• Journal of Pharmaceutical Investigation
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• v.24 no.4
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• pp.251-256
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• 1994

Polypropylene glycol (M.W. 4000) was crosslinked and chain-extended by using triisocyanate and diisocyanate to synthesize rubbery and water swellable hydrogels. Model drugs, i.e., sodium salicylate and indomethacin were incorporated in the polymer matrices by swelling loading. The drug release rates of drugs could be regulated by varying the degrees of crosslinking and chain-extension. Whereas, no correlation was observed between the drug release profiles and the swelling behaviours of the matrices. The release of drugs from the matrices was considered to be governed by the mobility and mesh size of the polymer chains in the matrices.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.356-356
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• 2006

The use of renewable feedstock is an important issue to reduce the fossil fuel consumption. In this contribution, we report the cationic ring-opening polymerization of a 2-oxazoline monomer with soybean fatty acid side chains (SoyOx) under microwave irradiation. Kinetic experiments were performed to investigate the livingness of the polymerization in both acetonitrile and in the absence of solvent. In addition, both block and statistical copolymers were prepared using the SoyOx monomer. The synthesized (co)polymers were crosslinked under UV-irradiation resulting in insoluble polymeric materials and core-crosslinked micelles.

• Journal of Radiation Industry
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• v.2 no.3
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• pp.105-110
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• 2008

Poly (VDF-co-HFP)/PEGDMA nanofibrous membranes (NFMs) have been prepared by an electrospinning process. Since electrospun NFMs have a nanoporous structure, they have a potential application for a polymer electrolyte or a separator. Poly (VDF-co-HFP) is a polymer electrolyte binder. In order to improve their mechanical properties, poly (VDF-co-HFP)/PEGDMA NFMs were crosslinked by a gamma-ray irradiation. Then the crosslinked NFMs were characterized through an electrolyte uptake, IR structural analysis, and SEM morphological investigation.

• Bulletin of the Korean Chemical Society
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• v.17 no.5
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• pp.443-447
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• 1996

Several polysilanes with sterically bulky substituents such as poly(2-phenylpropyl)(n-hexyl)silane were prepared by Wurtz-type coupling. The polysilane products were mixtures of low-molecular-weight polymers (&bar{M};w~103) as major and high-molecular-weight polymers (&bar{M};w~106) as minor. Overall yields for polysilanes were in the range of 81-99%. λmax of liquid low MW polymers appeared at around 280 nm. Formations of solid high MW polymers were decreased by a longer reaction time and increased steric bulkiness of substituents. High MW polymers with λmax at 327 nm except crosslinked polymers were soluble in common organic solvents and found to be light sensitive. Crosslinked high MW polymer gave 21% TGA ceramic yield, compared with linear high polymer giving zero ceramic yield.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1168-1171
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• 1998

Two kinds of second-order nonlinear optical copolymers were prepared by the copolymerization of the vinyl monomers containing NLO chromophore, methacrylic acid, and methyl methacrylate or butyl methacrylate. Glass transition temperatures (Tg of copolymers were around 130 ℃. The copolymers were soluble in common organic solvents such as tetrahydrofuran (THF), cyclohexanone, and N,N-dimethylformamide (DMF). The crosslinked copolymer was obtained by thermal treatment using pentaerythritol tetrakis(2-mercaptoacetate) as a crosslinker and became insoluble in tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). Poling was carried out at 120 ℃ for 20 min and identified with UV-Vis spectroscopy. Electro-optic coefficient (r33) measurement showed a value of 35 pm/V for polymer 2 at 633 nm. Temporal stability of copolymers was improved owing to the crosslinked network, which was successfully obtained at 170 ℃ for 30 min after poling.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.274-279
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• 1992

Immobilization method of lariat azacrown ethers, containing hydroxyl group in the side arm of crown ring, on the polymer matrix and the phase-transfer catalytic activity of thus obtained immobilized lariat azacrown ethers were studied. Polystyrene resins with crown ether structures and hydroxyl groups adjacent to the macrorings were prepared by the reaction of crosslinked polystyrene resins containing epoxy groups with monoaza-15-crown-5 or monoaza-18-crown-6. Microporous crosslinked polystyrene resins containing epoxy group for the syntheses of these immobilized lariat crown catalysts were prepared by suspension polymerization of styrene, divinylbenzene (DVB 2%) and vinylbenzylglycidyl ether. The immobilized lariat catalysts with 10-20% ring substitution exhibited maximal activity for the halogen exchange reactions of 1-bromooctane with aqueous KI or NaI under triphase heterogeneous conditions. Immobilized catalyst exhibited higher activity than corresponding catalyst without the hydroxyl group and this result was suggested that the active site have a structure in which the $K^+$ ion was bound by the cooperative coordination of the crown ring donors and the hydroxyl group in the side arm.

