Nonbirefringent bands in thin films of a copolymer melt: rapid rhythmic crystal growth with an unusual crystal–melt interface

Abstract

A fascinating phenomenon of nonbirefringent bands that are comprised of repetitive stacks of discrete lamellae with a nearly flat-on orientation along the growth directions is first reported in a thin film of an asymmetric poly(ε-caprolactone)-b-poly(ethylene oxide) during isothermal melt crystallization. More specifically, excepting the rapid growth kinetic of nonbirefringent banded crystals, in situ observations disclose an intriguingly wide halo adjacent to the depletion zone in the crystal–melt interface, implicating the presence of long range mass transfer that is a premise for the occurrence of micrometer-scale rhythmic crystallization.