Polyoxymethylene single crystals. I. The effect of copolymer content on morphology

The single crystal morphologies of five different alkyl. capped polyoxymethylenes have been studied as a function of copolymer (ethylene oxide) content. The homopolymer produced the familiar regular hexagonal single crystal lamellae. With increasing amounts of copolymer content, however, the growth faces become much less regular and the number of overgrowths on the lamellae increases dramatically, suggesting that the copolymer chains are not incorporated as easily in the crystal. However, all crystals had crystallized into the hexagonal polyoxymethylene lattice. By the use of dark field electron microscopy significantly more terminating fringes were observed in moiré patterns from the copolymer containing crystals, indicating that the copolymer acts as a structural irregularity along the chain and leads to a defect in the lattice.