Exploitation of the Strathclyde methodology in synthesizing branched vinyl polymers

Sherrington, David C. and Bouhier, Marc-Henri and Cormack, Peter A. G. and Graham, Susan. (2008) Exploitation of the Strathclyde methodology in synthesizing branched vinyl polymers. In: 235th American Chemical Society National Meeting, 2008-04-07.

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The 'Strathclyde Route' to branched vinyl polymers involves the conventional free radical soln. polymn. of a monovinyl monomer with a multi-functional monomer in the presence of an appropriate level of a chain transfer agent to suppress crosslinking. For some potential applications of branched polymers soln. polymn. would not be cost-effective. We have therefore carried out high conversion aq. emulsion copolymns. of Me methacrylate (MMA) and divinylbenzene (DVB) using sodium dodecyl sulfate as the emulsifier, potassium persulfate as the initiator and benzylthiol as the chain transfer agent. No org. solvent is employed and complete suppression of crosslinking is achieved for MMA/DVB feed mole ratios up to 5/1. 'H NMR spectroscopic and MALS/SEC analyses confirm the highly branched nature of the PMMA products which is far higher than we have been able to achieve under bulk or aq. suspension polymn. conditions. In addn. the molar mass distributions are significantly lower than those of similar materials prepd. in soln. polymns. To date we not been able to rationalise all of these exptl. findings. Early in our branching studies we realized that use of controlled polymns. might yield less broad mol. wt. distributions. We also speculated that crosslinking might be avoided, even at high conversion and without the use of a chain regulating agent, by employing a mole ratio of difunctional comonomer/initiator of ∼ 1/1, to favor statistically one branch per primary polymer chain. This proved to be so exptl. and we have now synthesized densely branched poly(Me methacrylate)s with high conversions via soln. ATR copolymn. of MMA and EGDMA. Also by employing an ATRP initiator with a discrete signature in its 'H NMR spectrum, coupled with MALS/SEC anal., very detailed evaluation of mol. structure and backbone architecture is possible. [on SciFinder(R)]