Long-chain branched polymers to prolong homogeneous stretching and to resist melt breakup

We explored a new synthetic strategy for ultra-high molecular weight long-chain branched (LCB) polymers with equal spacing between adjacent branch points. This method can synthesize LCB polystyrene (LCB-PS) with total molecular weight of 4.9 million g/mole, 16 branches of 140 kg/mole and polydispersity index of 1.5. The introduction of multiple branch points with long side chains allows the LCB-PS to resist the elastic-driven decohesion. Even after a large step extension of stretching ratio lambda = 7.4, the specimen would not undergo elastic breakup that occurs in linear PS even at lambda = 2.7. These LCB-PSs are also extraordinarily more stretchable during startup uniaxial extension, with the maximum engineering stress emerging at stretching ratio lambda(max) approximate to 4 root M-bb/M-e, where M-bb is the molecular weight of backbone and M-e is the molecular weight between entanglements. (C) 2013 Elsevier Ltd. All rights reserved.