NETWORKS FROM LIQUID-CRYSTALLINE SEGMENTED CHAIN POLYMERS

The synthesis and the phase behavior of three liquid crystalline polym er networks and of the linear polymers upon which the networks are bas ed are presented. The linear polymers, that are characterized by the p resence of -OC6H4-p-COOC6H3-o-OH-p-CH=NC6H4-p-O- groups connected by f lexible molecular segments, exhibit enantiotropic liquid crystalline p roperties of nematic and/or smectic nature. They have been moderately (less-than-or-equal-to 10%) cross-linked by reaction With ClOCC6H4-p-O (CH2)12O-p-C6H4COCl in an isotropic o-dichlorobenzene dilute solution. The networks form as isotropic gels and undergo anisotropization with enthalpy release on cooling at room temperature. No crystallization t akes place. Isotropization, accompanied by a DSC detectable endothermi c effect, is restored on heating. The neat networks exhibit also mesog enic properties, but the stability of their liquid crystalline phase i s decreased with respect to that of the corresponding linear polymers.