• Journal of Pharmaceutical Investigation
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• v.32 no.4
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• pp.327-330
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• 2002

Alginate based polymeric matrices were designed for controlled release and stabilization of cefaclor in gastrointestinal fluid. Cefaclor is known to be acid stable and subjected to be degraded at neutral and alkaline pHs. In order to achieve an effective release profile of cefaclor in gastrointestinal tract, a particular strategy in dosage form design should be required from the view point of maintaining its activity. The amphiphilic nature of cefaclor allowed its controlled release using ionic polymers based on ionic interaction between the drug and polymers. The thrust of this study was to develop a technique that delivers cefaclor keeping effective release rate in the intestinal tract. Considering the fast degradation of cefaclor in the intestinal fluid, the matrices were designed to release surplus amount of cefaclor. The alginate based matrices demonstrated increase in release rate in the simulated intestinal fluid, which was favorable to compensate the degraded portion of cefaclor. In addition, stabilization of cefaclor in the intestinal fluid was obtained by employing citric acid that provides an local acidic environment. The matrices might be valuably used for the development of an oral cefaclor dosage form.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.2
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• pp.66-71
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• 2011

Biocomposites were fabricated with biodegradable polymers and natural fibers. Biocomposites have benefits of low cost, low density, and biodegradability over inorganic fiber composite, and give comparable strength properties. Hydrophobic polymer used for sizing in paper industry, AKD (Akenyl Keten Dimer), was applied to natural fibers, red algae fibers (RAF) in this study, to make fiber surfaces more compatible to hydrophobic nature of matrix polymers. Composites with RAF, kenaf, glass fibers, and carbon fibers have been fabricated by a compression molding method and their thermo-mechanical properties have been studied. Also, the thermal dimensional stability test was done from at 30 to $100^{\circ}C$. The storage moduli and the thermo-mechanical stabilities of polypropylene and poly lactic acid based biocomposites were improved by reinforcing with the RAF and much more with AKD treated fibers. Dimensional stability of biocomposite was also markedly improved by AKD pretrement on RAF.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1061-1068
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• 1996

The conducting polymer composites were prepared by imbibing the porous particle wish the $FeCl_3$ oxidant solution, drying the imbibed porous particle, and imbibing again with pyrrole solution for polymerization to take place in the pore of porous particles. The effect of synthesis conditions on the conductivity of composite polymers were investigated. It was found that the conductivity of composite polymers was dependant on the concentration of pyrrole monomer, nature of the oxidants and solvents used for the oxidant and pyrrole, which influence the degree of penetration/distribution of polyprrole in the composite and reaction of dopant with pyrrole.

• Clean Technology
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• v.17 no.1
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• pp.1-12
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• 2011

Scientists and engineers have altered the properties of materials such as metals, alloys, polymers, ceramics, and so on, to suit the ever changing needs of our society. Man-made engineering materials generally demonstrate excellent mechanical properties, which often tar exceed those of natural materials. However, all such engineering materials lack the ability of self-healing, i.e. the ability to remove or neutralize microcracks without intentional human interaction. The damage management paradigm observed in nature can be reproduced successfully in man-made engineering materials, provided the intrinsic character of the various types of engineering materials is taken into account. Various self-healing ptotocols that can be applied for the organic materials such as polymers, ionomers and composites can be developed by utilizing suitable chemical reactions and physical intermolecular interactions.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.176-180
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• 2005

The liquid crystalline properties of a series of main chain liquid crystalline polymers and four series compounds consisting of aromatic type Schiff base mesogenic units and polymethylene flexible spacers were studied. The thermal and liquid crystalline properties were investigated by differential scanning calorimetry and on the hot stage of a polarizing microscope. The nature of the liquid crystalline phase of the polymers and compounds depended greatly on the length of the central polymethylene spacer and on the terminal alkoxy groups. Polymers I and Series III exhibited an even-odd effect in melting and isotropization temperatures but Series II and Series IV exhibited an even-odd effect in isotropization temperatures. They formed nematic and smectic mesophases in melts as judged by their optical textures observed through a polarizing microscope.

