Poly(methyl\nmethacrylate)-<i>block</i>-polyethylene-<i>block</i>-poly(methyl methacrylate) Triblock Copolymers as Compatibilizers\nfor Polyethylene/Poly(methyl methacrylate) Blends

Abstract

Poly­(methyl\nmethacrylate)-<i>block</i>-polyethylene-<i>block</i>-poly­(methyl methacrylate) (PMMA–PE–PMMA)\ntriblock copolymers were prepared by a combination of ring-opening\nmetathesis polymerization (ROMP), hydrogenation, and reversible addition–fragmentation\nchain-transfer (RAFT) polymerization. The number-average molar masses\nof the PMMA end blocks were varied (<i>M</i>_n = 1, 4, 12, and 31 kg mol^–1), whereas that of\nthe PE middle block was kept constant at <i>M</i>_n = 13 kg mol^–1. The copolymers were evaluated as\ncompatibilizers in PE/PMMA homopolymer blends containing PE in a 4:1\nexcess by weight. The compatibilized blends displayed significant\nimprovements in elastic modulus, hardness, and scratch resistance\nas compared to uncompatibilized binary blends. The effects of the\nPMMA end-block molar mass and compatibilizer concentration on the\nblend morphology and mechanical properties were investigated. The\ntriblock copolymer with the highest-molar-mass PMMA end blocks was\nmost effective, presumably because of enhanced stress transfer between\nphases by virtue of a higher degree of entanglement of the end blocks\nwith the PMMA dispersed phase.