/ADA indicates an electron-depleted surface state, making oxygen reduction unlikely. This surface may hinder electron transfer processes, potentially interfering with microbial respiration processes. Localized high-potential zones may also generate reactive oxygen species (ROS), damage cells and disrupting metabolism. In summary, the antimicrobial effectiveness of polylysine coatings depends on the additive's chemistry, surface potential, and distribution. A homogeneous, moderately positive potential, as observed for PLY, seems most favorable for electrostatic interaction and antimicrobial activity. Composites with MMT and ADA may cause inhomogeneity, reducing biocidal performance. 4. Conclusions In this study, silver-free antimicrobial powder coatings based on epoxy resin and the cationic biopolymer polylysine were successfully developed and characterized. Polylysine was applied in three different forms: as a pure additive, intercalated in montmorillonite (PLY/MMT), and co-intercalated with aminododecanoic acid (PLY/MMT/ADA). The aim was to enhance antimicrobial efficacy, reduce leaching, and improve compatibility within the coating matrix. Comprehensive physicochemical characterization—including FTIR, XRD, TGA, DSC, DMA, SEM/EDS, and SKP—demonstrated that the structure and distribution of the additives significantly influence thermal stability, mechanical properties, and surface electrochemical behavior. Pure polylysine improved coating homogeneity and provided a stable, moderately positive surface potential, favorable for electrostatic interaction with bacterial membranes. The addition of montmorillonite increased thermal resistance and hardness but introduced surface potential gradients and reduced antimicrobial performance. Co-intercalation with ADA improved leaching resistance and mechanical reinforcement yet led to charge inhomogeneity that may interfere with biological activity. The results suggest that antimicrobial effectiveness may be influenced not only by the chemical composition of the additive but also by its electrochemical surface distribution under the given test conditions. Coatings with uniform cationic groups and stable surface potentials—like the system with only PLY—showed the highest antibacterial activity among the tested systems under laboratory conditions. Using polylysine, a biodegradable and renewable biopolymer, supports the development of sustainable biomaterials for antimicrobial applications. While the coatings demonstrated promising antimicrobial and mechanical properties in controlled laboratory settings, the study does not include long-term durability tests, environmental aging, or resistance against a broader spectrum of microorganisms. These aspects should be addressed in future work to assess real-word applicability and stability of the systems. Furthermore, eliminating silver may contribute to improved resource efficiency in designing antimicrobial coatings. Declarations Funding This work was supported by the AiF and the NCBR within the CORNET programme (Project No. 363 EN; 01IF00363C, acronym: MicroSafeCoatings – Novel antimicrobial protection in powder coatings for composite materials), and by the Ministry of Science and Higher Education of the Republic of Poland under the programme “Regional Excellence Initiative”, grant number RCD.RB.24.002.01. Acknowledgments: The authors would like to thank Sarzyna Chemie, Allnex and BYKChemie for sending free samples of raw materials. Data Availability All data generated or analysed during this study are included in this published article and its supplementary information files. Additional data is available from the corresponding author on reasonable request. References A.M. Pagtalunan, F.C. Sumera, M.T. Conato, Synthesis and characterization of 12-aminolauric acid-modified montmorillonite for catalytic application, AIP Conf. Proc. 1958 (2018) 020021. https://doi.org/10.1063/1.5034552. J. Zhu, A.B. Morgan, F.J. Lamelas, C.A. Wilkie, Fire Properties of Polystyrene−Clay Nanocomposites, Chem. Mater. 13 (2001) 3774-3780. https://pubs.acs.org/doi/10.1021/cm000984r. H. Liu, P. Yuan, D. Liu, et al., Effects of solid acidity of clay minerals on the thermal decomposition of 12-aminolauric acid, J. Therm. Anal. Calorim. 114 (2013) 125–130. https://doi.org/10.1007/s10973-012-2887-0. K. Kelar, B. Jurkowski, K. Mencel, Montmorylonit wyodrębniany z bentonitu — modyfikacja i możliwości wykorzystania w polimeryzacji anionowej ɛ-kaprolaktamu do otrzymywania nanokompozytów, Polimery 50 (2005), 449-454. M. Rozenberg, G. 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Wang, New bio-renewable polyester with rich side amino groups from L-lysine via controlled ring-opening polymerization, Polymer Chemistry 5 (2014) 6495. DOI: 10.1039/c4py00930d S.C. Shukla, A. Singh, A.K. Pandey, A. Mishra, Review on production and medical appications of ε-polylisine, Biochemical Engineering Journal 65 (2012) 70-81. DOI: 10.1016/j.bej.2012.04.001. N. Kitadai, T. Yokoyama, S. Nakashima, In situ ATR-IR investigation of L-lysine adsorption on montmorillonite, Geochimica et Cosmochimica Acta 73 (2009) (13, Supplement), A687. https://doi.org/10.1016/j.jcis.2009.06.061. C. Boahen, S. Wiafe, F. Owusu, L. Bian, Adsorption of heavy metals from mine wastewater using amino-acid modified Montmorillonite, Geochimica et Cosmochimica Acta 73 (2023) (13, Supplement) A687. https://doi.org/10.1080/27658511.2022.2152590. R. Nigmatullin, F. Gao & V. Konovalova, Polymer-layered silicate nanocomposites in the design of antimicrobial materials. J Mater Sci 43, 5728–5733 (2008). https://doi.org/10.1007/s10853-008-2879-4 Additional Declarations No competing interests reported. Supplementary Files SupportingInformation110725.pdf Cite Share Download PDF Status: Published Journal Publication published 02 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 14 Oct, 2025 Reviews received at journal 12 Oct, 2025 Reviews received at journal 26 Sep, 2025 Reviewers agreed at journal 21 Sep, 2025 Reviewers agreed at journal 17 Sep, 2025 Reviewers agreed at journal 17 Aug, 2025 Reviewers invited by journal 30 Jul, 2025 Editor assigned by journal 30 Jul, 2025 Editor invited by journal 30 Jul, 2025 Submission checks completed at journal 28 Jul, 2025 First submitted to journal 28 Jul, 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. 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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-7099997","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":494741002,"identity":"dcec841b-bd00-4f74-a903-7246f9ccd46e","order_by":0,"name":"Katarzyna 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Industrial Chemistry Institute","correspondingAuthor":false,"prefix":"","firstName":"Marta","middleName":"","lastName":"Przybysz-Romatowska","suffix":""},{"id":494741017,"identity":"6cffef0d-4c8a-4383-9957-43f0e543b661","order_by":11,"name":"Michael Hilt","email":"","orcid":"","institution":"Fraunhofer Institute for Manufacturing Engineering and Automation","correspondingAuthor":false,"prefix":"","firstName":"Michael","middleName":"","lastName":"Hilt","suffix":""}],"badges":[],"createdAt":"2025-07-11 09:23:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7099997/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7099997/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-30166-3","type":"published","date":"2025-12-02T15:57:27+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88284633,"identity":"2571dd0d-0340-4a3d-a944-0caecc9916fb","added_by":"auto","created_at":"2025-08-04 22:28:04","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":315464,"visible":true,"origin":"","legend":"\u003cp\u003eImobilisation of ε-polylysine into sodium montmorillonite (Na⁺-MMT) to form biofunctional PLY/MMT nanohybrids with antimicrobial properties.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/06a68f476d4225b297e2bdaa.png"},{"id":88284742,"identity":"475ce9ac-cf51-4a63-95a2-6152d4b4628a","added_by":"auto","created_at":"2025-08-04 22:36:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":430733,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray diffraction patterns of MMT intercalated compounds: a) aminododecanoic acid, b) polylysine and c) co-intercalation of polylysine and aminododecanoic acid\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/8020c1150a845e705099068e.png"},{"id":88284649,"identity":"c5bd4a77-50f6-44c2-8f89-bcce027a2226","added_by":"auto","created_at":"2025-08-04 22:28:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":815684,"visible":true,"origin":"","legend":"\u003cp\u003eSEM morphology of antimicrobial additives: a) polylysine (PLY), b) polylysine immobilized on sodium montmorillonite (PLY/MMT) and c) polylysine immobilized on aminedodecanoic acid intercalated on MMT (PLY/MMT/ADA)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/266b07780c463e7a71c2d637.png"},{"id":88284637,"identity":"d45ecd26-a77d-4ae7-8a7d-dcdaff7965d9","added_by":"auto","created_at":"2025-08-04 22:28:04","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1040425,"visible":true,"origin":"","legend":"\u003cp\u003eSurface images and profiles of selected coatings obtained via laser scanning microscopy (LSM). The visualizations show surface morphology and topographical variations for the PLY, PLY/MMT, and PLY/MMT/ADA formulations.