Amorphous phase behavior and crystalline morphology in blends of poly(vinyl methyl ether) with isomeric polyesters: poly(hexamethylene adipate) and poly(ε-caprolactone)

Two isomeric polyesters, poly(1,6-hexamethylene adipate) (PHA) and poly(epsilon-caprolactone) (PCL), were each blended with amorphous poly(vinyl methyl ether) (PVME) and investigated and compared in the crystalline and amorphous phases. The amorphous phase, T(g), and crystalline morphology of the PVME/PHA blend were compared with those of classical PVME/PCL. Both blend systems exhibit a similar peculiar asymmetry with positive deviation in T(g)-composition relationships, and both are similarly miscible, with the PVME/PHA blend exhibiting chi(12)=-0.21; for PVME/PCL, chi(12)=-0.20. These values indicate that both blends are similarly miscible but have only quite weak interactions in the amorphous phase. Neat PHA shows a regime-I to -II transition, but neat PCL exhibits a regime-II to -III transition. On blending with PVME (at 20 wt%), both PVME/PCL and PVME/PHA blends undergo changes in crystallization temperature (T(c)). Dendritic spherulites in the high-T(c) (46 degrees C or above)crystallized PVME/PHA blend assume a straight-stalk pattern (chrysanthemum flower pestles or banana stems). In contrast to the similarities in amorphous-phase miscibility, the crystalline phases of these two blends differ significantly. When crystallized at high Tc (46 C or above), the PVME/PCL (20/80) blend assumes a fluffy feather-like dendritic pattern, which is dramatically different from the straight-stalk dendrites in the PVME/PHA (20/80) blend. Polymer Journal (2010) 42, 391-400; doi:10.1038/pj.2010.18; published online 24 March 2010