Effect of PLA-PEO block copolymers on the compatibility of PLA/PEO blends

Miscibility of poly(lactic acid)(PLA) and poly(ethylene oxide)(PEO) was investigated by DSC, FT-IR, and SEM. The PLA/PEO blends had two melting temperatures;the one due to the PEO phase decreased as the amount of PLA was increased, while the other due to the PLA phase did not change much as PEO was added. The change in the position of the stretching vibration of the carbonyl group was negligible. AB-type diblock and ABA-type triblock copolymers of PEO and PLA were synthesized and were used as compatibilizer for PLA/PEO 60:40 blend. As PLA/PEO blends were compatibilized by either diblock or triblock copolymers, the size of the PEO domain of blends was diminished, the tensile strength was increased, and the melting point was depressed. The effect was more pronounced in blends compatibilized by diblock copolymers than those containing triblock copolymers.