SYNTHESIS OF NLO DIACRYLATE MONOMERS AND THEIR PHOTOCOPOLYMERIZATIONSWITH LC DIACRYLATE MONOMERS IN MIXED LIQUID-CRYSTALLINE STATE

The photocopolymerization (photocrosslinking) of mixed liquid crystals (LCs) consisting of LC diacrylate monomers and nonlinear optical (NLO ) diacrylate monomers exhibiting no liquid crystallinity under contact poling at optimum temperature was investigated to obtain a thermally stable NLO polymeric material. Novel NLO monomers, BAASA and BAOSA, as well as LC monomers, BAOOB3 and PAOB, were synthesized and the liquid crystallinity of their mixed LCs was investigated. The affinity of BA OSA with the LC monomers is generally better than that of BAASA. LC mi xtures prepared using BAOOB3 as LC matrix show only a smectic phase an d do not respond to poling though fixation of the mixture by photocros slinking occurs tightly. A PAOB matrix results in a nematic phase but not a smectic phase and the LC mixture responds not only to poling but also to photocopolymerization in the nematic phase. The photocrosslin king reaction of a BAOSA/PAOB (mole ratio 1/9) mixture under poling at 129 degrees C (nematic phase) proceeds effectively and gives a therma lly stable polymer film with a chi(33)((2)) value of 1.2-1.7 x 10(-8) esu(a), while the polymer film formed by photocrosslinking at 140 degr ees C (isotropic phase) shows a one order lower chi(33)((2)) value (3- 5 x 10(-9) esu).