97 lines
33 KiB
JSON
97 lines
33 KiB
JSON
[
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{
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"id": 1,
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"chunk": "# Synthesis of acrylate-based UV/thermal dual-cure coatings for antifogging \n\nBolong Yao, Haiping Zhao, Likui Wang, Yun Liu, Chunsen Zheng, Hongping Li, Changqing Sun \n\n$\\circleddash$ American Coatings Association 2017 \n\nAbstract A dual-cure hydrophilic acrylate polymer was synthesized via radical polymerization with acrylic acid (AA), isophorone diisocyanate (IPDI), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), hydroxyethyl acrylate (HEA), and 3-(trimethoxysilyl)propyl-2-methyl-2-methacrylate (MPS) as monomers, then used as prepolymer for antifog coating with tetraethylorthosilicate (TEOS) as a novel crosslinker. The prepolymer was mixed with crosslinking agent and photoinitiator to form coating formulas. The coating was characterized by nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR) spectroscopy, and contact angle measurements. The results indicated that the dosage of AMPS and TEOS had great influence on the antifog performance. With an increasing TEOS amount, the hardness, adhesion, water resistance, impact resistance, and thermal stability of the films were improved, at the expense of transparency; with increasing dosage of AMPS, the hydrophilicity of the film increased at the expense of water resistance. Optimum coating properties could be obtained when the amount of AMPS was $7\\%$ and that of TEOS was $5.5\\%$ . Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that some $\\mathrm{SiO}_{2}$ microspheres were formed and microphase separation occurred between the macromolecular segments, yielding the excellent coating properties. \n\nKeywords TEOS, Antifogging, Dual cure, Acrylate",
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"category": " Abstract"
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},
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"id": 2,
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"chunk": "# Introduction \n\nTransparent substrates (such as glass) play an important role in daily life.1–4 Due to the high surface energy, condensation of droplets occurs when the temperature of the substrate surface is below the ambient water vapor dew point. These droplets lead to light refraction and scattering, causing transparent materials to become hazy, resulting in many problems and even causing serious harm.5 At present, there are two main methods to solve this problem: electric heating and antifog coating.6 Although the former method is effective, inconvenience and energy consumption limit its wide application. According to antifogging theory, two types of coatings have been researched: superhydrophobic and superhydrophilic.6 Superhydrophobic coatings mainly utilize the gravity of droplets to allow dew condensation to tumble down to achieve the antifogging effect.7–11 However, efficiency remains a major problem, and poor adhesion and mechanical properties such as hardness and scratch resistance also limit wide application of this method. These disadvantages can be overcome more easily when using superhydrophilic coatings, where water droplets on the surface of such coatings rapidly spread into a water film that does not scatter light.12–15 In this case, if dew condensation occurs, the surface can still remain optically clear. Rubner’s group16 adopted a layered self-assembly method to deposit $\\mathrm{SiO}_{2}^{-}$ nanoparticles and polyelectrolyte alternately to form a superhydrophilic porous film. The contact angle was less than $5^{\\circ}$ , with excellent antifogging performance. Also, Zoromba et al.17 developed an ultraviolet (UV)-curable urethane acrylate antifog coating. However, the majority of inorganic nanoparticles require complex preparation processes and they are difficult to coat, usually requiring sintering,18 while it is difficult to obtain a balance between hydrophilicity and water resistance when using organic polymers. The hydrophilicity of a surface mainly relies on various strongly hydrophilic groups, such as hydroxyl, carboxyl, and sulfonic acid.19 On such surfaces, water can penetrate and swell the film. \n\nIn this work, acrylic ester was used as the main chain because of its good transparency. Hydrophilic monomer 2-acrylamide-2-methylpropane sulfonic acid (AMPS) was introduced