Branching Copolymerization of Styrene and Methyl Methacrylate with Divinylbenzene

Author(s):

Chun , Lin Liu , Fang , Hong Gong , Ai , Qing Lu , Wen , Yan Huang , Dan Li , Dong , Liang Zhang , Yang Yang , Bi , Biao Jiang , Jian , Hai Chen , Guang , Qun Zhai , Lizhi Kong

Message:
Abstract:
The branching copolymerization of styrene (St) and methyl methacrylate (MMA) with divinylbenzene (DVB) as branching agent was conducted using atom transfer radical polymerization (ATRP). The kinetics and extent of branching with respect to monomer convesion were studied in details. Gas chromatography (GC), proton nuclear magnetic resonance (1H NMR) spectroscopy and dual detection size exclusion chromatography (DD-SEC) were used to monitor the reactions and analyze the resulting copolymers. The analysis of reactants conversion revealed that the conversion rate of DVB, having two double bonds, is only slightly faster than those of the monomers, with no donor/acceptor interactions between DVB molecules and the monomers. The molecular weight increases slowly which is still somehow larger than the theoretical value in the early stages; then deviates significantly from the its theoretical estimation beyond 40% conversion and increases steeply at later stages of 70% monomer conversion. These results suggest that branching takes place in the early stages of the reaction regardless of any possible donor/acceptor interactions between the monomers and DVB molecules, and the coupling reaction originates mainly from the primary chain resulting in small chain branching. Coupling reaction between the branched chains becomes significant in the later stages of the copolymerization which produces highly branched chains. The reaction system contains three components throughout the reaction: the primary chains, the slightly branched chains comprising of two primary chains, and the highly branched chainsconsisting of 3 or more primary chains. Although the weight fraction of the branchedchains increases with monomer conversion, there is finally 20% primary chains stillleft in the reaction system which gives rise to limited molecular weight and highpolydispersity of the branched polymers prepared through ATRP using divinyl monomeras the branching agent.
Language:
English
Published:
Iranian polymer journal, Volume:19 Issue: 8, 2010
Page:
589
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