Novel Nonlinear Optic Polymers with Thermal Stability

Abstract

We have synthesized and evaluated nonlinear optical (NLO) properties of azo dye attached novel NLO polymers with high optical nonlinearity and/or high thermal stability. An azo-dye attached NLO polymer with a furan derivative as an acceptor was synthesized. The second order NLO susceptibility (χ(2) 33) at 1.3 μm fundamental wavelength was more than two times larger than that of the NLO polymer with dicyanovinyl (DCV) acceptor and the same azobenzene structure. A χ (2) 33 of 43pm/V was obtained. Polymethacrylic acid reacted with a typical azo dye, Disperse Red 1 dye (DR-1), in its side-chain was also synthesized using a new approach, i.e., via intermediate reaction of the acid and N,N'- dicyclohexylcarbodiimide. Glass transition temperatures Tg of 170°C were obtained for the dye attached polymethacrylic acid with the DR- 1 contents of 29 mol%. A χ (2) 33 of 53pm/V at 1.3 μm was obtained. This polymer can be further improved to have more stablility by heat treatment. Through this treatment, the methacryl imide structure was formed and the polymer has Tg of 165°C. This imidized polymer exhibited a χ (2) 33 of 45 pm/V at 1.3 μm and maintained about 90% of its initial value after 230 hours or more at 100°C. Novel NLO polyarylethers where electron-withdrawing groups for NLO activity were introduced into the polymers by post-functionalization were developed. These NLO polyarylethers have high Tgs, typically higher than 200°C. A 100 mol% DR-1 dye containing NLO polymer with the fluorene structure has very low optical propagation loss of 0.42dB/cm at 1.3 μm wavelength and shows low polarized light dependence of the refractive indices. The polymer has χ (2) 33 of about 57pm/V at 1.3|um fundamental wavelength and the nonlinearity was maintained at 100°C for more than 200 hrs Key words: second order nonlinear optics, nonlinear optical polymers, thermal stability, furan derivative, polymethacrylic acid, azo dye, imidization, polyarylether