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

• Published in: Polymer (Guilford) Vol. 54; no. 24; pp. 6608 - 6616
• Main Authors: Liu, Gengxin, Ma, Hongwei, Lee, Hyojoon, Xu, Hongde, Cheng, Shiwang, Sun, Hao, Chang, Taihyun, Quirk, Roderic P., Wang, Shi-Qing
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 14.11.2013; Elsevier
• Subjects: Applied sciences; Branch polymers; engineering; Exact sciences and technology; Melt stretching; molecular weight; Organic polymers; Physicochemistry of polymers; Polymerization; polystyrenes; Preparation, kinetics, thermodynamics, mechanism and catalysts; Rheology; spatial distribution; Melt stretching; Branch polymers; Rheology; Strain rate sensitivity; Tensile stress; Stress relaxation; Molten state; Branched polymer; Stress strain relation; Long chain; Preparation; Anionic polymerization; Styrene polymer; Experimental study; Rheological properties
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2013.10.007

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 λ = 7.4, the specimen would not undergo elastic breakup that occurs in linear PS even at λ = 2.7. These LCB-PSs are also extraordinarily more stretchable during startup uniaxial extension, with the maximum engineering stress emerging at stretching ratio λmax≈4Mbb/Me, where Mbb is the molecular weight of backbone and Me is the molecular weight between entanglements. [Display omitted]