Optically Active Polyethers. 1. Studies of the Crystallization in Blends of the Enantiomers and the Stereoblock Form of Poly(epichlorohydrin)

Abstract

The isothermal crystallization kinetics and morphology of the melt-crystallized optically active polyenantiomers, their blends, and the stereoblock form of poly(epichlorohydrin) have been investigated using polarized light video microscopy. The optically active polyenantiomers develop regularly banded spherulites, while the equimolar blend and the stereoblock polymer form nonbanded, coarser spherulites. The apparent morphological differences among the polymers suggest a stereospecific segregation at the growth front in an attempt to produce optically pure lamellae. The equilibrium melting temperature as determined by the classical Hoffman-Weeks method was found to be 411 ± 1 K for all of the polymers. Over the range of crystallization temperatures from the T g (247 K) to T m °, the spherulite radial growth rates of the 50 :50 blend of the polyenantiomers are depressed relative to those of either of the optically pure components. A further marked reduction in growth rates is recorded for the stereoblock polymer. An analysis of the linear spherulite radial growth rates in terms of the Hoffman-Lauritzen treatment gave evidence of the development of larger folds, hence a rougher lamellar surface in the stereoblock polymer than in the polyenantiomers.