Polar, functionalized diene-based materials. V. Free-radical polymerization of 2-[(N-benzyl-N-methylamino)methyl]-1,3-butadiene and copolymerization with styrene
2-[(N-Benzyl-N-methylamino)methyl]-1,3-butadiene (BMAMBD), the first asymmetric tertiary amino-containing diene-based monomer, was synthesized by sulfone chemistry and a nickel-catalyzed Grignard coupling reaction in high purity and good yield. The bulk and solution free-radical polymerizations of this monomer were studied. Traditional bulk free-radical polymerization kinetics were observed, giving polymers with values of 21 × 103 to 48 × 103 g/mol (where Mn is the number-average molecular weight) and polydispersity indices near 1.5. In solution polymerization, polymers with higher molecular weights were obtained in cyclohexane than in tetrahydrofuran (THF) because of the higher chain transfer to the solvent. The chain-transfer constants calculated for cyclohexane and THF were 1.97 × 10-3 and 5.77 × 10-3, respectively. To further tailor polymer properties, we also completed copolymerization studies with styrene. Kinetic studies showed that BMAMBD incorporated into the polymer chain at a faster rate than styrene. With the Mayo-Lewis equation, the monomer reactivity ratios of BMAMBD and styrene at 75°C were determined to be 2.6 ± 0.3 and 0.28 ± 0.02, respectively. Altering the composition of BMAMBD in the copolymer from 17 to 93% caused the glass-transition temperature of the resulting copolymer to decrease from 64 to -7°C.
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