to enhance the hydrophilicity of the film. The main chain of acrylic resin was modified with 3-(trimethoxysilyl)propyl-2-methyl-2- methacrylate (MPS), and tetraethylorthosilicate (TEOS) was used as a novel curing agent. The hydroxyl groups from MPS and TEOS, respectively, undergo a dehydration condensation reaction to generate a large number of Si–O–Si bonds20,21 under alkaline conditions. Because Si–O–Si bonds easily migrate to the coating surface during curing, a dense Si–O–Si network structure can form on the surface, giving the film excellent water resistance and mechanical properties. The film is ultimately cured by adding a photoinitiator and reactive diluents through the double bonds introduced into the main chain from halfblocked polyurethane. The other advantage of this approach is that use of tetraethylorthosilicate (TEOS) introduces a large number of hydroxyl groups. The formed $_{\\mathrm{Si-O-Si}}$ bonds with low surface tension bring the hydroxyl groups to the coating surface. This design ensures hydrophilicity and also imparts the coating with excellent mechanical properties and water resistance. Contact angle measurements, atomic force microscopy (AFM), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were applied to study the properties of films with different TEOS contents.",
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"category": " Introduction"
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},
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"id": 3,
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"chunk": "# Experimental",
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"category": " Materials and methods"
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},
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"id": 4,
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"chunk": "# Materials \n\nIsophorone diisocyanate (IPDI) was supplied by Bayer Co. Ltd. (Germany). 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) was purchased from SongChuan Industrial Additives Co. Ltd. (ShanDong, China). Hydroxyethyl acrylate (HEA) and 3-(trimethoxysilyl)propyl-2-methyl-2-methacrylate (MPS) were supplied by Sigma-Aldrich Co. Ltd. (Shanghai, China). Trimethylol propane triacrylate (15EO-TMPTA), azobisisobutyronitrile (AIBN), acrylic acid (AA), leveling agent (3288), and tetraethylorthosilicate (TEOS) were purchased from Aladdin Reagent Co. Ltd. (Shanghai, China). Dibutyltin dilaurate (DBTDL), 4-methoxyphenol (MEHQ), $N\\mathrm{,}N$ -dimethylformamide (DMF), photoinitiator (1173), ammonia, acetone (ACE), deuterated dimethyl sulfoxide (DMSO), ethanol, anhydrous methanol, and isopropanol were all supplied by Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China).",
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"category": " Materials and methods"
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},
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"id": 5,
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"chunk": "# Synthesis of prepolymer \n\nAA and HEA had been pretreated to remove polymerization inhibitor. A series of acrylate copolymers (PAAMH) were synthesized via free-radical copolymerization. A mixture of AA, AMPS, HEA, MPS, and DMF was added into a dried $250\\mathrm{-mL}$ four-necked flask equipped with mechanical stirrer, condenser, ${\\bf N}_{2}$ catheters, and pressure-equalizing dropping funnel. The mixture was stirred at room temperature under ${\\bf N}_{2}$ protection and gradually heated to $80^{\\circ}\\mathrm{C}$ . AIBN $3\\%$ of total monomer weight) was dissolved in a small amount of DMF, half of which was then added into the flask dropwise via the constant-pressure dropping funnel for $^{1\\mathrm{~h~}}$ at $80^{\\circ}\\mathrm{C}$ , and reacted for another $\\Bar{3}\\Bar{\\mathbf{h}}$ at $80^{\\circ}\\mathrm{C}$ . The remaining initiator was then added to the flask at the same dripping speed, and reacted for another $^{3\\mathrm{~h~}}$ . \n\nNucleophilic addition of IPDI and HEA was employed to prepare an isocyanate-containing unsaturated monomer, IPHE. A mixture of IPDI, HEA, MEHQ, ACE, and DBTDL was added into a dried $250\\mathrm{-mL}$ four-necked flask equipped with mechanical stirrer, condenser, ${\\bf N}_{2}$ catheters, and pressure-equalizing dropping funnel, then gradually heated to $55^{\\circ}\\mathrm{C}$ and allowed to react for $2\\mathrm{~h~}$ . The isocyanate (NCO) content was