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/b2c9397ecefc1d8d8811dae0.png"},{"id":88284639,"identity":"1ac70231-5376-47e8-a492-793d73a778c6","added_by":"auto","created_at":"2025-08-04 22:28:04","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":206349,"visible":true,"origin":"","legend":"\u003cp\u003eDSC curves recorded during a) the first heating, b) the second heating\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/2caf4ad30b0eea3ba1132ccd.png"},{"id":88284634,"identity":"7e673320-ddaf-48ed-8bcc-5fd1ace318bc","added_by":"auto","created_at":"2025-08-04 22:28:04","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":359930,"visible":true,"origin":"","legend":"\u003cp\u003eDMA curves of the samples: a) reference sample without microbial additives, \u003cbr\u003e\nb) sample with polylysine (PLY), c) with polylysine immobilized in montmorillonite (PLY/MMT), d) with polylysine immobilized in montmorillonite with aminododecanoic acid (PLY/MMT/ADA)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/5f46124cf884160811720f8e.png"},{"id":88284664,"identity":"71da85a5-9be7-4cf1-adc7-19c4c1f4ddef","added_by":"auto","created_at":"2025-08-04 22:28:06","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":2337632,"visible":true,"origin":"","legend":"\u003cp\u003eEDS microscopy images combined with elemental mapping of powder coatings: a) PLY, b) PLY/MMT, and c) PLY/MMT/ADA\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/917df289dfb53226fe63f8e3.png"},{"id":88284690,"identity":"977512e6-7184-4d55-a4d8-04acc8f108b9","added_by":"auto","created_at":"2025-08-04 22:28:07","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":534556,"visible":true,"origin":"","legend":"\u003cp\u003eSurface potential distribution of antimicrobial powder coatings measured by Scanning Kelvin Probe (SKP): a) PLY, b) PLY/MMT, and c) PLY/MMT/ADA\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/7835d112db5a467a9d647104.png"},{"id":88284662,"identity":"111d187a-6a4f-49c1-83a3-2c6e83a832d0","added_by":"auto","created_at":"2025-08-04 22:28:06","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":944262,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of proposed antibacterial mechanisms of PLY/MMT systems, created by the authors using Microsoft PowerPoint.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/9059c8aec2e34b9f29ebe2b8.png"},{"id":97723816,"identity":"16cd3f06-765e-43a4-bc47-a3ebbda07c6c","added_by":"auto","created_at":"2025-12-08 16:07:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8851051,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/f93ff7b2-08ee-4b1b-b0c5-98d757d8e5c4.pdf"},{"id":88284631,"identity":"33834b74-b41d-4062-b38b-95872d2ae327","added_by":"auto","created_at":"2025-08-04 22:28:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":827934,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation110725.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7099997/v1/e44a081f6117d7de4b292eb2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Antimicrobial activity of silver free powder coatings based on biocomponents","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePolymeric materials with antimicrobial properties are increasingly used in healthcare, cosmetics, public spaces, and the food industry [1, 2, 3, 4]. However, concerns remain regarding the efficacy and environmental safety of biocidal additives. Key issues include selectivity without harming non-target organisms, minimizing bioaccumulation, and addressing antibiotic-resistant bacteria (\u0026ldquo;superbugs\u0026rdquo;) [5].\u003c/p\u003e\n\u003cp\u003eAntimicrobial coatings are typically classified as biocide-releasing, contact-killing, or anti-adhesive, with combinations often used for enhanced performance [6, 7]. In a comparative study of 23 commercial antimicrobial coatings, M\u0026ouml;lling et al. [8] found that over half contained nanosilver and achieved log reductions of ~6 against \u003cem\u003eE. coli\u003c/em\u003e (ISO 22196). Similar results were observed with coatings containing silver-TiO₂-MMT, zinc-MMT, TiO₂, covalently bound QACs, nanocurcumin/nanoclay systems, triclosan, and zinc pyrithione [9, 10, 11].\u003c/p\u003e\n\u003cp\u003eSilver\u0026apos;s antimicrobial action is based on Ag⁺ ions binding to electron-donating groups in biomolecules such as membrane proteins and enzymes [12]. Despite strong antimicrobial properties, silver has disadvantages: high cost, limited resources, potential bioaccumulation, and induction of bacterial resistance [13, 14]. Moreover, nanosilver particles may trigger immunotoxic inflammatory responses [15, 16]. In coatings, silver use is limited by sensitivity to high curing temperatures and yellowing. To mitigate this, binary (Ag⁺/Cu\u0026sup2;⁺) and ternary (Ag⁺/Cu\u0026sup2;⁺/Zn\u0026sup2;⁺) systems have been developed [17, 18], as well as combinations with organic antimicrobials like QACs or imidazole [19, 20].\u003c/p\u003e\n\u003cp\u003eQACs (R₁R₂R₃R₄N⁺X⁻) act through their hydrophobic chain, which disrupts microbial membranes, and a positively charged ammonium group that interacts with negatively charged cells [21]. They are effective against bacteria and enveloped viruses [22, 23]. However, microbial resistance to simple, widely used QACs has been reported [24]. Triclosan faces similar criticism due to environmental persistence, endocrine-disrupting effects, and potential photodegradation into toxic dioxins [25, 26].\u003c/p\u003e\n\u003cp\u003ePhotocatalytic pigments like TiO₂ offer an alternative. Upon UV activation, TiO₂ produces reactive oxygen species (ROS) with cytotoxic effects [27]. ROS can inactivate multidrug-resistant bacteria, with Gram-negative strains generally more sensitive due to their thinner cell walls [28, 29].\u003c/p\u003e\n\u003cp\u003ePowder coating additives currently rely mostly on silver or nanosilver. Some silver-free systems using nano zinc oxide [30], nano titanium dioxide [31, 32], or bismuth compounds [33] have been proposed. However, metal-based nanoparticles may cause aggregation, phase separation, and toxicological issues, necessitating surface modification [34].\u003c/p\u003e\n\u003cp\u003eIn contrast, natural antimicrobials are gaining attention. Chitosan has shown effectiveness in coatings [35]. \u0026epsilon;-Poly-L-lysine (\u0026epsilon;-PL), a biodegradable, cationic peptide of 25\u0026ndash;35 L-lysine units [36], is water-soluble, non-toxic, and produced via microbial fermentation. It shows broad-spectrum antibacterial activity [37]. Its use as a preservative in aquatic food [38] and in biocompatible coatings [39] has been reported. Hu et al. developed \u0026epsilon;-PL-modified titanium surfaces effective against multidrug-resistant bacteria [40].\u003c/p\u003e\n\u003cp\u003eYuan et al. prepared antibacterial MMTs intercalated with \u0026epsilon;-PL or its hydrochloride form, both active against \u003cem\u003eE. coli\u003c/em\u003e and \u003cem\u003eB. subtilis\u003c/em\u003e [41]. Similarly, Liao et al. designed \u0026epsilon;-PL/chlorhexidine/MMT multilayer coatings effective against \u003cem\u003eS. aureus\u003c/em\u003e [42]. Hybrid films with \u0026epsilon;-PL, MMT, and gentamicin sulfate (GS) showed controlled, stimuli-responsive antibiotic release [43]. However, polylysine has not yet been explored in powder coatings.\u003c/p\u003e\n\u003cp\u003eThis study investigates the incorporation of \u0026epsilon;-PL into epoxy-based powder coatings both in its pristine form and intercalated into MMT, with or without aminododecanoic acid (ADA). The goal is to evaluate the effects on antimicrobial, aesthetic, and mechanical performance, offering a sustainable silver-free alternative for antimicrobial protection.\u003c/p\u003e"},{"header":"2. Experimental Part","content":"\u003cp\u003e\u003cem\u003e2.1. Preparation of antimicrobial agents (AA) and powder coatings\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAntimicrobial agents were prepared by intercalating \u0026epsilon;-polylysine (PLY), with or without aminododecanoic acid (ADA), into sodium montmorillonite (MMT). The modified clays were incorporated into epoxy-based powder coatings and applied under control conditions.\u003c/p\u003e\n\u003cp\u003eDetails on synthesis, formulation, application, and curing are provided in the Supporting Information (Sections S1\u0026ndash;S3).\u003c/p\u003e\n\u003cp\u003eTable. 