• Macromolecular Research
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• v.17 no.5
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• pp.325-331
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• 2009

The synthesis and the characterization of crosslinked ABC triblock copolymer, i.e. polystyrene-b-poly (hydroxyethyl methacrylate)-b-poly(styrene sulfonic acid), (PS-b-PHEMA-b-PSSA) is reported. PS-b-PHEMA-b-PSSA triblock copolymer at 20:10:70 wt% was sequentially synthesized via atom transfer radical polymerization (ATRP). The middle block was crosslinked by sulfosuccinic acid (SA) via the esterification reaction between -OH of PHEMA and -COOH of SA, as demonstrated by FTIR spectroscopy. As increasing amounts of SA, ion exchange capacity (IEC) continuously increased from 2.13 to 2.82 meq/g but water uptake decreased from 181.8 to 82.7%, resulting from the competitive effect between crosslinked structure and the increasing concentration of sulfonic acid group. A maximum proton conductivity of crosslinked triblock copolymer membrane at room temperature reached up to 0.198 S/cm at 3.8 w% of SA, which was more than two-fold higher than that of Nafion 117(0.08 S/cm). Transmission electron microscopy (TEM) analysis clearly showed that the PS-b-PHEMA-b-PSSA triblock copolymer is microphase-separated with a nanometer range and well developed to provide the connectivity of ionic PSSA domains. The membranes exhibited the good thermal properties up to $250^{\circ}C$ presumably resulting from the microphase-separated and crosslinked structure of the membranes, as revealed by thermal gravimetric analysis (TGA).

• Polymer(Korea)
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• v.28 no.1
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• pp.92-102
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• 2004

(6-Cholesteryloxycarbonylpentoxypropyl)celluloses (CHPCs) with degree of esterification (DE) ranging from 2.25 to 2.91 were synthesized by reacting hydroxypropyl cellulose with 6-cholesteryloxycarbonylpentanoyl chloride. The acrylic esters of CHPCs (CHPCEs) and their photocrosslinked films with liquidcrystalline order were also synthesized. The thermotropic properties of mesophase for both uncrosslinked and crosslinked samples and the swelling behavior of the crosslinked samples in acetone were investigated. The hydroxypropyl cellulose exhibited an enantiotropic cholesteric phas, while all the uncrosslinked cholesterylbearing samples exhibited a monotropic cholesteric phases; the 6-cholesteryloxycarbonylpentanoyl chloride also showed a monotropic smectic phase. The hydroxypropyl cellulose formed a right-handed helix whose optical pitch (λ$\sub$m/) increases with temperature, whereas all the uncrosslinked derivatives farmed left-handed helices whose λ$\sub$m/'s decreased with temperature. The thermal stability of the mesophase and the magnitude of λ$\sub$m/ at the same temperature for both CHPCs and CHPCEs decreased with increasing DE. All the crosslinked samples, in constrast with CHPCEs, did not display reflection colors but exhibited an anisotropic swelling characteristic of crosslinked gel retaining liquid-crystalline order.

• Polymer(Korea)
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• v.24 no.2
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• pp.252-258
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• 2000

Various crosslinked poly(4-vinylpyridines) (CHP4VP) having different degrees of crosslinking were synthesized by radical copolymerization of 4-vinylpyridine with if N,N' -1, 6-hexamethylenebisacrylamide, and CHP4VP- Cu(II) complexes were prepared by the method of adsorption equilibrium. The catalytic activity of the complexes for the oxidation of ascorbic acid (AA) was investigated. The oxidation of AA by these complexes showed a kinetic behavior of the Michaelis-Menten type. The catalytic activity of CHP4VP-Cu(I ) catalytic system was increased with increasing the degree of crosslinking of CHP4VP, and its activity was scarcely decreased even after repeated use. However, the tendency of the catalytic activity of CHP4VP-Cu(II) complexes was decreased for the oxidation of AA when compared with that of the previously reported catalytic system containing crosslinked poly(4-vinylpyridine) prepared using N,N'-methylenebisacrylamide as a crosslinker. These results indicate that the degree of crosslinking of CHP4VP and the hydrophobicity of the crosslinker play an important role in the catalytic system of the oxidation of AA.

• Macromolecular Research
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• v.17 no.5
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• pp.339-345
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• 2009

The core/shell type structure of the highly crosslinked poly(glycidylmetharylate-co-divinylbenzene) microspheres prepared in the precipitation polymerization in acetonitrile was thoroughly verified by means of swelling, $^1H$ NMR, XPS, TEM and TGA measurements. In the XPS measurement, the higher the GMA content, the higher the oxygen content was observed, implying that the higher content of GMA is observed in the particle surface. The further verification of the core/shell structure of the poly(GMA-co-DVB) particles was carried out using $^1H$ NMR and TEM techniques, resulting in the poly(GMA-co-DVB) particles with the GMA rich-phase and DVB rich-phase. In overall, the poly(GMA-co-DVB) microspheres consist of a highly crosslinked DVB rich-phase in the core and slightly or non-crosslinked GMA rich-phase in the shell part due to the different reaction ratios between two monomers and self-crosslinking density of DVB.