Pockels Effects of Polyurea-5 Film Prepared by Vapor-Deposition Polymerization

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Abstract
In order to investigate the ferroelectric properties of polyurea-5 prepared by vapor-deposition polymerization in comparison with those of polyvinylidene fluoride (PVDF) and copolymers of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)), the residual polarization P r, the piezoelectric constant e 31 and the Pockels effects were measured. As a result, the P r values of polyurea-5, PVDF, and P(VDF/TrFE) were obtained as 20 mC/m2, 60 mC/m2 and 100 mC/m2, respectively. On the other hand, polyurea-5, PVDF and P(VDF/TrFE) showed e 31 of 5 mC/m2, 60 mC/m2 and 100 mC/m2, respectively. We obtained P r∼e 31 in the case of P(VDF/TrFE) and PVDF. In the case of P(VDF/TrFE) and PVDF, P r∼e 31 has been reported by many researchers. However, in the case of polyurea-5, P r>e 31 was obtained. The e 31 of polyurea-5 is about 1/20 that of P(VDF/TrFE). Also, to measure the Pockels effects of polyurea-5 films, a laser beam was introduced parallel and perpendicular to the thickness of the polyurea-5 film which was poled at room temperature. As a result, the Pockels coefficient of the polyurea-5 film was obatined to be 0.09 pm/V, which was approximately 1/4 that of PVDF or P(VDF/TrFE) films; however, this value is fairly large for polymers.