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 (Tg) 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 dn/dT were used to calculate the dielectric constant (ɛ), its variation with temperature (dɛ/dT), volume expansion coefficient (β) and (dβ/dT). The dn/dT and dβ/dT 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.