Miscibility in blends of stereoregular poly(methyl methacrylate)/poly(ethylene oxide) based oligomers

The miscibility of blends of poly(methyl methacrylate), PMMA, and poly(ethy lene oxide), PEO, oligomers was studied by temperature-modulated DSC as a f unction of the PMMA stereoregularity, the molecular weight and the nature o f the chain ends of the PEO. The Flory-Huggins interaction parameter chi (1 .2) was determined using the methodology developed by Kim and Bums and comp ared to those calculated from the Hildebrand solubility parameters drawn fr om the Van Krevelen tables. First, it turns out that the miscibility domain is larger for the a- and s-PMMA than for the isotactic isomer (as shown in previous studies) and, moreover, larger for butyl terminated PEO oligomers . The Flory-Huggins interaction parameter chi (1.2) decreases with the incr ease of the PEO molecular weight as well as with the syndiotacticity of the PMMA and is lower for the PEO with alkyl modified chains ends. These resul ts highlight the non negligible contribution of the free volume to the inte raction parameter and also the importance of the kinetic of the PEO crystal lisation on the phase separation process. (C) 2001 Published by Elsevier Sc ience Ltd.