Spherulitic Growth in Crystalline Polymers

Abstract

The most common higher order structure of crystalline polymers is called spherulite. A spherulite is a polycrystalline aggregate densely filled with thin lamellar crystals and formed by consecutive lamellar branching and reorientation of those crystals in non-crystallographic directions. Polymer spherulites have inner structures characterized by periodic banding or patchy patterns that are created by the reorientation with correlated twisting or in random directions, respectively. The specific reorientation is related to the unbalance of surface stresses caused by the chain folding on the upper and lower basal planes of the lamellar crystals. The branching mechanism is related to the fingering instability of the growth front caused by a gradient in chemical potential ahead of the growth front. The dynamical coupling of the branching and reorientation evolves the spherulitic growth in crystalline polymers.