• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1028-1034
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• 1999

Poly(lactic acid) is expected to be one of the most promising biodegradable polymers. However, the high molecular weight polymer could be obtained by ring-opening polymerization process conventionally, which raises the production cost and decreases the final yield. In this study, linear and star-shaped poly(L-lactic acid)s were prepared by direct solution polycondensation method and their physical and thermal properties were examined. Tin compounds were found to be effective catalyst for the preparation of high molecular weight polymers. When 0.2g (0.5 wt % of monomer) of $SnCl_2$ and 100 mL of p-xylene were used, the polymer yield and molecular weight were relatively high. As a means to obtain higher molecular weight polymer easily in the direct polycondensation system, dipentaerythritol(dipet) or pentaerythritol(pet) was introduced as a multifunctional branching monomer to provide a star-shaped poly(lactic acid). Moderately high molecular weight polymers with the inherent viscosity values up to 1.14 dL/g(weight-average molecular weight of about 140000 by GPC) were obtained and could be cast strong and transparent films.

• KSBB Journal
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• v.16 no.5
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• pp.505-510
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• 2001

The preparation, characterization and drug release behaviour of drug(indomethacin) loaded Poly(L-lactic acid)(PLA), tarmarind acetate and levan acetate mircospheres were investigated. Hydrophobic tarmarind acetate and levan acetate were prepared by chemical modification of hydrophilic tarmaried gum and levan and microspheres were made by a solvent evaporation method. In the case of poly(L-lactic acid) microspheres, drug release rate was effected by polymer-drug ratios and drum release was sustained by increasing of polymer content. The yield of microspheres were effected by many factors and the mean size was below 1 $\mu$m, The IND release profiles from tarmarind acetate and levan acetate micropheres were more slightly less than ploy(L-lactic acid) microspheres.

• Fibers and Polymers
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• v.4 no.2
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• pp.59-65
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• 2003

PLA/LPCL/HPCL blends composed of poly(lactic acid) (PLA), low molecular weight poly($\varepsilon$-caprolactone) (LPCL), and high molecular weight poly($\varepsilon$-caprolactone) (HPCL) were prepared by melt blending for bioabsorbable fila-ment sutures. The effects of blend composition and blending time on the ester interchange reaction by alcoholysis in the PLA/LPCL/HPCL blends were studied. Their thermal properties and the miscibility due to the ester interchange reaction were investigated by $^1{H-NMR}$, DSC, X-ray, and UTM analyses. The hydroxyl group contents of LPCL in the blends decreafed by the ester interchange reaction due to alcoholysis. Thus, the copolymer was formed by the ester interchange reaction at $200^{\circ}C$ for 30-60 minutes. The thermal properties of PLA/LPCL/HPCL blends such as melting temperature and heat of fusion decreased with increasing ester interchange reaction levels. However, the miscibility among the three poly-mers was improved greatly by ester interchange reaction. Tensile strength and modulus of PLA/LPCL/HPCL blend fibers increased with increasing HPCL content, while the elongation at break of the blend fibers increased with increasing LPCL content.

• Polymer(Korea)
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• v.26 no.5
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• pp.582-588
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• 2002

The block copolymers were prepared by the ring opening polymerizati on of DL-lactide by poly(ethylene oxide) (PEO) with diethylzinc (ZnE$_2$) as a catalyst. When the feed ratio of PEO was over 30% relative to DL-lactide, the polymerization of DL-lactide took place from the PEO hydroxyl terminals to provide the desired A -B-A or A-B block copolymer. The block copolymers were made of films by cast method and the films obtained was drawn to 2.5 times at 60 $\^{C}$. At the same draw ratio, the tensile modulus of the films was decreased with increasing PEO content in the block copolymers. It was therefore suggested that the block copolymers comprising of PDLLA and PEO, had high potentials as the biomaterials with improved flexibility.