1. Qualitative/quantitative composition of the powder coatings\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"615\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 25.487%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComponent/\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eSymbol of coating\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eepoxy resin, wt %\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6.49351%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eG-92, wt%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.92857%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ebenzoin\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7.46753%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eByk 368P\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ewt%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.9351%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY/MMT\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ewt%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19.1558%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY/MMT/ADA\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ewt%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 25.487%;\"\u003e\n \u003cp\u003eEP (reference sample)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e83,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6.49351%;\"\u003e\n \u003cp\u003e15,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.92857%;\"\u003e\n \u003cp\u003e0,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7.46753%;\"\u003e\n \u003cp\u003e1,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.9351%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19.1558%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 25.487%;\"\u003e\n \u003cp\u003ePLY\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e82,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6.49351%;\"\u003e\n \u003cp\u003e14,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.92857%;\"\u003e\n \u003cp\u003e0,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7.46753%;\"\u003e\n \u003cp\u003e1,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e2,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.9351%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19.1558%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 25.487%;\"\u003e\n \u003cp\u003ePLY/MMT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e82,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6.49351%;\"\u003e\n \u003cp\u003e14,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.92857%;\"\u003e\n \u003cp\u003e0,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7.46753%;\"\u003e\n \u003cp\u003e1,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.9351%;\"\u003e\n \u003cp\u003e2,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19.1558%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 25.487%;\"\u003e\n \u003cp\u003ePLY/MMT/ADA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e82,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6.49351%;\"\u003e\n \u003cp\u003e14,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.92857%;\"\u003e\n \u003cp\u003e0,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7.46753%;\"\u003e\n \u003cp\u003e1,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8.76623%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.9351%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19.1558%;\"\u003e\n \u003cp\u003e2,0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003cem\u003e2.4. Measurements\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eCharacterization included SEM, XRD, FTIR, TGA, DSC, DMA, SKP, profilometry, gloss, adhesion, hardness, and microbiological tests (EN ISO 22196).\u003c/p\u003e\n\u003cp\u003eFull descriptions are provided in the Supporting Information (Sections S4\u0026ndash;S6).\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003e\u003cem\u003e3.1. Antimicrobial agents\u0026rsquo; characterization\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePolylysine (PLY) was used to impart antibacterial properties to powder coatings, either in its pristine form or after immobilization in montmorillonite (MMT) (Fig. 1). For the latter, two approaches were studied: intercalation of PLY from aqueous solution, and co-intercalation with aminododecanoic acid (ADA).\u003c/p\u003e\n\u003cp\u003eAdding a second intercalant with a long alkyl chain, such as ADA, facilitates PLY intercalation. The 12-carbon chain penetrates the interlayer space of MMT, increasing the distance between the layers. This effect appears in the XRD pattern of ADA-intercalated MMT, where the (001) reflection shifts to lower 2\u0026theta; angles\u0026mdash;indicating an interlayer expansion from 12.8 \u0026Aring; (pristine MMT) to nearly 20 \u0026Aring;. Immobilizing polylysine in MMT may also reduce its leaching from the coating during prolonged moisture exposure.\u003c/p\u003e\n\u003cp\u003eThe PLY- and/or ADA-modified MMTs were characterized using elemental analysis, X-ray diffraction (XRD), and BET surface area measurements. Results are listed in Table 2 and shown in Fig. 2.\u003c/p\u003e\n\u003cp\u003eTable. 2. Characteristics of components used in the study\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"614\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.3355%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAA symbol\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11.0749%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eC [%]\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eH [%]\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eN [%]\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9.28339%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eC/N w/w\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eInterlayer distance d\u003csub\u003e001\u003c/sub\u003e \u0026Aring; (XRD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSpecific surface area m\u003csup\u003e2\u003c/sup\u003e/g (BET)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.3355%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11.0749%;\"\u003e\n \u003cp\u003e39.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e8.024\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e15.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.28339%;\"\u003e\n \u003cp\u003e2.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.3355%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMMT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11.0749%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.28339%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e12.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e29.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.3355%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eADA/MMT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11.0749%;\"\u003e\n \u003cp\u003e18.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e3.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e2.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.28339%;\"\u003e\n \u003cp\u003e8.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e19.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e12.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.3355%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY/MMT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11.0749%;\"\u003e\n \u003cp\u003e7.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e2.033\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e3.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.28339%;\"\u003e\n \u003cp\u003e2.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e13.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e20.19\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.3355%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY/MMT/ADA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 11.0749%;\"\u003e\n \u003cp\u003e7.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e2.167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10.7492%;\"\u003e\n \u003cp\u003e2.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 9.28339%;\"\u003e\n \u003cp\u003e2.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e14.0 (21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18.4039%;\"\u003e\n \u003cp\u003e21.91\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;Combustion elemental analysis revealed that both the carbon content and C/N weight ratio are significantly lower in PLY/MMT than in ADA/MMT, due to the higher carbon content of the long-chain amino acid. The co-intercalated PLY/MMT/ADA shows only a slight increase in these values compared to PLY/MMT but differs substantially from ADA/MMT.\u003c/p\u003e\n\u003cp\u003eGiven the similar BET surface areas and (001) reflection positions in the XRD spectra, polylysine appears to be the dominant intercalating species. A weak additional low-angle reflection at ~20 \u0026Aring; suggests that some long-chain amino acid molecules may also be partially incorporated between the MMT layers.\u003c/p\u003e\n\u003cp\u003eTo evaluate whether the newly developed antimicrobial components are thermally stable under the conditions of powder coating processing and curing, thermogravimetric analysis (TGA) was performed. The results are summarized in Table 3.