CHAIN CONFORMATION IN POLY(VINYLIDENE CYANIDE VINYL-ACETATE) - SOLID-STATE AND SOLUTION 2D AND 3D NMR-STUDIES

D.s.c. and n.m.r. in dilute solution and in the solid state are used to study chain conformation in poly(vinylidine cyanide-vinyl acetate) [P(VDNCN-VAc)], a highly alternating piezoelectric copolymer, in order to relate the molecular and macroscopic properties. The piezoelectricity as well as the temperature and breadth of the glass transition depends strongly on the casting solvent [dimethyl sulphoxide (DMSO) versus N,N-dimethyl formamide (DMF)] for P(VDNCN-VAc) films. Solvent effects on chain conformation are measured using through-space dipolar interactions and through-bond J couplings by high resolution n.m.r. in dilute solution via 2D and 3D n.m.r. The results show that P(VDNCN-VAc) exists in a predominantly trans conformation in both DMF and DMSO solution. No solvent effects on the C-13 chemical shifts are observed in films cast from DMSO or DMF, while the molecular mobility, as measured by n.m.r. relaxation, depends strongly on the casting solvent.