Stereocontrol in radical polymerization of N,N-dimethylacrylamide and N,N-diphenylacrylamide and thermal properties of syndiotactic poly(methyl acrylate)s derived from the obtained polymers

Free-radical polymerizations of N,N-dimethylacrylamide (DMAA) and N,N-diphenylacrylamide (DPAA) were carried out under various conditions. DMAA gave an isotactic-rich polymer in most cases, whereas DPAA gave a syndiotactic polymer. The polymerization stereochemistry was also affected by reaction solvents including toluene, tetrahydrofuran, and fluoroalcohols. It is notable that the stereochemistry of the polymerization depended on monomer concentration: a lower monomer concentration led to a higher isotacticity for DMAA polymerization and a higher syndiotacticity for DPAA polymerization. This effect was explained by assuming that there exist two types of growing radicals having different stereoselectivities. By optimizing the aforementioned reaction conditions, poly(DMAA) with diad isotacticity im) of 77% (polymerization in toluene at -78 degreesC at [M](o) = 0.1 M) and poly(DPAA) with diad syndiotacticity (r) Of 93% (polymerization in THF at -98 degreesC at [M](o) = 0.22 M) were obtained. Stereoregular poly(methyl acrylate)s were derived from the Doly(DPAA)s. Thermal property of the poly(methyl acrylate)s with different tacticities was studied by DSC.