SYNTHESIS AND CHARACTERIZATION OF POLYOXETANES CONTAINING 4-CYANOBIPHENYL-BASED SIDE-GROUPS FOR NONLINEAR-OPTICAL APPLICATIONS .2. SYNTHESIS, CHARACTERIZATION AND POLYMERIZATION OF 3,3-BIS(4-CYANO-4'-BIPHENYLYLOXYMETHYL) OXETANE

3,3-Bis(4-cyano-4'-biphenylyloxymethyl)oxetane was prepared by reactio n of 3,3-bis(chloromethyl)oxetane with the sodium salt of 4-cyano-4'-h ydroxybiphenyl. With highly purified dichloromethane, single crystals could be prepared. The X-ray patterns could be indexed in terms of a m onoclinic cell a = 13,87 Angstrom, b = 14,74 Angstrom, c = 13,91 Angst rom and beta = 118,68 degrees. Some experiments were carried out to de termine the cationic polymerization behavior of this oxetane. The init iating system BF3 . Et(2)O/dichloromethane was used and it was shown t hat unusually high initiator concentrations were necessary to observe polymerization. By means of steric exclusion chromatography and NMR sp ectroscopy, the formation of cyclic oligomers was evidenced. Upon heat ing, all the polymers showed a nematic phase. Some preliminary Corona poling experiments were performed and the second harmonic generation c oefficients d(31) and d(33) were measured. It was shown that one can g ain in net polar ordering by starting with a liquid crystalline system . The ratio d(33)/d(31) was found to be much larger than 3 in agreemen t with the molecular statistical models for electric field poling of l iquid crystals.