Synthesis and characterization of polyoxetanes containing 4-cyanobiphenyl-based side groups for nonlinear optical applications .1. Chemical modification of poly[3,3-bis(chloromethyl)oxetane] with sodium 4-cyano-4'-biphenyl oxide

Two copolyethers were prepared by chemical modification of poly[3,3-bis(chloromethyl)oxetane] with sodium 4-cyano-4'-biphenyl oxide, employing the concept of having the cyanobiphenyl species serve concomitantly as both the nonlinear optical chromophore and the mesogenic moiety in the polymer. Their thermal behavior was established by means of DSC and optical microscopy. Some preliminary Corona poling experiments were performed, and the second harmonic generation coefficients d(31) and d(33) were measured by Maker fringe analysis. The results showed that liquid crystallinity enhances field-induced polar ordering. The ratio d(33)/d(31) was found to be much larger than 3, in agreement with the theoretical models for electric field poling of liquid crystalline polymers where hyperpolarizable chromophores are attached as side groups to a polymer backbone.