NETWORKS FROM LIQUID-CRYSTALLINE SEGMENTED CHAIN POLYMERS

The synthesis and the phase behavior of three liquid crystalline polymer networks and of the linear polymers upon which the networks are based are presented. The linear polymers, that are characterized by the presence of -OC6H4-p-COOC6H3-o-OH-p-CH=NC6H4-p-O- groups connected by flexible molecular segments, exhibit enantiotropic liquid crystalline properties 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 takes place. Isotropization, accompanied by a DSC detectable endothermic effect, is restored on heating. The neat networks exhibit also mesogenic properties, but the stability of their liquid crystalline phase is decreased with respect to that of the corresponding linear polymers.