\u003c/p\u003e\n\u003cp\u003eTable 3. TGA results of used\u0026nbsp;components\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"534\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAA symbol\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDecomposition temperature ranges\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e/ % wt. loss\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDTG max\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e\u003cstrong\u003etotal % wt. loss\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eat 700 \u0026ordm;C\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMMT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e25-180 / 10\u003c/p\u003e\n \u003cp\u003e200-700 / 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e76.5\u003c/p\u003e\n \u003cp\u003e639\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eADA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e180-260\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e380-500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e209\u003c/p\u003e\n \u003cp\u003e462\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMMT/ADA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e25-200 / 3\u003c/p\u003e\n \u003cp\u003e200-700 / 27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003cp\u003e260, 297, 354\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e25-180 / 8\u003c/p\u003e\n \u003cp\u003e240-560/ 83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e76\u003c/p\u003e\n \u003cp\u003e310,425,444\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e91\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY/MMT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e25-180 / 13\u003c/p\u003e\n \u003cp\u003e180-600 / 14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e57\u003c/p\u003e\n \u003cp\u003e330, 470, 559\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 26.9663%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePLY/MMT/ADA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30.1498%;\"\u003e\n \u003cp\u003e25-270\u003c/p\u003e\n \u003cp\u003e270-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.4757%;\"\u003e\n \u003cp\u003e50 /5\u003c/p\u003e\n \u003cp\u003e331, 436, 556\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23.4082%;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe first stage of thermal decomposition of the raw materials and intercalated montmorillonites involves desorption of water adsorbed in the aluminosilicate interlayers. Water content depends on hydrophobicity\u0026mdash;highest for PLY/MMT (13%) and lowest for MMT/ADA (3%). In sodium montmorillonite, the next mass loss occurs between 500\u0026ndash;700 \u0026deg;C, attributed to clay dehydroxylation [\u003csup\u003e1\u003c/sup\u003e].\u003c/p\u003e\n\u003cp\u003eTGA of polylysine shows two main decomposition steps: 180\u0026ndash;380 \u0026deg;C (65% mass loss) and above 380 \u0026deg;C (26%). Aminododecanoic acid also decomposes in two steps: the first at 180 \u0026deg;C (Hoffmann elimination of \u0026beta;-H) and the second at 400 \u0026deg;C, corresponding to degradation of the organic residue decomposes [\u003csup\u003e2\u003c/sup\u003e]. PLY leaves a higher char residue (9%), while ADA shows 99% total weight loss, likely due to its low molecular weight and high aliphatic carbon content.\u003c/p\u003e\n\u003cp\u003ePLY intercalation into MMT results in a shift of the DTG peaks to higher temperatures, indicating improved thermal stability. Mass loss is greater above 380 \u0026deg;C (10%) than in the 180\u0026ndash;380 \u0026deg;C range (4%). In contrast, ADA shows reduced decomposition temperatures after intercalation, consistent with Liu et al., who attributed this to the catalytic effect of montmorillonite\u0026rsquo;s solid acidity on ALA degradation [\u003csup\u003e3\u003c/sup\u003e].\u003c/p\u003e\n\u003cp\u003eThe co-intercalation product PLY/MMT/ADA displays thermal behavior similar to PLY/MMT but yields a higher char residue (80%) than ADA/MMT (70%) or PLY/MMT (73%).\u003c/p\u003e\n\u003cp\u003eThe powder coating process was conducted at 115 \u0026deg;C, with curing at 130 \u0026deg;C. TGA results confirm that only moisture is released within this range. Above 130 \u0026deg;C, the mass remains stable up to ~180 \u0026deg;C, confirming the thermal stability of the antimicrobial systems under typical powder coating conditions.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The chemical structure of the obtained antimicrobial agents was confirmed by FTIR spectra provided in the Supporting Information (Section S7). The FTIR spectra of PLY/MMT and PLY/MMT/ADA are dominated by bands of montmorillonite at about 1000 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, which is related to the stretching vibrations of the Si-O bonds, as well as by the weaker band at about 3620 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, which is attributed to stretching vibrations of O-H bonds (Figs. S7.1b and S7.1c) [\u003csup\u003e4\u003c/sup\u003e]\u003cstrong\u003e.\u0026nbsp;\u003c/strong\u003eThese FTIR spectra contain also additional peaks near 3230 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, 2935 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, 1670 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e and 1550 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, which are derived from polylysine (Fig. S7.1a) and correspond respectively to the vibrational modes of the amide group and protonated -NH\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e side chain groups stretching vibration [\u003csup\u003e5\u003c/sup\u003e,\u003csup\u003e6\u003c/sup\u003e]. This confirms the protonation of nitrogen atoms in polylysine, which enables interaction between -NH\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e groups and negatively charged sites of montmoryllonite (MMT). The presence of protonated ammonium groups is also a key factor influencing antibacterial properties of polylysine.\u003c/p\u003e\n\u003cp\u003eThe morphology of antimicrobial additives were investigated by SEM (Fig. 3).\u003c/p\u003e\n\u003cp\u003eAntimicrobial additives based polylysine were characterized by different morphology depending on the treatment used. Pure polylysine particles were characterized by a near-spherical shape and had a slightly developed surface. The size of the powder particles ranges from about 5-100 \u0026mu;m. Polylysine particles immobilized on sodium montmorillonite have a noticeably more developed surface and a size in the range of about 1-40 \u0026mu;m. Particles of polylysine powder immobilized on MMT modified with aminedodecanoic acid are characterized by a similar size to the unmodified variant, show a developed surface area and. Additionally, these particles tended to form agglomerates on the surface of larger powder particles.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2. Powder coatings characterisation\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePowder coatings were prepared with polylysine, either alone or intercalated on MMT, as well as co-intercalated with ADA. Intercalation aimed to enhance dispersibility of the modifier in the powder coating, improve compatibility with the polymer matrix, and increase washing resistance. Coatings were cured at 130\u0026deg;C for 10 min, during which epoxy groups from the resin reacted with a phenolic curing agent E011. The cross-linked coatings were tested for visual, mechanical, and antibacterial properties. Coatings free of defects such as orange peel, cratering, or pinholes were achieved. Their properties are detailed in Table 4.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 4. Specifications of coatings properties.\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"591\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 35.533%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eSymbol of coating\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 19.1201%;\"\u003e\n \u003cp\u003eEP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.044%;\"\u003e\n \u003cp\u003ePLY\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.3824%;\"\u003e\n \u003cp\u003ePLY/MMT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16.9205%;\"\u003e\n \u003cp\u003ePLY/MMT/ADA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eRoughness\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eEN ISO 12085\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.3824%;\"\u003e\n \u003cp\u003eR\u003csub\u003ea\u003c/sub\u003e, \u0026micro;m\u003c/p\u003e\n \u003cp\u003eR\u003csub\u003ez\u003c/sub\u003e, \u0026micro;m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e0.82\u0026plusmn;0.02\u003c/p\u003e\n \u003cp\u003e5.01\u0026plusmn;0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e0.21\u0026plusmn;0.02\u003c/p\u003e\n \u003cp\u003e1.38\u0026plusmn;0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e0.36\u0026plusmn;0.02\u003c/p\u003e\n \u003cp\u003e2.75\u0026plusmn;0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e0.18\u0026plusmn;0.03\u003c/p\u003e\n \u003cp\u003e0.95\u0026plusmn;0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eGloss for the angle of 60deg\u003c/p\u003e\n \u003cp\u003eEN ISO 2813\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003eGU\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e72.3\u0026plusmn;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e104.9\u0026plusmn;1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e74.2.1\u0026plusmn;0.