PHASE-BEHAVIOR OF A NETWORK POLYMER BASED ON A SEGMENTED-CHAIN POLYMERIC MESOGEN

The phase behavior of a polymer network obtained by moderately cross-linking a segmented-chain liquid crystalline polymer is presented. The network was formed by reacting H2NC6H4-P-O(CH2)6O-p-C6H4NH2 with an o-dichlorobenzene solution of a polyester previously prepared by reaction of 2,5-dihydroxybenzaldehyde with ClOCC6H4-p-O(CH2)10O-P-C6H4COCl. The network shows thermotropic nematic behavior of a cybotactic type as observed for the linear polymer. However, the mesophase stability is significantly reduced. The origin of this reduction is discussed and related to the intrinsic decrease of the mesogenic potential of the linear chains forming the network. The phase behavior of the swollen network is also examined. The formation of a noncrystalline anisotropic gel at temperatures lower than approximately 80-degrees-C is observed with a polymer/solvent ratio ranging between 0.065 and 0.080. Isotropization takes place on heating and is accompanied by an enthalpic increase. The H-1-NMR spectrum of the anisotropic gel suggests that the gel has a biphasic structure rather than a lyotropic single structure.