STRUCTURAL STUDY OF THERMOTROPIC LIQUID-CRYSTALLINE POLY(ETHYLENEIMINIUM) SALTS ALKYLATED WITH MESOGENIC SIDE-CHAINS

Ionic liquid crystalline polymers were obtained from linear poly(ethyl eneimine) (PEI) substituted with 6-(4-methoxy-4'-biphenylyloxy)hexyl b romide or 12-(4-methoxy-4'-biphenylyloxy)dodecyl bromide, and quaterni sed with dimethyl sulfate or hydrobromic acid. Their thermotropic poly morphism was studied by means of differential scanning calorimetry (DS C), polarising optical microscopy and X-ray diffraction. A smectic A m esophase was identified and described from a structural point of view with the help of computer modelling. The completely alkylated and quat ernised PEI derivative was shown to form a single layered smectic A st ructure with pendant groups all on the same side of the polymer backbo ne in a double row ribbon-like configuration. The ribbon-like polymer chains are packed side by side with the polymer backbone parallel to t he smectic layers and the mesogenic groups perpendicular to them. For partially alkylated or quaternised PEI derivatives, the layer spacing in the smectic A mesophase is generally different from that of the cor responding molecular length calculated for fully functionalised polyme rs.