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e99.8\u0026plusmn;2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eScratch resistance\u003c/p\u003e\n \u003cp\u003eEN ISO 1518\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003eg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eRelative hardness\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eEN ISO 1522\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e0.80\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e0.90\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e0.83\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e0.86\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eAdhesion to the steel\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eEN ISO 2409\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e0-best\u003c/p\u003e\n \u003cp\u003e5-worst\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eCupping\u003c/p\u003e\n \u003cp\u003eISO 1520\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e8.70\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e4.02\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e8.74\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e9.35\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eWater contact angle\u003c/p\u003e\n \u003cp\u003eEN 828\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003edeg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003e89.0\u0026plusmn;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e87.7\u0026plusmn;1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e89.1\u0026plusmn;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e88.2\u0026plusmn;1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eReduction of \u003cem\u003eE. coli\u003c/em\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eEN ISO 22196\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.3824%;\"\u003e\n \u003cp\u003eLog reduction\u003c/p\u003e\n \u003cp\u003e% reduction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003eRef. sample:\u003c/p\u003e\n \u003cp\u003elog total number of cells 4,32\u0026plusmn;0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e4.80\u0026plusmn;0.01\u003c/p\u003e\n \u003cp\u003e99.998\u0026plusmn;0.010\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e2.52\u0026plusmn;0.04\u003c/p\u003e\n \u003cp\u003e99.698\u0026plusmn;0.057\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e0.15\u0026plusmn;0.01\u003c/p\u003e\n \u003cp\u003e29.77\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 21.1506%;\"\u003e\n \u003cp\u003eReduction of \u003cem\u003eS. aureus\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eEN ISO 22196\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14.3824%;\"\u003e\n \u003cp\u003eLog reduction\u003c/p\u003e\n \u003cp\u003e% reduction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19.1201%;\"\u003e\n \u003cp\u003eRef. sample:\u003c/p\u003e\n \u003cp\u003elog total number of cells 4,77\u0026plusmn;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.044%;\"\u003e\n \u003cp\u003e2.57\u0026plusmn;0.03\u003c/p\u003e\n \u003cp\u003e99.733\u0026plusmn;0.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 14.3824%;\"\u003e\n \u003cp\u003e0.33\u0026plusmn;0.01\u003c/p\u003e\n \u003cp\u003e52.881\u0026plusmn;0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.9205%;\"\u003e\n \u003cp\u003e0.15\u0026plusmn;0.01\u003c/p\u003e\n \u003cp\u003e30.00\u0026plusmn;0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe surface coatings roughness was determined as average parameters R\u003csub\u003ea\u003c/sub\u003e and R\u003csub\u003ez\u003c/sub\u003e. The roughness values for all samples were characteristic for smooth coatings. However, roughness of reference sample (R\u003csub\u003ea\u0026nbsp;\u003c/sub\u003e= 0.82\u0026plusmn;0.02 \u0026micro;m, R\u003csub\u003ez\u0026nbsp;\u003c/sub\u003e= 5.01\u0026plusmn;0.16 \u0026micro;m) were\u0026nbsp;higher than modified coatings.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe addition of polylysine reduces the coating roughness, which indicates an increase of homogeneity. As a result of modification with polylysine intercalated on MMT, a slight increase in surface roughness was observed in comparison to PLY sample, which indicates a decrease of homogeneity in this coating resulting from the difference in interactions between the resin and MMT particles with a more hydrophilic structure. The addition of polylysine immobilized on MMT modified with aminodecanoic acid affects the reduction of roughness due to the presence of the hydrophobic ADA chain, which causes an increase in homogeneity with epoxy matrix.\u003c/p\u003e\n\u003cp\u003eIn addition to the roughness values determined by using a stylus profilometer (Table 4), complementary surface roughness measurements were performed using a laser scanning microscope (LSM) (Fig. 4). This technique enables high-resolution, three-dimensional visualization of the surface topography and provides numerical values for roughness parameters such as Ra and Rz. The results for selected coatings are summarized below:\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003ePLY: Ra = 0.680 \u0026micro;m, Rz = 9.32 \u0026micro;m\u003c/li\u003e\n \u003cli\u003ePLY/MMT: Ra = 2.932 \u0026micro;m, Rz = 42.35 \u0026micro;m\u003c/li\u003e\n \u003cli\u003ePLY/MMT/ADA: Ra = 2.579 \u0026micro;m, Rz = 43.91 \u0026micro;m\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThese values confirm the trends observed with stylus profilometry: coatings modified with nanofillers such as MMT and ADA exhibit higher surface roughness compared to the unmodified PLY formulation. This is attributed to the presence of dispersed filler particles on the surface, which increase topographical variations.\u003c/p\u003e\n\u003cp\u003eLaser scanning microscopy (LSM) surface analysis revealed that the unmodified coating (PLY) had the lowest roughness (Ra = 0.680 \u0026micro;m; Rz = 9.32 \u0026micro;m). In contrast, nanocomposites PLY/MMT and PLY/MMT/ADA showed significantly higher roughness, with Ra values of 2.932 \u0026micro;m and 2.579 \u0026micro;m and PLY/MMT/ADA (Ra = 2.579 \u0026micro;m; Rz = 43.91 \u0026micro;m) displayed significantly increased roughness. These results suggest that the incorporation of MMT and ADA leads to a more pronounced surface texture, likely due to particle agglomeration or protrusions, resulting in less uniform films that may affect barrier properties and adhesion. 3D LSM images support this by showing different surface features and filler distribution between the composites.\u003c/p\u003e\n\u003cp\u003eIn summary, LSM-based roughness analysis complements stylus profilometry by providing spatially resolved, microstructural information. The combination of both techniques offers a comprehensive understanding of the correlation between surface topography and coating performance.\u003c/p\u003e\n\u003cp\u003eThe gloss of the coatings depended on their roughness. Coatings with lower roughness had higher gloss values. All coatings demonstrated good scratch resistance. Samples containing PLY showed scratch resistance at the same level as the reference sample. For coatings with MMT, lower scratch resistance values were observed, which is due to the low hardness of MMT (1.5 on the Mohs scale). Adding polylysine resulted in an increase in relative hardness compared to the epoxy-based reference sample, likely because of their stiffer chains and additional stiffening hydrogen bonds. Furthermore, during the coating cross-linking process, the epoxy groups from the epoxy resin may react with the amino groups of polylysine, causing cross-linking and increasing hardness\u0026nbsp;[\u003csup\u003e7\u003c/sup\u003e]. For MMT-containing samples, hardness also increased compared to the reference, but was slightly lower than the PLY coating, due to the hard lamellar structure of MMT. Samples with polylysine are less resistant to cupping, possibly because of its linear structure affecting the tribological properties of the crosslinked epoxy matrix. MMT samples are more resistant to cupping thanks to the stronger bonds of Si-O (1096 kJ/mol) and Al-O (957 kJ/mol) in MMT, compared to bonds in the epoxy matrix like C-C (347 kJ/mol), C-H (415 kJ/mol), and C-O (360 kJ/mol), which increases this parameter [\u003csup\u003e8\u003c/sup\u003e]. Adhesion to the steel surface was high, thanks to polar functional groups such as secondary hydroxyls formed during the epoxy curing process with the polyphenol curing agent. These hydroxyl groups interact electrostatically with the steel substrate, boosting adhesion. In the PLY-containing sample, a decrease in contact angle was observed, reflecting its more hydrophilic nature.