monitored during the reaction using the standard dibutylamine backtitration method. Upon reaching the theoretical NCO value, the product was cooled to room temperature, transferred to another pressureequalizing dropping funnel, then added dropwise to the PAAMH. At the same time, additional catalyst DBTDL was added and reacted at $80^{\\circ}\\mathrm{C}$ for about $^{3\\mathrm{~h~}}$ until the NCO content reached another theoretical value. Reaction completion was confirmed by disappearance of the FTIR absorption peak at $22\\dot{7}0~\\mathrm{cm}^{-1}$ corresponding to stretching vibration of NCO group. During the above process, acetone was added to adjust the viscosity of the IPHE prepolymer. Finally, the acetone was removed to afford PAAMH-IH with $30~\\mathrm{wt\\%}$ solid content. The whole synthetic route is shown in Fig. 1. The compositions of all formulas used are presented in Table 1.",
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"category": " Materials and methods"
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},
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"id": 6,
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"chunk": "# Preparation of antifog coatings \n\nPAAMH-IH was mixed with $3{\\mathrm{-}}4\\ \\mathrm{wt}\\%$ photoinitiator (Irgacure 1173), $0.3\\ \\mathrm{wt\\%}$ leveling agent 3288, and $25\\ \\mathrm{wt\\%}$ reactive diluents 15EO-TMPTA, and a certain amount of TEOS was introduced, as presented in Table 2. We chose 15EO-TMPTA as the reactive diluents to increase the double-bond content. The $\\mathrm{pH}$ value was adjusted to ${\\sim}13$ using aqueous ammonia (concentration ${\\sim}25\\%$ ), followed by quick stirring at room temperature. The solution was then coated on clean glass slides by dipping, and was then slowly dried at $50^{\\circ}\\mathrm{C}$ for $5\\mathrm{~h~}$ . The resulting films were heated in an oven at $70^{\\circ}\\mathrm{C}$ for another $2\\dot{\\mathrm{~h~}}$ . Finally, the films were irradiated using a 1200-W UV $(200-400~\\mathrm{nm})$ ) lamp for 30 s at room temperature. \n\n \nFig. 1: Synthesis and curing process of PAAMH-IH \n\nTable 1: Components of PAAMH resin \n\n\n<html><body><table><tr><td rowspan=\"2\">Sample</td><td colspan=\"6\">Content (g)</td><td rowspan=\"2\">W(AMPS) (%)℃</td></tr><tr><td>AA</td><td>HEAa</td><td>AMPS</td><td>MPS</td><td>HEAb</td><td>IPDI</td></tr><tr><td>PAAMH-IH-2%</td><td>10.00</td><td>6.00</td><td>0.72</td><td>2.00</td><td>6.00</td><td>11.50</td><td>2%</td></tr><tr><td>PAAMH-IH-4%</td><td>10.00</td><td>6.00</td><td>1.48</td><td>2.00</td><td>6.00</td><td>11.50</td><td>4%</td></tr><tr><td>PAAMH-IH-6%</td><td>10.00</td><td>6.00</td><td>2.26</td><td>2.00</td><td>6.00</td><td>11.50</td><td>6%</td></tr><tr><td>PAAMH-IH-8%</td><td>10.00</td><td>6.00</td><td>3.09</td><td>2.00</td><td>6.00</td><td>11.50</td><td>8%</td></tr><tr><td>PAAMH-IH-10%</td><td>10.00</td><td>6.00</td><td>3.94</td><td>2.00</td><td>6.00</td><td>11.50</td><td>10%</td></tr></table></body></html>\n\na Content of HEA on main chains; b Content of HEA on side chains; c Percentage of AMPS in total monomers \n\nTable 2: Components of PAAMH-IH resin \n\n\n<html><body><table><tr><td rowspan=\"2\">Sample</td><td colspan=\"5\">Content (g)</td><td rowspan=\"2\">W(TEOS) (%)</td></tr><tr><td>PAAMH-IH</td><td>TEOS</td><td>Ammonia</td><td>15EO-TMPTA</td><td>1173</td></tr><tr><td>PAAMH-IH-a</td><td>1.00</td><td>0.02</td><td>0.04</td><td>0.02</td><td>0.03</td><td>1.83%</td></tr><tr><td>PAAMH-IH-b</td><td>1.00</td><td>0.04</td><td>0.04</td><td>0.02</td><td>0.03</td><td>3.67%</td></tr><tr><td>PAAMH-IH-c</td><td>1.00</td><td>0.06</td><td>0.04</td><td>0.02</td><td>0.03</td><td>5.50%</td></tr><tr><td>PAAMH-IH-d</td><td>1.00</td><td>0.08</td><td>0.04</td><td>0.02</td><td>0.03</td><td>7.34%</td></tr><tr><td>PAAMH-IH-e</td><td>1.00</td><td>0.10</td><td>0.04</td><td>0.02</td><td>0.03</td><td>9.17%</td></tr></table></body></html>",
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"category": " Materials and methods"
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},
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"id": 7,
