PHOTO-CROSS-LINKING OF A POLYURETHANE WITH PENDANT METHACRYLOYL-TERMINATED 4-ALKOXY-4'-SULFAMOYLSTILBENE NLO CHROMOPHORES

The photo-cross-linking of a polyurethane with pendant-oriented NLO chromophores terminated with methacryloyl groups has been achieved using free-radical photoinitiators. Due to the presence of trans-stilbene groups in the chromophore, the photo-cross-linking step must be restricted to the methacryloyl double bonds, proceeding without concurrent trans-cis isomerization of the stilbene. This can be achieved using an organometallic photoiniator that absorbs at 532 nm. Due to the high temperature used to achieve poling of the NLO chromophores, addition of a hindered phenol is necessary to prevent the onset of thermal crosslinking. Imagewise photo-cross-linking of the oriented polymer can be used to produce a patterned material that exhibits a stable second-order NLO signal for several weeks at 100-degrees-C.