Polar, functionalized diene-based materials. 1. Bulk, solution, and emulsion free radical polymerization of 2-cyanomethyl-1,3-butadiene
The bulk, solution, and emulsion free radical polymerizations of 2-cyanomethyl-1,3-butadiene were studied. Traditional bulk free radical polymerization kinetics were observed, giving polymers with 〈Mn〉 values of 20×103-60×103 g/mol and polydispersities near 1.5. In solution polymerization, the highest molecular weight (82×103 g/mol at 53% conversion) was obtained in tetrahydrofuran, with a broader polydispersity attributed to chain transfer to the solvent. In these two types of polymerizations, the Diels-Alder side product yield was affected by initiator concentration, solvent concentration, and polymerization time. Emulsion polymerization gave the highest molecular weight of poly(2-cyanomethyl-1,3-butadiene) to date of 128×103 g/mol in significantly shorter reaction time than bulk or solution reactions. Finally, the polymer microstructure of approximately 95% 1,4 and 5% 4,3 structure was determined, with the percent cis-1,4 (36-45%) varying with the polymerization temperatures. The glass transition temperature of poly(2-cyanomethyl-1,3-butadiene) is near -18 °C, based on the molecular weight and the microstructure.
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