• Polymer(Korea)
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• v.25 no.1
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• pp.108-114
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• 2001

Crosslinked poly(glycerol-co-malate)s were synthesized from L-malic acid in Krebs cycle and glycerol. The synthesized polymer was identified by FT-IR spectroscopy. Swelling degrees of the copolymer hydrogels were increased with an increase in pH of the aqueous solution. Hydrolytic behaviors of the crosslinked copolymers were investigated in various pH buffer solutions at 37${\circ}C$. The Hydrolysis of the copolymers proceeded faster with increasing pH of the aqueous solution. Releasing behaviors of the model drug such as diclofenac monosodium salt were also measured in various pH aqueous solutions at 37${\circ}C$. The release concentration of diclofenac monosodium salt from the hydrogel systems was increased with increasing pH. These facts indicate that the unreacted carboxyl and hydroxyl groups in the copolymers are greatly affected by pH in the conditions.

• Macromolecular Research
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• v.11 no.1
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• pp.25-35
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• 2003

A series of random poly(ethylene-co-1,4-butylene terephthalate)s (PEBTs), as well as poly(ethylene terephthalate) (PET) and poly(1,4-butylene terephthalate) (PBT), were synthesized by the bulk polycondensation. Their composition, molecular weight, and thermal properties were determined. All the copolymers are crystallizable, regardless of the compositions, which may originate from both even-atomic-numbered ethylene terephthalate and butylenes terephthalate units that undergo inherently crystallization. Non-isothermal crystallization exotherms were measured over the cooling rate of 2.5-20.0 K/min by calorimetry and then analyzed reasonably by the modified Avrami method rather than the Ozawa method. The results suggest that the primary crystallizations in the copolymers and the homopolymers follow a heterogeneous nucleation and spherulitic growth mechanism. However, when the cooling rate increases and the content of comonomer unit (ethylene glycol or 1,4-butylene glycol) increases, the crystallization behavior still becomes deviated slightly from the prediction of the modified Avrami analysis, which is due to the involvement of secondary crystallization and the formation of relatively low crystallinity. Overall, the crystallization rate is accelerated by increasing cooling rate but still depended on the composition. In addition, the activation energy in the non-isothermal crystallization was estimated.

• Korean Journal of Crystallography
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• v.2 no.2
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• pp.13-21
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• 1991

X-ray methods have been used to determine the chain conformation and packing of the thermotropic liquid crystalline copolyester prepared from 50% tarephthaloyl chloride(TPA) and 50% (1-phenylethyl) hydroquinone(PEHQ). The x-ray patterns of annealed melt-spun fibers contain a series of annealed melt-Pointing to a well ordered crystalline structure, despite the random sense(2 or 3-) of the 1-phenylethyl substiuttion on the TPA-hydroquinone backbone. The crystalline fiber is monoclinic with space group P2l and the unit cell has dimensions 11=12.77 A, b=10.17 A (upique axis), c=12.58 h (fiber axis). and β=90.1° and contains TPA-PEHO units of to or chains. The random substitution of 1-phenylethyl groups was modelled by placing these groups at both the 2and 3 positions and giving each a weight of one-hal(. T he structure has been refined by linked a rom least square methods(LALS) against 16 observed and 21 unobserved reflections. and had a final R value of 0.20. Packing of the side chains is effected by staggering adjacent chains along the b axis by approximately c/2, so that the side chains are interleaved. The phenyl-COO and COO-phenyl torsion angles are -6.1 and 65.6, respectively, such that the main chain phenyls are mutually inclined at 59.5 (the ester groups are assumed to be planar). These torsion angles compare very well with those for the model compounds, notably phenylbenzoate, and can be used in future analyses of the structures of more complex random sequence copolyesters.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.1
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• pp.44-49
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• 2011

The bio-degradable transplanting pot containing rice by-product (rice-hull and rice-bran) were developed, and tested their ability for agronomic use. Rice by-products were crosslinked with biodegradable aliphatic ally aromatic copolyesters or urea resin for making transplanting pot. Mechanical properties and degradability of these pots were measured and compared to those of the Jiffy pot (commercially used bio-degradable pot). Mechanical strength was higher than that of Jippy pot, and bio-degradability was excellent under the actual field condition. In addition, the pot could be degraded within 3 months under the ground. Our result indicated bio-degradable pot containing rice by-products has a great potential for such agronomic use.