• Journal of Pharmaceutical Investigation
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• v.34 no.5
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• pp.401-406
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• 2004

To develop an intravenous delivery system of all-trans retinoic acid (ATRA) for the cancer therapy, poly(L-lactic acid) nanoparticles were prepared and characterized. Emulsification-solvent evaporation method was chosen to prepare submicron sized nanoparticles. Spherical nanoparticles less than 200 nm in diameter with narrow size distribution were prepared, and the entrapment efficiency of drug was more than 95%. The endothermic peak at $183^{\circ}C$ and X-ray crystallographic peak of ATRA appeared in the nanoparticle system, suggesting the inhibition of crystallization of ATRA by polymer adsorption during the precipitation process. ATRA was released at $37^{\circ}C$ for 60 days and the release rate was dependent on the concentration of drug incorporated in the nanoparticles. While ATRA was unstable in the light, it was very stable at $4^{\circ}C$. These results suggest the usefulness of PLA nanoparticles as a sustained and prolonged release carrier for ATRA.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.95-102
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• 2023

Despite the easing of social distancing, demand for non-face-to-face services continues to rise. Recently, the EU is pursuing a comprehensive plastic use reduction by expanding the scope of plastic use regulations for packaging plastics according to the New Cyclical Economy Action Plan(NCEAP). In response to this trend, the packaging industry is moving away from conventional non-degradable/petroleum-based plastics and conducting research on packaging materials using biodegradable plastics such as PLA(Poly Lactic Acid), PBAT(Poly Butylene Adipate-co-butylene Terephthalate). On the other hand, ginkgo leaves occur in large quantities in Korea and act as a cause of slip accidents and flooding. In this study, a method to utilize ginkgo biloba leaf as a new alternative biomass resource was proposed by producing lactic acid through pretreatment, enzymatic saccharification, and fermentation processes. For the efficiency of lactic acid production, a comparative analysis of lignin content from before and after browning was performed. In addition, the degree of glucan extraction was evaluated by applying a pretreatment method using three catalysts: hot water, sulfuric acid, and sodium hydroxide. It is difficult to expect high production of lactic acid with single process. Therefore, an integrated process operation using both the pretreated hydrolyzate and the residual solid enzymatic saccharification solution must necessarily be applied.

• Fiber Technology and Industry
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• v.12 no.3
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• pp.169-179
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• 2008

• YAKHAK HOEJI
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• v.44 no.4
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• pp.293-299
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• 2000

Biodegradable microspheres made from poly-lactide-co-glycolide polymers have been considered as a new delivery system for single-dose vaccine. Purified tetanus toxoid (TT) was encapsulated in poly-lactide(PLA) and poly-lactide-co-glycolide (PLGA) microparticles using a solvent evaporation method in a multiple emulsion system (water-in oil-in water). The morphology of 77-loaded microparticles was spherical and the suface of them was smooth. The particle size was in a range of 2-10. Protein loading efficiency was 68-97.8%. PLGA (85:15) microparticle showed the highest efficiency. Protein release pattern was influenced by polymer molecular weight and composition. The release rate of PLA(Mw 100,000) microsphere was higher than any other microspheres. In consequence of the hydrolysis of PLGA(50:50) microspheres, environmental pH decreased from 7.4 to 5.0. The PLA, PLGA (75:25) and PLGA (85:15) microshperes showed no significant pH change. The antigenicity or n in microshperes was assayed by indirect sandwich ELISA using equine polyclonal tetanus antitoxin for capture antibody and human polyclonal tetanus antitoxin for primary antibody. The antigenicity of TT in PLA (Mw 100,000), PLGA(50:50, Mw 100,000) and PLGA (75:25, Mw 73,300) after 30 days incubation showed 54, 40.9 and 76.7%, respectively.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.711-712
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• 2005

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.622-624
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• 2003

Poly(lactic acid) is a biodegradable themoplastic based on the renewable resources to substitute for petrochemical plastics. Most of PLA is produced by ring opening polymerization from lactide. However, pyrolysis process in the lactide synthesis is expensive, we studied lactide synthetic process for more economical preparation of PLA. In this research was tried to minimize the pyrolysis time, and obtained L-lactide from lactic acid without any catalyst.