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"chunk": "# Characterization \n\nA Fourier-transform infrared spectrophotometer (FTLA2000-104, ABB Bomem of Canada) was used to confirm the chemical structure of IPHE, PAAMH, and PAAMH-IH. Purified product was dissolved in deuterated DMSO with tetramethylsilane (TMS) as internal standard. Then, $^1\\mathrm{H}$ and $^{13}\\mathrm{C}$ NMR spectra were recorded using a Bruker $500~\\mathrm{MHz}$ NMR (Avance III) to confirm the structure of PAAMH. Scanning electron microscopy (SEM, S4800, Hitachi) and atomic force microscopy (AFM, MultiMode 8, Bruker) were used to investigate the coating morphology. Samples were diluted to $15\\ \\mathrm{wt\\%}$ solid content with DMF, dripped onto a silicon wafer, and cured. The water resistance of the film was measured with reference to GB/T 1733- 1993 ‘‘determination of resistance to water of films.’’ Film hardness was measured with reference to GB/T 6739-2006 ‘‘paint and varnish pencil method to determine the hardness.’’ Adhesion was tested with reference to GB/T 9286-1998 ‘‘paint and varnish film crossgrid test.’’ Dried film (approximately $10\\ \\mathrm{cm}\\times5\\ \\mathrm{cm}$ ) was fixed on millimeter grid paper (grid: $1\\ \\mathrm{mm}\\ \\times\\ 1$ mm), and Scotch tape (3M, width $1.5\\ \\mathrm{cm}$ ) was pasted tightly onto the glass substrate. The number of grids covered by tape was recorded as $A_{0}$ . The tape was then pulled off quickly at angle of $180^{\\circ}$ , and the number of grids covered by the remaining film was recorded as $A$ . The adhesion22 of the film was then calculated as \n\n$$\n{\\mathrm{Adhesion~}}(\\%)={\\frac{\\mathrm{A}}{\\mathrm{A}_{0}}}\\times100\n$$ \n\nThe test results were categorized into six grades, from 0 as the best to 6 as the worst. Impact strength was tested with reference to GB/T 1732-1993 ‘‘film impact resistance test.’’ Water absorption was investigated by immersing dried resin film (approximately $\\mathrm{{\\bar{1}}c m}\\times\\mathrm{{\\bar{1}}c m}$ , weight $M_{0.}$ ) into water for $\\bar{24}\\mathrm{{h}}$ . The film was then taken out of the water, and after the water on the surface had been removed using filter papers, the film was weighed immediately $(M_{1})$ . The water absorption22 of the film was then calculated as \n\n \nFig. 2: FTIR spectra of (a) PAAMH-IH, (b) PAAMH, and (c) IPHE \n\nWater absorption $(\\%)=\\frac{M_{\\mathrm{1}}-M_{\\mathrm{0}}}{M_{\\mathrm{0}}}\\times100.$ \n\nContact angles were tested using a DataPhysics OCA40 equipped with environmental chamber. Three drops of water were used for each measurement, and average contact angle values were recorded. Samples were prepared on transparent glass, with another, analogous glass used as background, and a doublebeam UV–Vis spectrophotometer (Beijing, TU-1901) was used to measure the transparency of the coating. Differential scanning calorimetry (DSC, Netzsch 204F1, Germany) measurements were carried out in the temperature range from $-20$ to $150^{\\circ}\\mathrm{C}$ under ${\\bf N}_{2}$ atmosphere at heating rate of $30^{\\circ}\\mathrm{C/min}$ . To test their antifog properties, different samples were held above hot water $({\\bar{8}}0^{\\circ}\\mathrm{C})$ for $15\\mathrm{~s~}$ .",
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"category": " Materials and methods"
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},
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"id": 8,
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"chunk": "# Results and discussion",
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"category": " Results and discussion"
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},
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"id": 9,
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"chunk": "# FTIR spectroscopy \n\nThe FTIR spectra of IPHE, PAAMH, and PAAMHIH are shown in Fig. 2. Comparing spectra (a) and (c), the peaks at 1527 and $3360~\\mathrm{cm}^{-1}$ correspond to $-\\mathrm{\\mathbf{N}\\mathrm{\\mathbf{H}}}$ bending vibration and stretching vibration. The peak at $3300~\\mathrm{cm}^{-1}$ in spectrum (b) corresponds to hydroxyl absorption. As shown in Fig. 2, the absorption peak of $\\scriptstyle{\\mathrm{C=C}}$ stretching vibration at about $1640^{\\cdot}\\mathrm{cm}^{-1^{\\cdot}}$ disappeared from curve (b), indicating completion of the free-radical polymerization process. The reappearance of the $C{=}C$ absorption peak in curve (a) indicates successful introduction of IPHE. Comparing curves (c) and (a), the absorption peak of –NCO for IPHE at $2270~\\mathrm{{cm}^{-1}}$ disappeared from curve (a), indicating successful reaction of IPHE with PAAMH. Additionally, a strong absorption peak due to a sulfonic group was observed at about $11\\dot{7}0~\\mathrm{cm}^{-1}$ , suggesting successful introduction of AMPS. A weak absorption peak at $1020~\\mathrm{cm}^{-1}$ is attributed to $_{\\mathrm{Si-O-Si}}$ stretching, indicating successful introduction of MPS.",
