Elevation of Flow Temperature and Structural Change of Poly(Lactic Acid) Gel Induced by Formation of Stereocomplex Crystals

Abstract

Poly(lactic acid) gels formed from solutions of poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA). X-ray diffraction patters indicate the formation of stereocomplex crystals for not only the gel formed from solution containing equimolar PLLA and PDLA, but also the gel formed from solution containing 9:1 of PLLA and PDLA. The flow temperatures of the gels were determined by viscoelastic measurements, and the morphologies of the dried gels were observed by field emission scanning electron microscopy. The flow temperatures of the gels from solutions containing both PLLA and PDLA were higher than those containing only PLLA. Network structures formed by uniformly distributed thin fibers, were observed for the gels formed from solutions with L:D ratios near the equimolar ratio. The dependency of the flow temperature and morphology on the polymer concentration and L:D ratio of the gels was discussed based on the experimental data.