\u003c/p\u003e\n\u003cp\u003eThe presented data show that the sample containing polylysine has very high antibacterial activity against E. coli, with a reduction of 99.998%, but slightly lower activity against S. aureus at 99.733%. This suggests PLY is more effective against Gram-negative bacteria, likely due to differences in cell wall structure. When immobilized on MMT, PLY still effectively reduces E. coli, but has a much lower effect on S. aureus. Amino acid co-intercalation further decreases activity, resulting in about a 30% reduction for both bacterial strains.\u003c/p\u003e\n\u003cp\u003eThe effect of antimicrobial agents on the behavior of powder coatings during controlled heating was investigated using the DSC and DMA technique (Fig. 5 and Fig. 6). On the DSC curves recorded during the first heating of the samples, a glass transition with relaxation occurred and the glass transition temperature was determined, which for the EP reference sample was 102.3\u0026deg;C (Fig. 5a). For the samples containing 2 wt.%, the addition of the biocide compositions PLY/MMT and PLY/MMT/ADA (Fig. 5a) had no effect on the glass transition temperature, which was 102.6\u0026deg;C and 102.1\u0026deg;C, respectively. There was a clear effect of the addition of 2 wt.% polylysine (Fig. 5a) on lowering the glass transition temperature of the EP binder by 10.9\u0026deg;C relative to that of the reference sample. PLY which interacts with EP may be responsible for this condition. Chen et al. [\u003csup\u003e9\u003c/sup\u003e] described that PLY interacts with C-O groups in EP via NH groups. The authors describe that this effect is visible in the glass transition temperature value. Shukla et al. [\u003csup\u003e10\u003c/sup\u003e] reported that the glass transition temperature of microbial crystalline poly(\u0026epsilon;-L-lysine) is 88\u0026deg;C. It should be noted that lysine and lysine-based (amino-functionalized polyester) polyesters exhibit tunable thermal properties i.e. glass transition, melting point, which increases with increasing M\u003csub\u003en\u003c/sub\u003e of the amino-functionalized polyester.\u003c/p\u003e\n\u003cp\u003eThe glass transition temperature of the reference sample, determined from the DSC curve recorded at the second heating stage, was 105.5\u0026deg;C compared to 106.5\u0026deg;C for the PLY/MMT sample and 105.2\u0026deg;C for the PLY/MMT/ADA sample (Fig. 5b). The slight differences in the determined values are due to the removal of thermal history and stress in the coating samples tested. The sample containing 2 wt.% PLY had a lower glass transition temperature value of 97.9\u0026deg;C. The difference in Tg value between the 2 wt.% PLY sample and the reference sample decreased in the second heating because of the ordering of the binder structure of the PLY-containing sample.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The dynamic mechanical analysis showed that the glass transition was the predominant transition recorded during the tests performed. The value of the peak of the mechanical loss factor (tan \u0026delta;) was taken as the glass transition temperature. For the reference sample, the glass transition was determined at 107.3\u0026deg;C Fig. 6a). Very similar values were obtained for the MMT/PLY and MMT/PLY/ADA samples at 107.7\u0026deg;C and 108.1\u0026deg;C respectively (Figs. 6c and 5d). The lowest glass transition temperature was 91.7\u0026deg;C for the sample containing 2 wt% PLY (Fig. 6b). This sample had the lowest intensity of the tan \u0026delta; peak, indicating good attenuation/damping properties. The other samples had similar tan \u0026delta; intensities. The analysis of the storage modulus values is also significant, from which it can be concluded that the samples underwent relaxation and intramolecular reorganization of the EP matrix at an early stage of the test, followed by vitrification, and that at a higher temperature the samples were in an elastic state, as evidenced by the low storage modulus value. The influence of MMT and ADA in the MMT/PLY/ADA sample is also evident, with the MMT/PLY/ADA sample showing the highest storage modulus of the samples tested (approximately 700 MPa versus 550 MPa for the reference sample, 600 MPa for PLY and 450 MPa for MMT/PLY), indicating the highest energy storage capacity of the samples tested and the higher stiffness of the sample in the dynamic shear deformation mode.\u003c/p\u003e\n\u003cp\u003eTo investigate the elemental distribution and homogeneity of antimicrobial coatings, SEM/EDS mapping and quantification were performed for three formulations: PLY, PLY/MMT, and PLY/MMT/ADA.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5.\u003c/strong\u003e Elemental composition (in weight %) of powder coatings containing polylysine (PLY), polylysine immobilized in montmorillonite (PLY/MMT), and polylysine immobilized in montmorillonite modified with aminododecanoic acid (PLY/MMT/ADA), as determined by EDS spectroscopy.\u0026nbsp;\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"604\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eElement\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeight %_ PLY\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeight %_ PLY/MMT\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeight %_PLY/MMT/ADA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e21,81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e75,54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e23,52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eOK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e18,36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e3,95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e28,74\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eFeI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e1,34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e0,33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e1,88\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eAlK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e2,05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e0,03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e9,43\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eSiK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e0,33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e0,29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e23,49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eAuM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e20,98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e19,84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e10,45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eNK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e0,27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e0,08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eKK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e0,26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eNaK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e0,15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eBaI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e29,08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eSK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e5,77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13.0579%;\"\u003e\n \u003cp\u003eMgK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 26.9421%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.4298%;\"\u003e\n \u003cp\u003e0,01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31.5702%;\"\u003e\n \u003cp\u003e1,47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe elemental composition and distribution of the antimicrobial powder coatings were evaluated by EDS spectroscopy and are summarized in Table 5.\u003c/p\u003e\n\u003cp\u003eFor the PLY system, the EDS spectrum revealed a high carbon content (~74.6 wt%) along with notable amounts of oxygen (11.8 wt%), nitrogen (2.2 wt%), and sulfur (5.4 wt%). The presence of nitrogen and sulfur is consistent with the chemical structure of polylysine and the epoxy resin. The elemental mapping indicates a homogeneous distribution of components, suggesting uniform film formation. Minor traces of elements such as Na, Al, and Si are likely attributable to the substrate or incidental contamination.\u003c/p\u003e\n\u003cp\u003eIn the PLY/MMT formulation, the successful incorporation of montmorillonite is evidenced by a significant increase in silicon (13.4 wt%) and aluminum (2.6 wt%), while the carbon content slightly decreases (~75.6 wt%) due to the inorganic nature of the filler. Oxygen content is elevated, reflecting contributions from the silicate framework. Mapping data reveal distinguishable montmorillonite agglomerates with locally increased density, yet overall dispersion remains relatively even. The consistent nitrogen signal suggests that polylysine remains well distributed throughout the matrix.