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"category": " Results and discussion"
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},
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"id": 10,
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"chunk": "# $\\mathbf{\\nabla}^{I}H$ and $^{I3}C$ NMR analysis \n\n$^1\\mathrm{H}$ and $^{13}\\mathrm{C}$ NMR techniques were employed to further confirm the structure of the prepolymer. The spectra for PAAMH are shown in Fig. 3, showing peaks for two methylene protons from the main chain $\\left(\\mathrm{-CH}_{2}\\mathrm{-}\\right)$ at $1.20~\\mathrm{ppm}$ and from two methyl protons $\\left(\\mathrm{CH}_{3^{-}}\\right)$ linking with acrylamide at 1.31 ppm. The signal for methylene $(-\\mathrm{CH}_{2}\\mathrm{-}\\mathrm{SO}_{3}\\mathrm{H})$ protons directly attached to sulfonic acid group appeared at $3.45~\\mathrm{ppm}$ . In combination with the FTIR spectra, the $^1\\mathrm{H}$ NMR spectrum further indicates introduction of AMPS. The signals at 4.08 and $1.44~\\mathrm{ppm}$ are due to two methylene protons directly connected with ester bond from both MPS and HEA. The signal for a methylene group (OH– $\\mathrm{CH}_{2^{-}}\\mathrm{\\rangle}$ ) proton directly connected to hydroxyl groups appears at $2.23~\\mathrm{ppm}$ , proving successful introduction of MPS and HEA. \n\nThe $^{13}\\mathrm{C}$ NMR spectrum showed no peaks at $\\delta$ of $100{-}165~\\mathrm{ppm}$ , indicating no olefin. The saturated carbon $\\left(-\\mathrm{CH}_{2}\\mathrm{-CH}_{2}-\\right)$ absorption peak at $-2.1$ to $43\\ \\mathrm{ppm}$ further demonstrates that the AA, AMPS, MPS, and HEA double bonds were fully open. Both the $^1\\mathrm{H}$ and $^{13}\\mathrm{C}$ NMR spectra confirm synthesis of PAAMH.",
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"category": " Results and discussion"
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"id": 11,
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"chunk": "# Water contact angle and water absorption of antifog coatings \n\nFigure 4 shows the water contact angle (CA) and water absorption of the different PAAMH-IH prepolymers. Note that the CA decreased while the water absorption rose with increasing AMPS content. For AMPS content of $10\\%$ , the water absorption by the film reached $18.2\\%$ and the surface was swelled and tacky, thus being unusable. This result can mainly be attributed to the increasing sulfonic acid group content.19 Considering the balance between CA and water resistance, the optimum content of AMPS in the prepolymer was $^{6-}$ $8\\%$ . Regarding the dosage of curing agent (TEOS), all used prepolymer PAAMH-IH- $6\\%$ .",
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"category": " Results and discussion"
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"id": 12,
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"chunk": "# Transparency of antifog coatings \n\nThe transparency of antifog coatings is crucial for their applications, as poor transparency limits their application in optical instruments.23 Figure 5 shows UV–Vis spectra of cured films with different TEOS contents (Table 2). With increasing TEOS content, the light transmission (at $700~\\mathrm{nm},$ ) reduced from above 95 to $85\\%$ , and the transparency was greatly affected. This is probably because, although most silanol (Si–OH) in the main chain reacted with MPS to form $_{\\mathrm{Si-O-Si}}$ bonds, a small amount of TEOS remained, forming $\\mathrm{SiO}_{2}$ nanoparticles, as shown in Figs. 6a–6c; all images show $\\mathrm{SiO}_{2}$ microspheres unevenly distributed on the coating surface, which reduced the transparency. \n\n \nFig. 3: (a) $\\mathsf{\\Omega}^{1}\\mathsf{H}$ and (b) $\\boldsymbol{^{13}0}$ NMR spectra of PAAMH",
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"category": " Results and discussion"
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},
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{
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"id": 13,
