Kinetics of Crystallization in Semicrystalline/Amorphous Polymer Mixtures

Abstract

The kinetics of crystallization in mixtures containing narrow molecular weight fractions of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) have been investigated as a function of the composition and molecular weight of each component and the crystallization temperature. The radial growth rates of the spherulites have been described by a kinetic equation that incorporates the cooperative diffusion coefficient, the thickness of the crystalline lamellae, and the free energy for the formation of secondary crystal nuclei. Adjusting for an apparent molecular weight dependence of the lateral and fold surface free energies of the PEO crystals permitted the construction of a master curve from the growth rate of all the mixtures studied. A precise evaluation of the equilibrium melting point of the PEO crystals in the pure polymer and in the mixtures was hindered by annealing during crystallization and heating. This latter result casts serious doubts on the determination of an interaction parameter via a melting point depression analysis in these mixtures. © 1986, American Chemical Society. All rights reserved.