Improved poling efficiency of polyurethanes containing spindle-like chromophores by a functional group tuning for nonlinear optic (NLO) materials

Novel polyurethanes NLO materials (IPDI-1 to IPDI-3) containing different spindle-like chromophores were designed and synthesized. Spindle-like chromophores (OHSTC-1 to OHSTC-4) bearing 3,4,5-trifluorophenyl, phenyl, trifluoromethylphenyl and 4-methoxyphenyl on the conjugated bridge as lateral groups, respectively, have been successfully synthesized. Selected chromophores were used as monomers to prepare polyurethane NLO materials. The chemical structure of the chromophores and polyurethanes was characterized by 1H-NMR, FT-IR and UV-Vis spectroscopy. Thermal and nonlinear optical activity characterizations of the chromophores and polyurethanes IPDI-1 and IPDI-2 were carried out. Both the chromophores and the polyurethanes NLO materials possessed relatively high thermal stability. The chromophores OHSTC-1 and OHSTC-2 displayed high thermal stability with 5% weight loss temperature (Td) as 324 °C and 327 °C, respectively. Novel polyurethanes NLO materials containing different spindle-like chromophores could be oriented without any other doped polymers and exhibited a satisfactory temporal stability in the NLO response (the electro-optic coefficients of IPDI-2 maintained up to 90% of the initial value after being baked at 85 °C in air for 200 hours).