A Lattice Model for Interphases in Binary Semicrystalline/ Amorphous Polymer Blends. 2. Effects of Tight Fold Energy

Abstract

In a previous paper, we examined the crystal/amorphous interphase in a binary blend that is miscible in the melt but undergoes phase separation due to crystallization of one polymer in a lamellar morphology. It was assumed in these calculations that the chains were fully flexible, a situation that is not easily realizable in practice. In this paper, we extend these calculations to account for the limited flexibility of macromolecular chains, through the incorporation of an energetic parameter, En (kBT), that accounts for the reluctance of chains to assume tight fold conformations. It was found that the region of partial order for the semicrystalline component, which is essentially independent of −xab, increases slightly as one considers stiffer chains. The interphase of varying polymer composition, however, is affected strongly when bending energy effects are included, and its size increases monotonically with Eη, and inversely with −xab1/2- It is thus suggested that the interphase of partial order for the semicrystalline component is essentially pure when the interaction between the two polymers is not very strong, especially in cases where one deals with stiff crystalline polymers. However, the segments of the amorphous polymer penetrate the order -disorder interphase in cases where −xab assumes a large value. These results are apparently in agreement with recent experimental findings on poly(ethylene oxide) blends where the interphase composition is found to be dependent on the nature of the amorphous polymer in the blend. © 1991, American Chemical Society. All rights reserved.