Crystallization of precisely halogen-substituted polyethylenes induced by ultra-high molecular weight polyethylene fiber

The precisely halogen-substituted polyethylenes prepared by ADMET polymerization, that is, PE21F, PE21Cl and PE21Br were chosen as substituted polymers model to study the epitaxial crystallization of substituted polymers induced by the UHMWPE fiber. The morphology, structure and melting behavior of the crystals were characterized by SEM, WAXD and DSC, respectively. The results showed that ribbon crystals with molecular chains parallel to the fiber axis formed on the UHMWPE fiber surface, and the size and regularity decreased with the increase of substituent volume. PE21F with a small substituent could be induced to form two-component crystals on the UHMWPE fiber surface. However, when the substituent volume increased to Cl and Br, the order of crystal formed on the fiber surface was relatively low, which could not induce the crystallization of peripheral molecules. The melting temperatures of the crystals formed on fiber were much higher than that of the bulk polymers, which was attributed to more ordered crystal structure and the thicker lamellae induced by the UHMWPE fiber. In addition, we also discussed the influence mechanism of different structural characteristics and chemical composition of fillers on the crystallization behavior of substituted polymers. This study will establish a better understanding of interface-induced crystallization.