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Synthesis and properties of novel nonlinear optical polyurethane containing 4-(2′-carbomethoxy-2′-cyano)vinyl-5-nitrocatecholic group

ABSTRACT A new X-type polyurethane (5) containing 4-(2′-carbomethoxy-2′-cyano)vinyl-5-nitrocatecholic groups as NLO chromophores, which are components of the polymer backbone, was prepared. Polyurethane 5 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280°C from thermogravimetric analysis with glass-transition temperature (Tg) obtained from differential scanning calorimetry near 93°C. The second harmonic generation (SHG) coefficient (d33) of a poled polymer film at the 1064 nm fundamental wavelength is around 6.58 × 10−9 esu. The dipole alignment exhibits a thermal stability even at 7°C higher than Tg, and no SHG decay was observed below 100°C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.