\u003c/p\u003e\n\u003cp\u003eFor the PLY/MMT/ADA system, the oxygen (21.6 wt%) and nitrogen (4.2 wt%) contents increase further, reflecting the additional functional groups introduced by aminododecanoic acid (ADA). The carbon content drops to ~31.5 wt%, while Si and Al levels remain comparable to the PLY/MMT sample, indicating a stable montmorillonite fraction. The mapping shows localized clusters that may correspond to ADA-rich domains or phase-separated regions. These inhomogeneities are also visible as distinct contrast variations in SEM images. Such segregation may influence both the electrochemical surface behavior (as evidenced by SKP measurements) and the availability of antimicrobial agents [54,55].\u003c/p\u003e\n\u003cp\u003eThe surface potential distribution of antimicrobial powder coatings was investigated using SKP measurements to evaluate the influence of polylysine and its combinations with montmorillonite (MM) and aminododecanoic acid (ADA) on electron transfer characteristics at the surface (Fig. 8).\u003c/p\u003e\n\u003cp\u003eFor the PLY system, the surface potential ranged from approximately 0.46 V to 0.56 V, with a slight positive gradient across the scanned area (Fig. 8a). This indicates a mildly electron-enriched surface, which may promote initial oxygen reduction, followed by the formation of a positively charged electrical double layer that limits further redox activity.\u003c/p\u003e\n\u003cp\u003eIn contrast, the PLY/MMT sample exhibited a clear negative slope in surface potential, decreasing from ~1.3 V to 1.0 V across the surface (Fig. 8b). This behavior suggests that the interaction between polylysine and the montmorillonite matrix induces electron depletion and enhanced band bending, which can reduce surface reactivity, particularly toward oxygen adsorption and reduction.\u003c/p\u003e\n\u003cp\u003eThe most pronounced behavior was observed in the PLY/MMT/ADA sample (Fig. 8c). Here, the surface potential exhibited a sharp gradient, ranging from above +12 V to below +2 V, with localized charge accumulation particularly evident in the lower-left region of the map. This extreme potential inhomogeneity may result from phase separation or the formation of microdomains. The pronounced lateral potential differences and steep voltage drops indicate strong spatial variation in electron distribution, likely leading to reduced electron mobility. Such effects may contribute to the diminished antimicrobial performance observed in this formulation.\u003c/p\u003e\n\u003cp\u003eThese findings highlight how the surface electrochemical landscape of antimicrobial powder coatings can be tuned by additive combination. While pure polylysine enhances surface electron availability, its combination with layered fillers and co-additives introduces structural and electronic complexity that may impair surface reactivity.\u003c/p\u003e\n\u003cp\u003eThe combination of SKP results with previously shown EDS data suggests a correlation between chemical homogeneity and surface potential stability:\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003ePLY: homogeneous structure, stable surface potential\u003c/li\u003e\n \u003cli\u003ePLY/MMT: moderate agglomeration, downward potential trend\u003c/li\u003e\n \u003cli\u003ePLY/MMT/ADA: visible inhomogeneities, sharp potential gradients and localized charge accumulation\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThese findings underline that while additive combinations like MMT and ADA may enhance certain physical properties, they can lead to microphase separation, affecting charge transport and possibly reducing antimicrobial efficiency.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cem\u003e3.3. Washing resistance of antibacterial additives\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eTo initially determine the resistance of powder coatings to the leaching of antibacterial additives, we investigated the changes in water conductivity when in contact with the cured coating over time. Conductometric analysis of the washing resistance of powder coatings containing PLY, PLY/MMT, and PLY/MMT/ADA\u0026nbsp;was\u0026nbsp;provided in the Supporting Information (Section S8). In the case of coatings containing polylysine alone, a significant increase in conductivity values is observed after 5 to 7 days, indicating the gradual dissolution of the polymer containing ionic groups.\u003c/p\u003e\n\u003cp\u003eImmobilization on MMT significantly reduces polylysine leaching for three weeks, followed by a rise in water conductivity. In contrast, the co-intercalation product PLY/MMT/ADA shows no increase in conductivity compared to the coating without biocide, even after 25 days, emphasizing the stabilizing role of amino acid modification\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cem\u003e3.4. Mechanism of antimicrobial action\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe antimicrobial activity of powder coatings containing polylysine and its combinations with montmorillonite (MM) and amino dodecanoic acid (ADA) can be explained by a combination of physicochemical interactions at the coating\u0026ndash;microorganism interface.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to the studies of Nigmatullin et al., the intercalation compounds of montmorillonite with cationic polymers exhibit two modes of antimicrobial activity: the migration of the biocide to the surface and contact-killing of bacteria through interaction with immobilized cationic species on the surface. The diffusion of the biocide is rather slow, and the contact mechanism plays the dominant role [56]\u003cstrong\u003e.\u0026nbsp;\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Based on previous studies and the newly obtained SKP and EDS data, three main mechanisms are considered (Fig. 9):\u003c/p\u003e\n\u003cp\u003e1. Electrostatic attraction and surface charge modulation:\u003c/p\u003e\n\u003cp\u003eBacterial cell membranes are usually negatively charged. Coatings with cationic agents like polylysine create a positive surface, increasing attraction of microbial cells. SKP measurements of the PLY system confirm a relatively uniform, slightly positive surface, promoting bacterial adhesion and charge interactions that may destabilize the membrane and trigger antimicrobial activity.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn contrast, incorporating montmorillonite (PLY/MMT) alters surface potential. Clay layered structure has negative charges, causing electron depletion and lowering surface potential. This redistributes charge, reducing electrostatic attraction between the coating and bacteria, impairing microbial interaction.\u003c/p\u003e\n\u003cp\u003e(2) Ionic imbalance and membrane damage:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn the PLY/MMT/ADA system, SKP contour plots show strong potential gradients and areas of high surface charge. These may create local electric fields disrupting osmotic balance across bacterial membranes, causing ion and water leakage, membrane rupture, and cell death. This is supported by inhomogeneity in elemental distribution (seen in EDS mapping), indicating partial phase separation of ADA domains.\u003c/p\u003e\n\u003cp\u003e(3) Inhibition of redox processes and potential oxidative stress:\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Electron transfer reactions, especially oxygen reduction on the coating surface, are affected by surface potential. In PLY coating, a moderate positive potential might permit limited redox activity. However, the sharp potential drop in PLY/MMT/ADA indicates an electron-depleted surface state, making oxygen reduction unlikely. This surface may hinder electron transfer processes, potentially interfering with microbial respiration processes. Localized high-potential zones may also generate reactive oxygen species (ROS), damage cells and disrupting metabolism.\u003c/p\u003e\n\u003cp\u003eIn summary, the antimicrobial effectiveness of polylysine coatings depends on the additive\u0026apos;s chemistry, surface potential, and distribution. A homogeneous, moderately positive potential, as observed for PLY, seems most favorable for electrostatic interaction and antimicrobial activity. Composites with MMT and ADA may cause inhomogeneity, reducing biocidal performance.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, silver-free antimicrobial powder coatings based on epoxy resin and the cationic biopolymer polylysine were successfully developed and characterized. Polylysine was applied in three different forms: as a pure additive, intercalated in montmorillonite (PLY/MMT), and co-intercalated with aminododecanoic acid (PLY/MMT/ADA). The aim was to enhance antimicrobial efficacy, reduce leaching, and improve compatibility within the coating matrix.