• Fibers and Polymers
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• v.5 no.4
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• pp.253-258
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• 2004

Living nature of photoinduced cationic polymerization of isobutyl vinyl ether (IBVE) in the presence of various combinations of diphenyliodonium halide (DPIX), a photocationic initiator and zinc halide $(ZnX_2)$ in methylene chloride has been investigated. Attainment of $100\%$ conversion and a linear relationship between $\%$conversion and number average molar mass of the resulting polymer, strongly suggests the living nature of this system. Livingness of the polymerization system was observed irrespective to the type of halide anion of the initiator and zinc salts unless the reaction temperature is not higher than $-30^{\circ}C$. The rate of polymerization decreases in the order of iodide > bromide > chloride when halide salt of DPIX and $ZnX_2$ are used. It is postulated that the cationic initiation is started by the insertion of weakly basic monomer in to the activated C-X terminal of the monomer adduct which is a reaction product of monomer and HX, a photolytic product of DPIX, formed in situ during the photo-irradiation process. It was concluded that polymerization is initiated by the insertion of weakly basic monomer into activated C- X terminal of monomer adduct due to the pulling action of$ZnX_2$, which successively producing a new polarized C-X terminal for the propagation in cationic nature. This led us to a conclusion that the living nature of this cationic polymerization is ascribable to the polarized C-X growing terminal, which is stable enough to depress the processes of chain transfer or termination process.

• Fibers and Polymers
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• v.7 no.4
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• pp.432-435
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• 2006

High Modulus and high tenacity polypropylene fibers have been prepared by drawing on a gradient heater. Results show that fiber properties are significantly affected by temperature profiles of final stage drawing on a gradient heater. The gradient drawn filaments showed superior mechanical properties when compared to filaments drawn over a constant temperature heater. Fibers with initial modulus of 16.4 GPa and tenacity of 670 MPa have been manufactured in the process. The nature of the gradient drawing had a significant effect on end properties. The superior mechanical properties are attributed to the high crystal perfection and crystallinity and low void fractions obtained at high draw ratios when drawn over a gradient heater.

• Textile Coloration and Finishing
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• v.2 no.4
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• pp.237-244
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• 1990

Syntheses and liquid-Crystallinites of thermotropic copoly (ester amide)s were investigated. The three components melt polycondensation of 4,4'-dicarboxy-$\alpha$, $\omega$-diphenoxyalkane as an A component, 4-4'diacetoxybiphenyl as a B, and p-N-acetoxy-aminobenzoic acid as a C gave the thrmotropic copoly(ester amide)s containing a flexible splacer in the polymer backbone. Diacetylated hydroquinone, methyl hydroquinone, chlorohydroquinone, and phenyl hydroquinone were used as anther B components. A polymer(6BPAB) having 10 mol% of C component and hexamethylene space. showed a typical nematic texture between $245^{\circ}C(T_m)\; and\; more\; than\; 360^{\circ]C(T_i)$. The melting points of the members of this series of polymers increased with decreasing methylene spacer. The polymer structure and mesomorphic nature were examined by solid and solution ^{13}C-NMR4 spectroscopy, cross polarizing microscopy with a hot stage, and X-ray diffactometry.

• Textile Coloration and Finishing
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• v.4 no.3
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• pp.97-115
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• 1992

In order to improve the processability of rigid rod-like polyspiroacetals without significant loss of their good nature, in this work a few new ideas for molecular design were adopted: (1) Copolymerization for breaking the regularity of polymer repeating units. (2) Incorporation of flexible methylene linkages or spacers in rigid spiroacetal polymer main chain. (3) Derivatization of long flexible side chains onto rigid polymer backbone. On the basis of these ideas, a series of polyspiroacetals were prepared, using the phase transfer catalyst, BTMAC, by interfacial polymerization reactions of spiroacetal monomer (SAB) and disubstituted aromatic acid chlorides or aliphatic diacid chlorides. Physical properties of these polyspiroacetals are discussed in relation to their chemical structure and are compared with those of polyspiroacetals synthesized by several other researchers.

• Textile Coloration and Finishing
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• v.5 no.2
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• pp.109-116
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• 1993

Synthesis and liquid-crystallinites of thermotropic polyamides and copolyamides were investigated. Thermotropic polyamides and copolyamides containing a flexible spacer in the backbone were obtained by the two or three components melt polycondensations of 4,4'-dicarboxy-${\alpha}$${\omega}$-diphenoxy alkane as an A components, 4,4'-diacetoamido-3,3' dimethoxybiphenyl as a B, 1,4-diacetoamido-benzene (diacetylated p-phenylenediamine) was used as another amide-group-forming minomer. The content of the amide groups in the thermotropic polyamide and Copolyamide widely varied depending on the structure of the amide-group forming diacetoamido monomers. A polymer (9CLDI) showed a typical nematic texture between 218$^{circle}C$ ($T_m$) and 345$^{circle}C$($T_i$) The melting points of the members of this series of polymers increased with decreasing methylene spacer. The polymer structure and mesmorphic nature were examined by solid and solution ${^13}C$-NMR spectroscopy, cross polarizing microscopy with a hot stage.