• Elastomers and Composites
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• v.52 no.3
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• pp.194-200
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• 2017

After the grafting of methacrylic acid (MA) to ethylene propylene diene monomer (EPDM), a new peak at $1704cm^{-1}$ corresponding to the carboxylic acid group was observed in the infrared (IR) spectrum. This characteristic MA molecule peak grew larger as the MA contents were increased. After casting films were prepared from pure EPDM and MA-grafted EPDM, differential scanning calorimeter (DSC) measurements were made the pure EPDM exhibited a melting point of approximately $45^{\circ}C$ while that of the MA-grafted EPDM was $135{\sim}140^{\circ}C$. As the graft ratio of MA increased, the absorbed heat capacity increased at temperatures near $135{\sim}140^{\circ}C$, indicating that an increased amount of MA reacted. Furthermore, owing to the addition of crystalline MA, it is expected that strength of the elastomer will improve as the graft ratio increases, as a result of the increased number of hard segments.

• Archives of Pharmacal Research
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• v.20 no.4
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• pp.324-329
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• 1997

AB-type amphiphilic copolymers (abbreviated as LE) composed of poly (L-leucine) (PLL) as the A component and poly (ethylene oxide) (PEO) as the B component were synthesized by the ring-opening polymerization of L-leucine N-carboxy-anhydride initiated by methoxy polyoxyethylene amine $(Me-PEO-NH_2)$ and characterized. Core-shell type nanoparticles were prepared by the diafiltration method. Particle size distribution obtained by dynamic light scattering was dependent on PLL composition and the size for LE-1, LE-2 and LE-3 was $369.6{\pm}267$, $523.4{\pm}410$ and $561.2{\pm}364 nm$, respectively. Shapes of the nanoparticies observed by transmission electron microscope (TEM) were almostly spherical. The critical micelle concentration (CMC) of the nanoparticles determined by a fluorescence probe technique was dependent on the composition of hydrophobic PLL, and the CMC for LE-1, LE-2 and LE-3 was $2.0{\times}10^{-6},1.7{\times}10^{-6}$ and $1.5{\times}10^{-6}(mol/l) $, respectively. Clonazepam release from core-shell type nanoparticles in vitro was dependent on PLL composition and drug loading content.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.735-740
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• 2019

The purpose of this study is to fabricate an ophthalmic lens by copolymerizing two types of carbon nanotubes and hydrophilic hydrogel lens materials, and to investigate its application as an ophthalmic lens material by analyzing its physical properties and antimicrobial effect. For polymerization, HEMA (2-hydroxyethyl methacrylate), EGDMA (ethylene glycol dimethacrylate), a crosslinking agent, and AIBN (azobisisobutyronitrile), an initiator, are used as a basic combination, and a single-walled carbon nanotube and a single-walled, carboxylic-acid-functionalized carbon nanotube are used as additives. To analyze the physical properties, the water content, refractive index, breaking strength, and antimicrobial effect of the fabricated lenses are measured. The fabricated lenses satisfies all the basic properties of the basic hydrogel ophthalmic lens. The water content increases with increasing amount of additive and decreases with addition of 0.2 % ratio of nanoparticles. The refractive index is inversely proportional to the water content result. As a result of the antimicrobial test of the fabricated lens, the addition of carbon nanotubes shows an excellent antimicrobial effect. Therefore, it is considered that the fabricated lens can be applied as a functional material for basic ophthalmic hydrogel lenses.

• Fibers and Polymers
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• v.1 no.1
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• pp.6-11
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• 2000

In the polycondensation reaction of polyethyleneterephthalate(PET), $Sb_2$$O_3$, can react effectively as a catalyst, if physically transformed. $Sb_2$$O_3$ powder is transformed into liquid solution by dissolving in ethylene glycol(EG). Homogeneous catalyst is made by mixing this liquid solution with glycols having different solubility. The efficient reaction of PET polymerization is expected by using homogeneous catalyst. PET was synthesized using homogeneous catalysts of 4 wt.% $Sb_2$$O_3$ solution dissolved in glycol[EG, 2,2-bis(4-(2-hydroxyethoxy)phenol)propane(BHPP), neopentyl glycol(NPO), and 1,3-propandiol(PD)]. PET using EG-BHPP($Sb_2$$O_3$) catalysts shows the highest I.V. within a reaction time of 120 min. In the p-d analysis, PET using EG-BHPP($Sb_2$$O_3$) catalysts has the fastest propagation rate and slowest degradation rate. EG-BHPP($Sb_2$$O_3$) catalysts are more efficient than EG($Sb_2$$O_3$) catalysts and $Sb_2$$O_3$ powder catalysts.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.288-296
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• 2009

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/$SiO_2$ hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/$SiO_2$ hybrid material with an improved optical transparency and homogeneous phase morphology.

• Textile Coloration and Finishing
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• v.27 no.3
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• pp.184-193
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• 2015

In this study, dye encapsulated microcapsules were produced by polyurethane prepolymer synthesis method using hexamethylene diisocyanate, ethylene glycol and methyl ethyl ketone. The study showed that the average size of microcapsules were $4.697{\mu}m$ in normal distribution. These microcapsules were induced red color by thermochromic fluoran red dye with showing color change as temperature. After the textile finishing of microcapsules, durability of microcapsules were checked as crocking times and lightfastness. The microcapsules were pressed at protrusion of textile weave in 10 crocking times which meant that the microcapsules not fallen off. Lightfastness was acceptable giving rating 4. It means that the polyurethane microcapsules not affect to light durability.

