Synthesis and characterization of novel polyhalogenaromatic polyimide material for electro-optic applications

Abstract

New highly fluorinated aromatic polyimide based on 4-chloro-2,5,6-trifluoro-1,3-phenylenediamine and 2,2-bis(3′,4′-dicarboxyphenyl)hexafluoropropane dianhydride was prepared by the two methods condensation in a solution followed by a high-temperature solid-state chain extension and one-pot high temperature polycondensation in a benzoic acid melt. The polyimide is soluble in polar amide- and ketone-type solvents, has good thermal stability and a high glass transition temperature. The polyimide films exhibit a low cut-off wavelength and excellent transparency in the UV-vis-near IR range. Low molecular weight prepolymer, formed by the solution condensation, was used to obtain the guest-host electro-optic polymer having a high glass transition temperature. The prepolymer layer doped with azochromophore DR1 (25wt%) was subjected to a combined poling+curing procedure upon a two-stepped heating in a corona discharge field. Nonlinear optical coefficient d33 of the prepared chromophore-doped highly halogenated polyimide film measured by the Maker fringes method is 70pm/V at the fundamental wavelength of 1064nm and remains stable up to 85°C.