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"chunk": "# Spreading time and contact angle \n\nThe spreading time and CA of the PAAMH-IH films with different TEOS contents are shown in Fig. 7. As the TEOS content was increased from 1.83 to $9.17\\%$ , the CA decreased from $25.7^{\\circ}$ to $9.8^{\\circ}$ . This is mainly because TEOS formed hydroxyl groups on the coating surface, enhancing its hydrophilicity. During the crosslinking process, although some of the hydroxyl groups dehydrated and formed Si–O–Si bonds, there were still a large number of hydroxyl groups that failed to form $_{\\mathrm{Si-O-Si}}$ bonds. The formed Si–O–Si with low surface energy and poor compatibility easily migrates to the film surface during the curing process, taking hydroxyl groups to the film surface for microphase separation. According to curve (e) in Fig. 7, the TEOS content was higher than the other four groups, but the CA still showed an upward trend instead. Maybe more TEOS formed $\\mathrm{SiO}_{2}$ nanoparticles that were embedded into the film during curing, and the amount of hydroxyl groups that migrated to the surface decreased. Figure 7 shows that the spreading times on the coating (droplet volume $2~\\upmu\\mathrm{L}$ ) were very short, all being below $1500~\\mathrm{{\\bar{ms}}}$ . \n\n \nFig. 4: Water contact angle and water absorption of PAAMH-IH \n\n \nFig. 5: Transparency of antifog coatings",
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"category": " Results and discussion"
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"id": 14,
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"chunk": "# AFM analysis of antifog coatings \n\nFigure 8 shows AFM two-dimensional (2D) height maps and phase patterns for the PAAMH-IH films. The 2D height maps show that all the surfaces were smooth within a small range, all having average roughness $\\left(R_{\\mathrm{a}}\\right)$ close to 1.025. The coating flatness in regions without microspheres was still good. In general, lighter areas of AFM phase images correspond to hard segments while darker areas correspond to soft segments. The phase maps of the surfaces of the coatings in Fig. 8 show significant differences between light and dark, indicating distinct microphase separation. The gradual expansion of discontinuous dark areas from PAAMH-IH-a to PAAMH-IH-e indicates more obvious microphase separation with increasing TEOS dosage. \n\n \nFig. 7: Water contact angle and spreading time for (a) PAAMH-IH-a, (b) PAAMH-IH-b, (c) PAAMH-IH-c, (d) PAAMHIH-d, and (e) PAAMH-IH-e \n\n \nFig. 6: SEM images of PAAMH-IH coatings: (a) PAAMH-IH-a, (b) PAAMH-IH-c, and (c) PAAMH-IH-e \n\n \nFig. 8: AFM images of PAAMH-IH, (a) PAAMH-IH-a, (b) PAAMH-IH-c, and (c) PAAMH-IH-e \n\n \nFig. 9: DSC curves of PAAMH-IH: (a) uncured, (b) thermally cured with TEOS, (c) UV cured, and (d) dual cured",
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"category": " Results and discussion"
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"id": 15,
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"chunk": "# DSC analysis \n\nFigure 9 shows the DSC curves for PAAMH-IH. The curve for pure resin without curing is (a). Curve (b) is for the crosslinked film with just thermal curing with TEOS. Curve (c) is for the crosslinked film with just UV curing. Curve (d) is for the film with dual curing. Comparing (a) and (b), one finds that the glass transition temperature $(T_{\\mathrm{g}})$ of the film increased from 0.45 to $20.12^{\\circ}\\mathrm{C}$ , indicating the occurrence of the crosslinking reaction during film curing with formation of a crosslinked network structure. Comparing (a) and (c), the $T_{\\mathrm{g}}$ of the film rose from 0.45 to $73.62^{\\circ}\\mathrm{C}$ ， indicating that UV curing also occurred. Comparing (a), (b), (c), and (d), the gradually increasing $T_{\\mathrm{g}}$ confirms that a dual-curing reaction occurred.",
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"category": " Results and discussion"
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"id": 16,
