Polyethylene graft copolymers with a liquid crystalline component in the side chains

An ethylene-vinyl acetate copolymer (EVA) was chemically modified by the introduction of pendent thiol groups (EVA-SH) suitable for chain transfer. The resulting copolymer was grafted with 4-phenylazophenyl 4-(4-acryloyloxybuloxy)benzoate, a liquid crystalline monomer (LCM), initiated by AIBN. Grafting was performed at LCM/EVA-SH mass ratios of 10, 5, 2 and 1 in the feed. The grafting degree, i.e., the fraction of LC polymer in the graft copolymer, ranged from ca. 5-30 wt.-%. The thermal transitions were investigated by DSC, pointing at marked microphase separation between LC and polyethylene moieties. The anisotropic properties of the graft copolymers were confirmed by cross-polarized light microscopy. All the samples showed birefringence at 140 degrees C, some only on shearing however.