Synthesis of symmetric and asymmetric carbazolyl monomers and their siloxane polymers. Effect of the 2,3,6,7,9-substitution in the carbazole unit on its mesomorphic behaviour

A general synthetic route toward symmetric and asymmetric side-on and end-on carbazolyl monomers has been developed. The effect of the nature of the core on the induction of liquid-crystal phases in side-on carbazolyl polysiloxanes has been studied. Chromophores have been introduced into the carbazole core to produce materials with improved second-order non-linear optical (NLO) properties. The mesomorphic behaviour of all the polymers has been investigated by optical microscopy, differential scanning calorimetry (DSC) and X-ray diffraction. The side-on polymers are isotropic or crystalline except one of them that presents a metastable nematic phase.