Synthesis, characterization, thermal stability and thermo-optical properties of poly(urethane-imide)

A novel poly(urethane-imide) (PUI) containing a diazo chromophore (dispersed red 19) in the side-chain was synthesized by a two-step process, which included preparation of diazo chromophore containing diisocyanates followed by the condensation reaction with 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). The PUI was characterized by FT-IR spectroscopy, UV–vis spectroscopy, 1H NMR, DSC and TGA. The results of DSC and TGA indicated that the PUI exhibited high thermal stability up to its glass-transition temperature ( T g ) of 196 °C and 5% heat weight loss temperature of 229 °C. The weight-averaged molecular weight ( M w ) was 52300 with a polydispersity of 2.12. The measurements of refractive indices were demonstrated at complex light and some single wavelength lights, respectively. The values of n and d n/d T were used to calculate the dielectric constant ( ɛ), its variation with temperature (d ɛ/d T), volume expansion coefficient ( β) and (d β/d T). The d n/d T and d β/d T were −4.0296 to −4.9032 × 10 −4 K −1 and 8.89–13.68 × 10 −7 K −1 (complex light), −3.9302 to −4.0981 × 10 −4 K −1 and 8.89–9.56 × 10 −7 K −1 (546–632.8 nm) respectively. The conclusion had a little significance to develop new the digital optical switch with low driving power and optical communication.