• Polymer(Korea)
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• v.24 no.2
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• pp.168-173
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• 2000

Radical copolymerization of N-isopropylacrylamide (NIPAAM) with methyl methacrylate (MMA) was carried out in 1,4-dioxane using 2,2'-azobisisobutyronitrile (AIBN). To investigate the reactivity ratios of NIPAAM and MMA at different reaction temperatures, the copolymerization was allowed to proceed to low conversion (less than 10 wt%), and the reaction temperatures were 50, 60, and 7$0^{\circ}C$. The monomer reactivity ratios of NIPAAM and MMA were estimated by the graphical methods according to the Finemann-Ross equation. The ${\gamma}$$_1$ and ${\gamma}$$_2$ values for NIPAAM-MMA were 0.259 and 2.782 at 5$0^{\circ}C$, 0.271 and 2.819 at 6$0^{\circ}C$, and 0.286 and 2.915 at 7$0^{\circ}C$, respectively. As the reaction temperature increased, the ${\gamma}$$_1$ and ${\gamma}$$_2$ values increased. The activation energy difference was estimated by comparing the reactivity ratios at different reaction temperatures.

• Polymer(Korea)
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• v.33 no.5
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• pp.477-484
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• 2009

Suspension polymerization with hydrophobic silica as a stabilizer and AIBN as an initiator was conducted to synthesize PBMA particles and PBMA composite particles containing carbon black. Surface modification of silica particles by controlling pH revealed that 90% of them functioned as stabilizer and 10% were incorporated into PBMA particles. While stabilizer concentration had no impact on reaction kinetics and particle diameter, an increase in stabilizer concentration displayed an increase in molecular weights when it exceeded 1.67 wt%. An increase in initiator concentration and reaction temperature decreased molecular weights in close agreement with the theoretical equation. An increase in carbon black concentration from 1 to 7 wt%, relative to the monomer, showed a progressive decrease in reaction conversion. As carbon black was increased from 3 to 5 wt%, glass transition showed a $4^{\circ}C$ increase. The presence of carbon black was confirmed by TEM while its concentration was measured by TGA.

• Membrane Journal
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• v.23 no.3
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• pp.220-225
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• 2013

Hydrophilic monomers were polymerized for lamination on polyvinylidene fluoride (PVDF) membrane surface for hydrophilization of the membranes. Hydrophilization reduced the contact angle from $95^{\circ}$ to $55^{\circ}$ and enhanced the water flux by 10 times while it reduced the bovine serum albumin (BSA) adsorption amount to 1/4 level. Thermal polymerization process was optimized by examining several operation parameters. Dimethyl oxobuthyl acrylamide (DOAA) showed the best effect due to its better hydrophilicity than others. Increase of amount of monomer enhanced the performance until the optimum concentration of 30 wt%, beyond which excess amount of monomer resulted in homopolymerization to deteriorate the performance. Azobis (isobutyronitrile)(AIBN) initiator has greater activation temperature range than benzoyl peroxide (BPO) and it showed better hydrophilation performance. Two stage lamination process, application of initiator followed by monomer addition, was more effective than one stage process, addition of initiator and monomer at once, which still reduced the contact angle but also reduced the water flux by pore blocking phenomena.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.317-322
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• 2010

This study used 4-fluorostyrene with the cross-linker EGDMA (ethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate) and the initiator AIBN (azobisisobutyronitrile) for copolymerization. Measurement of the physical properties of the copolymerized polymer showed that the water content was 19.98 ~ 31.08%, refractive index 1.443 ~ 1.475, visible transmittance 87 ~ 93% and tensile strength 0.246 ~ 0.311 kgf while the contact angle showed a distribution between $54.14^{\circ}$ and $66.95^{\circ}$. Therefore, the ophthalmic material produced using 4-fluorostyrene satisfied the basic physical properties required for contact lenses and also showed an increase in wettability and refractive index while having no significant change in water content with relation to styrene. Based on the results of this study, the produced copolymer is suitable for use as a material to high refractive index and wettability contact lenses.

• Journal of the Korean Chemical Society
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• v.56 no.5
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• pp.597-602
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• 2012

The copolymerization of triacetoxyvinylsilane, EGDMA (ethylene glycol dimethacrylate as a cross-linker), HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), MA (methacrylic acid) was performed in the presence of AIBN (2,2'-azobisisobutyronitrile) as an initiator. Measurement of the physical properties of the resulting copolymers showed that water content, refractive index, visible ray transmittance, and tensile strength were in the range of 35.63~32.44%, 1.4382~1.4480, 89.0~92.5% and 0.346~0.674 kgf, respectively. The values of tensile strength of copolymers-containing hexamethylene diisocyanate were higher than those of the copolymers containing triacetoxyvinylsilane. From the results we came to the conclusion that the produced copolymers are suitable for the application of ophthalmic contact lens with high tensile strength, wettability and duraility.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.761-765
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• 2010

