期刊
POLYMER
卷 49, 期 11, 页码 2656-2661出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2008.04.014
关键词
poly(L-lactic acid); stereoblock polylactide; solid-state polycondensation
Stereoblock poly(lactic acids) (sb-PLAs), having abundant enantiomeric compositions of poly(L-lactic acid) (PLLA), were successfully synthesized by solid-state polycondensation (SSP) of the melt blends of medium molecular weight prepolymers: both PLLA and poly(D-lactic acid) (PDLA) that had primarily been prepared by melt-polycondensation. The molecular weight of the resultant PLLA-rich sb-PLA was effectively enhanced by the dehydrative coupling of abundant PLLA molecules followed by the increase in homo-chiral crystallinity. These sb-PLA were successfully fabricated into polymer films by solution casting to analyze their crystalline morphology and properties. Both DSC and WAXS revealed preferential stereocomplexation in spite of concomitant homo-chiral crystallization for these sb-PLA. Particularly, exclusive sc crystallization was observed with melt-quenched sb-PLA represented whose PDLA ratio was above 15%. Therefore, the stereoblock structure can suppress the homo-chiral crystallization and increase the sc crystallinity even with the non-equivalent PLLA/PDLA compositions. Their thermal resistivity up to 200 degrees C was supported by the dynamic mechanical analysis of the sb-PLA films. (c) 2008 Elsevier Ltd. All rights reserved.
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