Configurational Entropy and Polymer Miscibility: New Experimental Insights From Solid-State NMR

Abstract

Entropy is generally discounted as a driving force for macromol. mixing, due to the vanishing combinatorial component in the Flory-Huggins treatment. However, recent chain-level investigations in blends of high mol. wt. polyolefins suggest that configurational entropy must be considered, particularly for amorphous macromols. lacking any chem. functionality. Multinuclear one- and two-dimensional solid-state NMR techniques were used to interrogate the dynamics and mixing length scales in blends contg. polyisobutylene and either head-to-head polypropylene or polyethylene-co-butene. These polymer systems have no chem. heterogeneity that would facilitate miscibility through enthalpic contributions; exptl. results prove that there is a quantifiable increase in configurational entropy. In addn., exptl. evidence from polyolefin blends regarding the length-scale and time-scale of the polymer glass transition is discussed. Editor(s): Webb, Graham A. Publisher: Springer, Dordrecht, Neth