Pyroelectric polymer films

Abstract

The objective of this investigation was to synthesize polymeric materials of high pyroelectric efficiency and to prepare thin test films suitable for use in pyroelectric vidicons. In our investigation of vinyl-addition polymers with highly polar pendant groups, we concentrated on atactic and isotactic substituted styrenes. Five atactic 4-substituted styrenes, poly(4-bromostyrene), poly(4-nitrostyrene), poly-(4-chlorostyrene), poly(4-methoxystyrene) and poly(4-fluorostyrene), were synthesized and evaluated, as were four isotactic 4-substituted styrenes, poly(4-bromostyrene), poly(4-chlorostyrene), poly(4-methoxystyrene) and poly(4-fluorostyrene). Hot-pressing was found to be a successful method of fabricating thick films of those polymers which did not undergo thermal decomposition near the melting point. Solvent casting of polymer films directly onto the test substrate proved to be the only practical method of handling brittle thin polymer films. Film formation by stretching and blowing was not found to be suitable for most of the polymers investigated. Laser evaporation was found to be a very useful technique for the preparation of polymer test films. Laser-evaporated poly(vinyl fluoride) showed the highest known pyroelectric coefficient for this material (1.8×10 -9C/cm 2 °K). None of the poly(4-substituted styrenes) showed any substantial pyro-electric behavior. This result can be attributed to their characteristics helical structure and lack of net permanent dipole moment.