\u003c/p\u003e\n\u003cp\u003eComprehensive physicochemical characterization\u0026mdash;including FTIR, XRD, TGA, DSC, DMA, SEM/EDS, and SKP\u0026mdash;demonstrated that the structure and distribution of the additives significantly influence thermal stability, mechanical properties, and surface electrochemical behavior.\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003ePure polylysine improved coating homogeneity and provided a stable, moderately positive surface potential, favorable for electrostatic interaction with bacterial membranes.\u003c/li\u003e\n \u003cli\u003eThe addition of montmorillonite increased thermal resistance and hardness but introduced surface potential gradients and reduced antimicrobial performance.\u003c/li\u003e\n \u003cli\u003eCo-intercalation with ADA improved leaching resistance and mechanical reinforcement yet led to charge inhomogeneity that may interfere with biological activity.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe results suggest that antimicrobial effectiveness may be influenced not only by the chemical composition of the additive but also by its electrochemical surface distribution under the given test conditions. Coatings with uniform cationic groups and stable surface potentials\u0026mdash;like the system with only PLY\u0026mdash;showed the highest antibacterial activity among the tested systems under laboratory conditions. Using polylysine, a biodegradable and renewable biopolymer, supports the development of sustainable biomaterials for antimicrobial applications. While the coatings demonstrated promising antimicrobial and mechanical properties in controlled laboratory settings, the study does not include long-term durability tests, environmental aging, or resistance against a broader spectrum of microorganisms. These aspects should be addressed in future work to assess real-word applicability and stability of the systems. Furthermore, eliminating silver may contribute to improved resource efficiency in designing antimicrobial coatings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the AiF and the NCBR within the CORNET programme (Project No. 363 EN; 01IF00363C, acronym: MicroSafeCoatings \u0026ndash; Novel antimicrobial protection in powder coatings for composite materials), and by the Ministry of Science and Higher Education of the Republic of Poland under the programme \u0026ldquo;Regional Excellence Initiative\u0026rdquo;, grant number RCD.RB.24.002.01.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u0026nbsp;\u003c/strong\u003eThe authors would like to thank Sarzyna Chemie, Allnex and BYKChemie for sending free samples of raw materials.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article and its supplementary information files. Additional data is available from the corresponding author on reasonable request.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eA.M. Pagtalunan, F.C. Sumera, M.T. Conato, Synthesis and characterization of 12-aminolauric acid-modified montmorillonite for catalytic application, AIP Conf. Proc. 1958 (2018) 020021. https://doi.org/10.1063/1.5034552.\u003c/li\u003e\n \u003cli\u003eJ. Zhu, A.B. Morgan, F.J. Lamelas, C.A. Wilkie, Fire Properties of Polystyrene−Clay Nanocomposites, Chem. Mater. 13 (2001) 3774-3780. https://pubs.acs.org/doi/10.1021/cm000984r.\u003c/li\u003e\n \u003cli\u003eH. Liu, P. Yuan, D. Liu, et al., Effects of solid acidity of clay minerals on the thermal decomposition of 12-aminolauric acid, J. Therm. Anal. Calorim. 114 (2013) 125–130. https://doi.org/10.1007/s10973-012-2887-0.\u003c/li\u003e\n \u003cli\u003eK. Kelar, B. Jurkowski, K. Mencel, Montmorylonit wyodrębniany z bentonitu — modyfikacja i możliwości wykorzystania w polimeryzacji anionowej ɛ-kaprolaktamu do otrzymywania nanokompozytów, Polimery 50 (2005), 449-454.\u003c/li\u003e\n \u003cli\u003eM. Rozenberg, G. Shoham, FTIR spectra of solid poly-L-lysine in the stretching NH mode range, Biophysical Chemistry 125 (2007) 166–171. https://doi.org/10.1016/j.bpc.2006.07.008.\u003c/li\u003e\n \u003cli\u003eS. K. Tama, J. Dusseaultb, S. Polizu, M. Me´nard, J.-P. Halle´, Y. L’Hocine Yahia, Physicochemical model of alginate–poly-L-lysine microcapsules defined at the micrometric/nanometric scale using ATR-FTIR, XPS, and ToF-SIM, Biomaterials 26 (2005) 6950–6961. doi: 10.1016/j.biomaterials.2005.05.007.\u003c/li\u003e\n \u003cli\u003eJ. Ostrowska-Czubenko, M. Pieróg, M. Gierszewska, Modification of chitosan – a concise overview, Wiadomości chemiczne 70 (2016) 657-679.\u003c/li\u003e\n \u003cli\u003eZ. Zhang, X. Song, Nanoscale crack propagation in clay with water adsorption through reactive MD modeling, The International Journal for Numerical and Analytical Methods in Geomechanics 47 (2023) 1103-1133. https://doi.org/10.1002/nag.3507.\u003c/li\u003e\n \u003cli\u003eX. Chen, H. Lai, C. Xiao, H. Tian, X. Chen, Y. Tao, X. Wang, New bio-renewable polyester with rich side amino groups from L-lysine via controlled ring-opening polymerization, Polymer Chemistry 5 (2014) 6495. DOI: 10.1039/c4py00930d\u003c/li\u003e\n \u003cli\u003eS.C. Shukla, A. Singh, A.K. Pandey, A. Mishra, Review on production and medical appications of ε-polylisine, Biochemical Engineering Journal 65 (2012) 70-81. DOI: 10.1016/j.bej.2012.04.001.\u003c/li\u003e\n \u003cli\u003eN. Kitadai, T. Yokoyama, S. Nakashima, In situ ATR-IR investigation of L-lysine adsorption on montmorillonite, Geochimica et Cosmochimica Acta 73 (2009) (13, Supplement), A687. https://doi.org/10.1016/j.jcis.2009.06.061.\u003c/li\u003e\n \u003cli\u003eC. Boahen, S. Wiafe, F. Owusu, L. Bian, Adsorption of heavy metals from mine wastewater using amino-acid modified Montmorillonite, Geochimica et Cosmochimica Acta 73 (2023) (13, Supplement) A687. https://doi.org/10.1080/27658511.2022.2152590.\u003c/li\u003e\n \u003cli\u003eR. Nigmatullin, F. Gao \u0026amp; V. Konovalova, Polymer-layered silicate nanocomposites in the design of antimicrobial materials. J Mater Sci 43, 5728–5733 (2008). https://doi.org/10.1007/s10853-008-2879-4\u003c/li\u003e\n\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":"polylysine, montmoryllonite, antimicrobial properties, epoxy coatings, powder coatings","lastPublishedDoi":"10.21203/rs.3.rs-7099997/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7099997/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this work, silver-free low-temperature curing epoxy powder coatings with antimicrobial properties were developed. To achieve this, the cationic biopolymer ε-polylysine (PLY) in its protonated form was used, along with intercalation products of PLY and co-intercalation products of PLY and aminododecanoic acid (ADA) in montmorillonite (MMT), as environmentally friendly alternative. The powder coatings were formulated using epoxy resin and a highly reactive phenolic curing agent. The resulting coatings were characterized in terms of surface roughness, gloss, scratch resistance, hardness, adhesion to steel, water contact angle, and antimicrobial resistance. A mechanism of antimicrobial activity was proposed.\u003c/p\u003e","manuscriptTitle":"Antimicrobial activity of silver free powder coatings based on biocomponents","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-04 22:27:58","doi":"10.21203/rs.3.rs-7099997/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-14T07:29:03+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-12T15:42:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-26T12:46:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"305034131600208672998913358296735386190","date":"2025-09-21T20:48:30+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"38656236984738775496272567970646570649","date":"2025-09-17T16:56:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"161627141791390931102443964783464252220","date":"2025-08-18T01:44:57+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-30T17:23:26+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-30T17:18:46+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-30T08:45:03+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-28T09:11:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-07-28T09:08:11+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":"4cecd753-d00a-485d-8966-c3a6ab59442a","owner":[],"postedDate":"August 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":52545523,"name":"Physical sciences/Chemistry"},{"id":52545524,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-12-08T16:00:37+00:00","versionOfRecord":{"articleIdentity":"rs-7099997","link":"https://doi.org/10.1038/s41598-025-30166-3","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-12-02 15:57:27","publishedOnDateReadable":"December 2nd, 2025"},"versionCreatedAt":"2025-08-04 22:27:58","video":"","vorDoi":"10.1038/s41598-025-30166-3","vorDoiUrl":"https://doi.org/10.1038/s41598-025-30166-3","workflowStages":[]},"version":"v1","identity":"rs-7099997","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7099997","identity":"rs-7099997","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}