• Macromolecular Research
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• v.13 no.6
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• pp.467-476
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• 2005

The main objective of this study was to develop and characterize pH-sensitive biodegradable polymeric materials. For pH-sensitivity, we employed three kinds of moieties: 2-amino-3-(lH-imidazol-4-yl)-propionic acid (H), N-[4-( 4,6-dimethyl-pyrimidin-2ylsulfamoyl)-phenyl]succinamic acid (SM), and 2- {3-[ 4-( 4,6-dimethyl-pyrim­idin- 2-ylsulfamoyl)-phenylcarbamoyl]-propionylamino} -3-(3 H - imidazol-4-yl)-propionic acid (SH). The pH -sensitive diblock copolymers were synthesized by ring opening polymerization and coupling reaction from poly(ethylene glycol) (MPEG), $\varepsilon$-caprolactone (CL), D,L-lactide (LA) and pH-sensitive moieties. The pH-sensitive SH molecule was synthesized in a two-step reaction. The first step involved the synthesis of SHM, a methyl ester derivative of SH, by coupling reaction of SM and L-histidine methyl ester dihydrochloride, whereas the second step involved the hydrolysis of the same. The synthesized SM, SHM and SH molecules were characterized by FTIR, $^{1}H$-NMR and $^{13}C$-NMR spectroscopy, whereas diblock copolymers and pH-sensitive diblock copolymer were characterized by $^{1}H$-NMR and GPC analysis. The critical micelle concentrations were determined at various pH conditions by fluorescence technique using pyrene as a probe. The micellization and demicellization studies of pH-sensitive diblock copolymers were also done at different pH conditions. The pH-sensitivity was further established by acid-based titration and DLS analysis.

• Macromolecular Research
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• v.14 no.3
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• pp.359-364
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• 2006

Di-block copolymers composed of two biocompatible polymers, poly(ethylene glycol) and poly(D,L-lactide), were synthesized by ring-opening polymerization for preparing polymer vesicles (polymersomes). Emulsion solvent evaporation method was used to fabricate the polymersomes. Scanning electron microscope (SEM) images confirmed that polymersomes have a hollow structure inside. Confocal laser microscope and optical microscope were also used to verify the hollow structure of polymersomes. Polymersomes having various sizes from several hundred nanometers to a few micrometers were fabricated. The size of the polymersomes could be readily controlled by altering the relative hydrodynamic volume fraction ratio between hydrophilic and hydrophobic blocks in the copolymer structure, and by varying the fabrication methods. They showed greatly enhanced stability with increased molecular weight of PEG. They maintained their physical and chemical structural integrities after repeated cycles of centrifugation/re-dispersion, and even after treatment with surfactants.

• Polymer(Korea)
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• v.32 no.3
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• pp.219-229
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• 2008

A pH sensitive ternary copolymer gel was synthesized in the presence of ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent through radical polymerization of vinyl acetate (VA), acrylic acid (AA) and methyl acrylate(MA) with a weight ratio of 1 : 1.3 : 1. A number of experiments were carried out to determine the swelling behavior of the gel under a variety of pH conditions of the swelling medium. As the pH of the swelling medium was changed from 1.0 to 8.0 at $37^{\circ}C$, the gel showed a shift in the pH-dependent swelling behavior from Fickian (n=0.3447) to non-Fickian (n=0.9125). The resulting swelling parameters were analyzed using graphical and statistical methods. The results showed that the swelling of the gel was controlled by the pH of the medium, i.e. $n=n_o{\exp}(S_{C}pH)$, where n is the diffusion exponent, $n_o(=28.9645{\times}10^{-2})$ is the pre-exponential factor and $S_C$(=0.1417) is pH sensitivity coefficient. The swelling behavior of the gel was also examined in aliphatic alcohols. The results showed that the rate of swelling increased with increasing number of carbon atoms in the alcoholic molecular chain.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.223-225
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• 1996

Poly (ethylene glycol) (PEG)macromers terminated with acrylate groups and interpenetrating polymer networks(IPN) composed of poly(hydroxyethyl methacrylate)(PHEMA) or poly(hydroxyethyl methacrylate-co-hydropropyl methacrylate-co-N-vinyl pyrrolidone) [P(HEMA-co-HPMA-co-NVP)] and PEG macromer were synthesized with the aim of obtaining protein adsorption resisatnt soft contact lens. Polymerization of PEG macromer resulted in the formation of cross-linked gels due to the multifunctionality of macromer. Crosslinked P(HEMA) or P(HEMA-co-HPMA-co-NVP) chains were interpenetrated into the cross-linked three-dimensional networks of PEG. It was found that albumin adsorption onto the contact lens prepared by P(HWMA)/PEG IPN decreases with a decrease of molecular weight of PEG whereas its adsorption onto the contact lens prepared by P(HEMA-co-HPMA-co-NVP)/PEG IPN decreases with an increase of molecular weight of PEG. Also, it was found that albumin adsorption onto the both contact lens decreases with an increase of concentration of PEG macromer in the IPN preparation. There are also more adequate in the bioinertness and bioadhesion for the contact lens by P(HEMA)/PEG IPN or P(HEMA-co-HPMA-co-NVP)/PEG IPN than that by P(HEMA) or P(HEMA-co-HPMA-co-NVP).