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"chunk": "# Mechanical performance and water resistance of coatings \n\nTable 3 presents the film properties of the coatings with different TEOS content. The results in Table 3 show that all samples exhibited high pencil hardness, with the highest reaching 3H. This can be attributed to high crosslink density of the polymer and large cohesive energy of crosslinked molecules. According to the impact resistance results, with increasing TEOS content, the impact strength also increased. No cracking or peeling phenomena were observed on the surfaces after impact. The maximum impact strength reached $70\\ \\mathrm{cm}$ . The maximum adhesion grade of the film reached 0. This is because the silane coupling agent (MPS) in the main chain of PAAMH-IH reacted with hydroxyl groups on the glass substrate surface to form $\\dot{\\mathrm{Si-O-}}\\dot{\\mathrm{Si}}$ bonds. After soaking for $24\\mathrm{~h~}$ , none of the coatings showed whitening phenomenon, indicating excellent water resistance. These results demon \n\nTable 3: Effects of amount of TEOS on film properties \n\n\n<html><body><table><tr><td>Test item</td><td colspan=\"5\">TEOS (wt%)</td></tr><tr><td></td><td>PAAMH-IH-a</td><td>PAAMH-IH-b</td><td>PAAMH-IH-C</td><td>PAAMH-IH-d</td><td>PAAMH-IH-e</td></tr><tr><td>Pencil hardness</td><td>2H</td><td>3H</td><td>3H</td><td>3H</td><td>3H</td></tr><tr><td>Adhesion grade</td><td>1</td><td>1</td><td>0</td><td>0</td><td>0</td></tr><tr><td>Water resistance</td><td>No whitening</td><td>No whitening</td><td>No whitening</td><td>No whitening</td><td>No whitening</td></tr><tr><td>Impact resistance (mm)</td><td>60</td><td>65</td><td>70</td><td>70</td><td>70</td></tr></table></body></html> \n\n \n\n \nFig. 10: 1 Antifog property of coatings: (a) PAAMH-IH-a, (b) PAAMH-IH-b, (c) PAAMH-IH-c, (d) PAAMH-IH-d, (e) PAAMH-IH-e. 2 Comparison of transparency of films \n\nstrate that the UV-cured coating with proper formula exhibited excellent coating performance.",
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"category": " Results and discussion"
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},
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{
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"id": 17,
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"chunk": "# Antifog property of coatings \n\nThe antifog property of the coatings was tested, and the results are shown in Fig. 10-1. The transparency of the films is compared in Fig. 10-2. In each graph, the glass on the right is coated with PAAMH-IH antifog coating while the left side is left uncoated for reference. As shown by these pictures, the glass with antifog coating remained transparent while the uncoated glass became hazy due to water condensation. With increasing TEOS content, the transparency decreased, as shown in Fig. 10-2.",
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"category": " Results and discussion"
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},
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{
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"id": 18,
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"chunk": "# Conclusions \n\nA functional resin was successfully synthesized using IPDI, AMPS, HEA, MPS, and AA as raw materials. Mixing with TEOS as novel crosslinking agent enabled preparation of antifog coatings. DSC curves confirmed the crosslinking reaction between MPS and TEOS during film formation, resulting in a crosslinked network structure. AFM images revealed microphase separation on the coating surface with migration of Si– O–Si bonds to the surface of the coating, leading to good adhesion, hardness, and water resistance, compared with traditional antifog coatings. \n\nVarious characterization techniques were applied to determine the optimum amounts of AMPS and TEOS. When the amount of AMPS was increased from 2 to $10\\%$ , the hydrophilicity of the coating increased, but the water absorption also increased, reaching a value of $18.2\\%$ , indicating poor water resistance. When the amount of TEOS was increased from 1.83 to $9.17\\%$ , the hardness, hydrophilicity, and water resistance increased, but the transparency decreased. Overall, the coating produced using $6{-}8\\%$ AMPS and $5.5\\%$ TEOS showed excellent antifog performance and mechanical properties. \n\nAcknowledgments This work was financially supported by the Natural Science Foundation of China (No. 51302109) and Natural Science Foundation of Jiangsu Province (BK20130144).",
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"category": " Conclusions"
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},
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{
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"id": 19,
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"category": " References"
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}
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