Anisotropic rotational dynamics of rod-like low-mass molecules in polycarbonate

摘要

Comparison of the dielectric relaxation (DR) behaviors of two polar rod-like low-mass molecules (LMs), cyanobiphenyl (CB) and 5-phenyl-2,3 '-bipyridine (PBP), in antiplasticized polycarbonate (PC) revealed that rotations around the short and long axes of the LMs appeared from 60 to 125 degrees C (beta region) and from -150 to -50 degrees C (gamma region), respectively. The cooperativity between the local dynamics in PC, measured by dynamic mechanical analysis, and the rotation of the LMs around the short axis was examined based on the relaxation times and activation energies for the LMs (CB and PBP) and PC. The dynamic cooperativity involved the antiplasticization of PC. In contrast, the rotation of the LM (PBP) around its long axis was independent of the local motion in PC, resulting in no contribution to the antiplasticization phenomenon. Adding rod-like low-mass molecules (LMs) increases the elastic modulus of polycarbonate (PC). The anisotropy of the rotational dynamics of rod-like LMs in PC was investigated by dielectric relaxation and dynamic mechanical analysis. Two rotations of the LM around the short and long axes were separately observed at 80 degrees C and -100 degrees C, respectively. The rotation of the LM around the short axis was cooperative with the local dynamics of PC and. In contrast, the rotational motion around the long axis was independent of PC motions.