Using 4,4'-diphenylmethane diisocyanate (MDI) and p-diamino nitro benzene (DNB), polyurea (PU(DNB)) films were fabricated by vapor deposition polymerization for second-order nonlinear optical application. In PU(DNB), although the enhanced optical nonlinearity due to the introduction of the NO/sub 2/ group was achieved, a drastic decay of SH intensity was observed at 200/spl deg/C. The structural analysis revealed that the polymerization proceeded during the heat treatment but not during the poling process. This is attributed to the hindrance to the polymerization due to the reduction of reactivity of the NH/sub 2/ group under the poling field.
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机译：使用4,4'-二苯基甲烷二异氰酸酯（MDI）和对二氨基硝基苯（DNB），通过气相沉积聚合制备聚脲（PU（DNB））膜，用于二阶非线性光学应用。在PU（DNB）中，尽管由于引入了NO / sub 2 /基团而获得了增强的光学非线性，但是在200 / spl deg / C下观察到了SH强度的急剧衰减。结构分析表明，聚合反应在热处理过程中进行，但在极化过程中没有进行。这归因于在极化场下由于NH / sub 2 /基团的反应性降低而导致的聚合阻碍。
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