Effect of Poly (vinyl methyl ether) on the Miscibility, Crystallization and Rheology of Poly(L-lactide)/Poly (methyl methacrylate) Blends

The effect of poly (vinyl methyl ether) (PVME) on the miscibility, crystallization and rheological behavior of a 50/50 poly(L-lactide) (PLLA)/poly (methyl methacrylate) (PMMA) blend was investigated. The PLLA/PMMA blend, with compositional symmetry, was immiscible at room temperature when prepared by solution casting. However, it became miscible when heated to a high temperature, indicating an upper critical solution temperature (UCST) behavior. With the addition of PVME, whose glass transition temperature was much lower than those of PMMA and PLLA, the thermodynamic miscibility was improved for the PLLA/PMMA/PVME blend, all components being miscible at a low temperature. The crystallization kinetics of the blends was studied by observing the PLLA spherulite growth with annealing time at 100 °C via polarized optical microscopy; the addition of PVME accelerated the crystallization kinetics of the PLLA. Rheological sweep results confirmed this conclusion. The reason for this acceleration effect on the crystallization was explored by etching the PVME in the PLLA/PMMA/PVME blends. The participation of PVME in the crystallization of PLLA played a crucial role in the crystallization process.