PECULIARITIES OF DIPOLE-SEGMENTAL MOBILIT Y IN AROMATIC POLYIMIDES

Dipole-segmental mobility of aromatic polyimides based on a dianhydrid e of 3,3',4,4'-diphenyloxide of tetracarboxylic acid and diamines of 4 ,4'-oxydianiline (DPO), 4,4'-diaminediphenyl ether of resorcinol (RD), and 4,4'-diaminodiphenyl ether of diphenylolpropane (AD) was studied by the thermally stimulated depolarization current, methods and measur ements of electric conductivity and dielectric relaxation methods. The softening temperatures of these polyimides were estimated to be 252, 219, and 212-degrees-C, respectively. Decrease in heat resistance is s hown to be accompanied by a growth in activation energy of segmental m obility as determined by the dielectric relaxation method (5.5, 6.5, a nd 7.8 eV, respectively). The temperature dependences of quasiequilibr ium activation thermodynamic functions of segmental mobility, as deter mined by the thermally stimulated depolarization current method, allow ed calculations of the lengths of kinetic segments as well as dimensio ns and phenomenological parameter of order of the regions of associate d motion of segments of polyimide macromolecules. As compared with RD, supermolecular organization of AD appeared to be less ordered. The co rresponding kinetic segment is half that of RD, and hence AD possesses a more developed physical network.