| Abstrakt: |
The heterogeneous higher order structure and molecular motion in a single crystalline film of a vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer with 73 mol % VDF was investigated with the 1H13C cross-polarization/magic-angle spinning NMR technique. A transient oscillation was observed in plots of the 13C peak intensity versus the contact time for the CH2, CHF, and CF2 groups. On the basis of the extended cross-relaxation theory of spin diffusion, we determined that the oscillation behavior was caused by the TrFE-rich segments in the chain and that the crystal consisted of VDF-rich and TrFE-rich domains. The former had TrFE-rich segments in VDF and TrFE fractions of 0.24 and 0.27, respectively, and the latter had VDF-rich segments in a VDF fraction of 0.49. The spinlattice relaxation time T1ρH in the rotating frame for each group was minimal in the three temperature regions of β, αb, and αc (↑) on heating and in the two temperature regions of α1D and αc (↓) on cooling. The αc (↑) and αc (↓) processes depended on the first-order ferroelectric phase-transition regions on heating and cooling, respectively. The motional modes for the other processes were confirmed by the T1ρH minimum behavior of the VDF and TrFE groups in the TrFE-rich domain and the VDF-rich segments in the VDF-rich domain. The β and αb processes were attributed to the flipflop motion of the TrFE-rich segments and the competitive motion of the TrFE- and VDF-rich segments in the ferroelectric phase, respectively. The α1D process was due to the one-dimensional diffusion motion of the conformational defects along the chain in the paraelectric phase, accompanied by the trans and gauche transformation of the VDF conformers of ttg+tg− and g+tg−tt. The effect of the competitive motion of the TrFE-rich segment on the thermal stability of the VDF-rich segment in the chain near the Curie temperature was examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 10261037, 2002 |
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