• Macromolecular Research
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• v.14 no.5
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• pp.510-516
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• 2006

Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups. For optimization of the reaction conditions, the effects of temperature, pressure, PLA molecular weight, and catalyst type on the lactide synthesis were examined. The fraction of D,L-lactide decreased with increasing temperature. Among the various Sn-based catalysts, the D,L-lactide fraction was maximized when SnO was used. A higher yield with lower racemization was observed at lower pressure. The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca. 1380. The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight. The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%. The lactide was more sensitive to racemization because of the entropic effect.

• Journal of Environmental Science International
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• v.23 no.3
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• pp.473-481
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• 2014

Poly(lactide)s(PLA) is an attractive material to solve the problem of waste plastic accumulation in nature because of its biodegradability. The lactide exists in three stereoisomeric configurations: L-lactide, D-lactide, and meso-lactide. PLA stereocomplexes, formed by the mixing of two enantiomers, poly(L-lactide)(PLLA) and poly(D-lactide)(PDLA), have many favorable characteristics because the stereocomplex showed $50^{\circ}C$ higher melting point than each enantiomeric polymer and the resistance toward degradation increased. In this study, we investigated the influence of the composition and the optical purity of each component on the formation of stereocomplexes. Also, the nanofibers of stereochemical PLA and their blends were prepared by electrospinning method. The properties of the obtained fibers were analyzed by differential scanning calorimetry and scanning electron microscopy. The results showed that a degree of stereocomplex was controlled by change of optical purity of each component. The enzymatic degradation of the fibers were strongly dependent on the stereocomplex.