[en] Polyimide materials for NLO applications have attracted attentions because of their high glass transition temperature (T_g), which can be utilized to stabilize the dipole orientation of the NLO chromophore at high temperatures. Another attractive merit of polyimides is their high thermal stability that enables them to endure at elevated temperature during operation in electro-optic devices. There are two types of NLO polyimides, which have been used either as polymer hosts for composite materials or as polymer backbones for side-chain NLO chromophores. Side-chain polymer systems have the advantages such as homogeneity and high level of NLO chromophore relative to the host-guest systems, which suffer from poor homogeneity of chromophores and diffusion of the chromophores at high temperatures. The number average molecular weight (Mn) determined by gel permeation chromatography (GPC) was 23100 (M_w/M_n = 1.64) for polymer 4. The polyimide 4 was soluble in common solvents such as acetone, DMF, and DMSO, but was not soluble in methanol and diethyl ether

[en] Two approaches to minimize the randomization have been proposed. One is to use crosslinking method and the other is to use high T_g polymers such as polyimides. Polyurethane matrix forms extensive hydrogen bond between urethane linkage and increases rigidity preventing the relaxation of induced dipoles. In this work we prepared new T-type polyurethanes containing dioxynitrostilbenyl group as a NLO-chromophore. We selected 2,5-dioxynitrostilbenyl group as NLO-chromophore because it will have a large dipole moment and is rather easy to synthesize. Furthermore 2,5-dioxynitrostilbenyl group constitutes a novel T-type NLO polyurthanes, in which the NLO chromophores are parts of polymer backbones. These T-type NLO polyurethanes are not shown in the literature. After confirming the structure of the resulting polymers we investigated the properties such as T_g and second harmonic generation (SHG) activity (d₃₃). We now report the results of the initial phase of the work