SYNTHESIS AND CHARACERIZATION OF A SERIES OF MESOGEN-JACKETED LIQUID CRYATALLINE POLYMERS WITH LONG MESOGENIC SIDE CHAINS

Abstract

A series of mesogen-jacketed liquid crystalline polymers,poly[2,5-(4′-alkoxybi-phenyloxycarbonyl) styrene](PnCbiPCS,n=4,6,8,10,14) with long mesogenic side chains,were prepared by atom transfer radical polymerization(ATRP).Molecular weights and molecular weight distributions of the polymers were measured by gel permeation chromatography(GPC).The liquid crystalline(LC) behavior was studied by a combination of differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),polarized light microscopy(PLM),one-dimensional(1D) and two-dimensional(2D) wide-angle X-ray diffraction(WAXD),and small-angle X-ray scattering(SAXS).All the polymers had good thermal stablility and exhibited stable LC properties,and no isotropization temperatures were observed before the onset temperatures of thermal decomposition.1D SAXS and WAXD studies revealed that PnCbiPCS could form smectic structures with the long mesogenic side chains aligned parallel to each other.The d-spacings increased with increasing aliphatic tails.2D WAXD results showed that the sheared samples exhibited Smectic A structures with the layer normal perpendicular to the shear direction.Comparing with the results of poly{2,5-bis[(para-substituted phenyl)oxycarbonyl]styrene}s,one may indicate that the length of the mesogenic group is crucial in determining the LC structure.