Poly (N,N-dimethylacrylamide) is very useful in various fields due to its remarkable properties, such as water solubility and biocompatibility. This study used N,N-dimethylacrylamide with the cross-linker EGDMA (ethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), NVP (N-vinyl-2-pyrrolidone) and the initiator AIBN (azobisisobutyronitrile) for copolymerization. Measurement of the physical properties of the copolymerized polymer showed that the water content was 36 - 42%, refractive index was 1.433 - 1.426 and visible ray transmittance 90 - 91% while the oxygen permeability showed a distribution between 13.1 and $21.29{\times}10^{-11}(cm^2/sec)$ ($mlO_2/mL{\times}mmHg$). The measurement showed that the increased amount of oxygen permeability of the copolymer measured using the polarographic method range between 11.0% and 80.5%. Based on the results of this study, the produced copolymer is suitable for use as a material to high oxygen permeability hydrogel lenses.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.755-760
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• 2010

This study used 3-vinylanisole and 4-vinylanisole with the cross-linker EGDMA (ethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), NVP (N-vinyl-2-pyrrolidone) and the initiator AIBN (azobisisobutyronitrile) for copolymerization. Measurement of the physical characteristics of the copolymerized material showed that the refractive index is 1.4496 - 1.4894, water content 22.93 - 35.50%, visible transmittance 88.8 - 90.8%. Also, measurements showed that the refractive index increased while the water content decreased as the ratio of 3-vinylanisole and 4-vinylanisole increased. And in cases of copolymer with 3-vinylanisole, 4-vinylanisole (added 15%) the results showed transmittance of 52.8 - 82.2%, 13.2 - 26.2% respectively for UV-A and UV-B showing that they have UV-blocking effects. Based on the results of this study, the produced copolymer can be estimated to be suitable for use as ophthalmic lens material for high refractive index and UV- blocking effects.

• Journal of the Korean Applied Science and Technology
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• v.22 no.4
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• pp.362-370
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• 2005

Copolymers (HSA-98-20, HSA-98-0, HSA-98+20) which are acrylic resin containing 80% solid content were synthesized by the reaction of monomers, including methyl methacrylate, n-butyl acrylate, and 2-hydroxyethyl acrylate with a functional monomer, such as acetoacetoxyethyl methacrylate (AAEM), which may improve in cross-linking density and physical properties of films. The physical properties of prepared acrylic resins, containing AAEM, are as follows : viscosity, $1420{\sim}5760cps$ ; number average molecular weight, $2080{\sim}2300$ ; polydispersity index, $2.07{\sim}2.19$ ; conversions, $88{\sim}93%$, respectively. To prepare acryl resins, four kinds of initiators including ${\alpha},{\alpha}'-azobisisobutyronitirile$ (AIBN), di-tert-butyl peroxide (DTBP), t-amylperoxy-2-ethyl hexanoate (APEH), benzoyl peroxide (BPO) were used. The viscosity of the acrylic resins prepared with these initiators was increased in the order of DTBP>APEH>AIBN>BPO. APEH was proved as a suitable initiator in this study. Shear rates of acrylic resins were constant in respect to viscosity. From these results, it would appear that the resins have Newtonian flow characteristics and good workability.

• Polymer(Korea)
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• v.26 no.1
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• pp.9-17
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• 2002

The free radical bulk copolymerizations of perfluoroalkylethyl acrylate(FA) containing perfluoro group ($CF_3(CF_2)_nCH_2CH_2$-; n=5, 7, 9, 11) with styrene were conducted at $60^{\circ}C$ using AIBN as an initiator. Reactivity ratios($r_1$, $r_2$) were determined from monomer feed compositions and the NMR spectroscopically measured copolymer compositions using Kelen-Tudos method. The structures of copolymers were characterized with FT-IR and $^1H-NMR$ analysis. Their thermal properties investigated with DSC and TGA were decreased with increasing the content of fluorinated acrylate in the copolymer. Their surface free energies were calculated with measuring contact angles of the copolymers and PMMA blends with a small amount of them.

• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.547-552
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• 2009

Chitosan, a natural polymer, has been importantly considered as biomedical materials due to its good biocompatibility and various bio-active characteristes. Water soluble chitosan was then copolymerized EGDMA(ethylene glycol dimethacrylate; used as a cross-linking agent for the free-radical copolymerization), MMA (methylmethacrylate), MA (methacrylic acid) in the presence of AIBN (azobisisobutyronitrile) as a radical initiator. The water content and visible transmissibility, ultimate strength of copolymerized ophthalmic polymer were measured to be 24$\sim$59%, 88$\sim$89% and 0.1$\sim$2.4 Kgf, respectively. And also, we tested for antimicrobial activities against staphylococcus aureus, Pseudomonas aeruginosa. They showed that in case of antimicrobial activities, the values including chitosan were much higher than that of the polymers of no including chitosan, suggesting that the copolymer can be used as a novel ophthalmic material of high performance.