Chain Packing at Polymer Interfaces

Abstract

The lattice theory presented in the preceding paper is applied to various polymer interfaces of general interest. The reduction of surface chain density in lamellar semicrystalline polymers due to tilting of the interfacial plane from orthogonality to the chain sequences within the crystal allows the incidence of adjacent folds to diminish markedly; it may become negligible for a tilt angle > 25°. Chain configurations in the noncrystalline region between two lamellar crystallites are little affected by the entry of chain sequences from the more remote surface if the interlamellar separation is greater than 4-5 lattice layers, or ca. 20 A. In lamellar single crystals, the sites of chain reentry are separated predominantly by two or three lattice steps, according to the theory. For polymer melts bounded by a hard wall, the theory predicts a rather narrow interphase comprising no more than two lattice layers. The chain sequences tend to orient along the surface in the first layer adjoining the wall, whereas in the second layer they exhibit a slight preference for orientation normal to the surface. Similar characteristics of chain configurations hold for a thin layer between two walls, or in a thin film, unless the thickness approaches that of a monomolecular layer. © 1984, American Chemical Society. All rights reserved.