Synthesis and characterization of second-order nonlinear optical polyurethane with high thermal stability

A second-order nonlinear optical polyurethane was formed with an X-type mufti-dimensional charge-transfer (CT) chromophore (DNPIPDHPI) and 3,3'-dimethoxy-4,4'-diphenyl diisocyanate. Simultaneous poling and polymerization and in situ second harmonic generation (SHG) measurement technique was carried on to evaluate the thermal stability of the poling induced orientation. The SHG signal of the poled polymer film was not decay below 150 degreesC and remains 90% of relative d(33) value at 200 degreesC, which is better than the results reported in literature. Comparison of thermal stability indicates that the X-type chromophores possess better property in controlling the decay of the SHG activity than classic chromophores. (C) 2004 Elsevier Ltd. All rights reserved.