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-diphe nylacrylamide (DPAA) were carried out under various conditions. DMAA gave a n isotactic-rich polymer in most cases, whereas DPAA gave a syndiotactic po lymer. The polymerization stereochemistry was also affected by reaction sol vents including toluene, tetrahydrofuran, and fluoroalcohols. It is notable that the stereochemistry of the polymerization depended on monomer concent ration: 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 radi cals having different stereoselectivities. By optimizing the aforementioned reaction conditions, poly(DMAA) with diad isotacticity im) of 77% (polymer ization in toluene at -78 degreesC at [M](o) = 0.1 M) and poly(DPAA) with d iad syndiotacticity (r) Of 93% (polymerization in THF at -98 degreesC at [M ](o) = 0.22 M) were obtained. Stereoregular poly(methyl acrylate)s were der ived from the Doly(DPAA)s. Thermal property of the poly(methyl acrylate)s w ith different tacticities was studied by DSC.