Abstract: Four novel poly(urethane imide)s(PUIs) containing a diazo nonlinear optical chromophore in the side chain were synthesized by a two step process, which includes preparation of diazo chromophore containing diisocyanates followed by the condensation reaction with dianhydrides. The PUIs obtained were characterized by FTIR spectroscopy, UV-Vis spectroscopy, DSC and TGA. All PUIs exhibit a maximum UV-Vis absorption of the diazo chromophore at the wavelength of about 490 nm. They are soluble in aprotic solvents such as NMP, DMAc, DMF, DMSO and 1,4-butyrolactone. Some are even soluble in common low boiling point solvents such as THF. The high organo solubility of PUIs results from the existence of the flexible urethane moiety in the backbone and a side chain chromophore, which leads to loose chain packing and enlarge free volume. The intrinsic viscosities of PUIs are 0.16~0.31 dL/g. The PUIs possess glass transition temperatures( T_g) at 171~211 ℃, which are much higher than the corresponding side chain nonlinear optical(NLO) polyurethanes. PUIs based on 4,4′-(hexafluoroisopropylidene) diphthalic anhydride(6FDA) and tolulene 2,4-diisocyanate(TDI) possess higher T_g than those based on 3,3′ , 4,4′-diphenylether-tetracarboxylic acid dianhydride(OPDA) and methylenediphenylene diisocyanate(MDI). Two steps of weight loss are found in TGA curves of PUIs. The initial decomposition temperatures of PUIs are around 300 ℃, which is attributed to the thermal decomposition of the urethane moiety and the side chain chromophore.

Key words: Poly(urethane-imide), Side chain, Second-order nonlinear optics, Synthesis, Characterization