Effect of the local motions of chemical linkages on segmental mobility in poly(ester carbonate) block copolymers

A series of glassy bisphenol poly(ester carbonate) copolymers containing various linkage groups were synthesized, and the segmental motions were investigated by dynamic mechanical analysis (DMA). DMA results indicate that strong coupling exists between the motion of the cyclohexylene ring and those of neighboring segments, and the segmental mobility of the resulting polymers is thus enhanced. In contrast to the cyclohexylene ring conformational transition, the motions of terephthalate, bicyclo[2.2.1]heptane-1,4-dicarboxylate, and bicyclo[2.2.2]octane-1,4-dicarboxylate linkages are relatively independent of their environments, and therefore their incorporation does not cause much variation in polymer mobility. These results are consistent with those of a dipolar rotational spin-echo 13C NMR study,1 which show that the cyclohexylene dicarboxylate linkage is most likely to undergo the chair−boat−chair conformational transition, while the terephthalate, bicyclo[2.2.1]heptane-1,4-dicarboxylate, and bicyclo[2.2...