1H–13C Nuclear Cross-Relaxation and Molecular Motion in Single Crystalline Film of Vinylidene Fluoride and Trifluoroethylene Copolymer with 75 mol% Vinylidene Fluoride

Abstract

1H–13C nuclear cross relaxation and molecular motion in a highly double-oriented film of vinylidene fluoride (VDF) and trifluoroethylene (TrFE ) copolymer with 75 mol% VDF were studied using the cross-polarization/magic angle spinning nuclear magnetic resonance technique. A transient oscillation was observed in the 13C peak intensity vs. contact time plots for the CH2, CHF and CF2 groups. Based on the cross relaxation theory of the spin diffusion 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 T1ρH in the rotating frame in both domains showed the two T1ρH minimum processes of β and αb 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 the T1ρH minimum process of α1D is due to the one-dimensional diffusion motion of the conformational defects along the chain, accompanied by the trans and gauche transformations of the VDF conformers in the paraelectric phase on cooling. The anomaly of the T1ρH minimum at the Curie temperature depended on the conformational stability of both segments. The deflected trans TrFE segment did not experience any conformational change in the transition region, in contrast to the trans-gauche conformational change in the VDF segment.