Effect of a small amount of poly(ethylene oxide) on crystal polymorphism of poly(l-lactic acid)

Poly(l-lactic acid) (PLLA) is a biodegradable and biocompatible polyester with great promise to be used in biomedical fields. Blending with poly(ethylene oxide) (PEO) can further improve the biocompatibility of PLLA. In this work, the effect of miscible blending of PEO on the crystal structure of PLLA was investigated. For neat PLLA, α′- and α-crystals are formed at crystallization temperature Tc < 110 °C and Tc ≥ 110 °C, respectively. With increasing PEO content, the difference of lattice spacing between α′- and α-crystals is gradually reduced. As PEO reaches 10 wt%, there is no apparent evidence of the presence of α′-crystal in the investigated Tc ranges. The blending effect of PEO on the crystal polymorphism of PLLA can be ascribed to the declined equilibrium melting point and lowered glass transition temperature.