کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5187151 | 1381122 | 2008 | 6 صفحه PDF | دانلود رایگان |
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 °C was supported by the dynamic mechanical analysis of the sb-PLA films.
Journal: Polymer - Volume 49, Issue 11, 27 May 2008, Pages 2656-2661