Critical Behaviors of the NMR Line Width in Vinylidene Fluoride and Trifluoroethylene Copolymers near T_c : Electrical Properties of Condensed Matter

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NMR line widths in VDF/TrFE copolymers with VDF 65 and 52 mol.% were measured as a function of the alignment angle γ between the drawn axis and the magnetic field over a temperature range from 20 to 130℃ and the results were compared with those for VDF 72 mol.% copolymer. In the cooling process, a slight increase was observed on the line width for each copolymer near the Curie temperature T_c, which depended on the angle γ. This finding was explained by applying the effective Ising model to the configuration fluctuation of the trans segments. The anomalous part of the line width, ΔH_<fluc> with the form of T^2(T-T_0)^<-1/2> was derived. Using the experimental values of ΔH_< fluc> for each copolymer, the effective nearest-neighbor distance, d, between fluctuating trans segments, and the correlation length, ξ, were calculated. Both the values of d and ξ became larger in the order of 72, 52 and 65 mol.%. The magnitude of ξ for each copolymer was very close to the average distance, r (=5.9 A), between the fluctuating order units. The contribution of ξ to the polarization fluctuation was discussed by comparing the results which had been obtained from the spin-lattice relaxation time measurement.
社団法人応用物理学会の論文
1988-06-20