Molecular modeling studies on high-strain, electrostrictive terpolymers

The finding that irradiation of copolymer films serves to break up the large crystalline regions into polar microregions resulting in a high-strain electrostrictive material has prompted an investigation to identify alternative routes to electrostriction. To determine whether these changes could be reproduced without the need for electron-irradiation, computations on (PVDF-TrFE) terpolymer chains containing small levels a third monomer incorporating chlorine have provided a theoretical framework to support the hypothesis that the introduction of chlorine in the polymer chain can produce similar structural defects that disrupt the polar all-trans regions into smaller regions. These calculations demonstrate that polar nano-regions can be created since introduction of bulky chlorine atoms into the polymer chains creates conformational defects that provide the mechanism to break up the long-range crystalline regions. The disrupted polar regions can be regarded as distorted defect structures that give rise to random fields and electrostriction. Theoretical predictions as well as experimental support will be presented that show that certain chloro-monomers such as -CFCl-CH₂- are indeed quite able to convert P(VDF-TrFE) films into high-strain, electrostrictive films.