H-1-C-13 nuclear cross-relaxation and molecular motion in single crystalline film of vinylidene fluoride and trifluoroethylene copolymer with 75 mol%vinylidene fluoride

H-1-C-13 nuclear cross relaxation and molecular motion in a highly double-o riented film of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copo lymer with 75 mol% VDF were studied using the cross-polarization/magic angl e spinning nuclear magnetic resonance technique. A transient oscillation wa s observed in the C-13 peak intensity vs. contact time plots for the CH, CH F and CF, groups. Based on the cross relaxation theory of the spin diffusio n process, it was clarified that the oscillation behavior was caused by the TrFE-rich domain and that the crystal consisted of VDF-rich and TrFE-rich domains, The spin-lattice relaxation time T-1pH in the rotating frame in bo th domains showed the two T-1pH minimum processes of beta and alpha (b) in the ferroelectric phase, which are respectively due to the flip-flop motion of the TrFE segment and the oscillational motion of the VDF segment, and t he T-1pH minimum process of alpha (1D) is due to the one-dimensional diffus ion motion of the conformational defects along the chain, accompanied by th e trans and gauche transformations of the VDF conformers in the paraelectri c phase on cooling. The anomaly of the T-1pH minimum at the Curie temperatu re depended on the conformational stability of both segments. The deflected trans TrFE segment did not experience any conformational change in the tra nsition region, in contrast to the trans-gauche conformational change in th e VDF segment.