SYNTHESIS AND CHARACTERIZATION OF BRANCHED LIQUID-CRYSTALLINE POLYETHERS CONTAINING CYCLOTETRAVERATRYLENE-BASED DISK-LIKE MESOGENS

The synthesis and characterization of branched liquid-crystalline polyethers containing disk-like mesogens are described. The particular disklike molecules employed for these experiments are octaalkyloxy-substituted cyclotetraveratrylene derivatives (CTTV-n). The model compounds of the monomeric structural units (i.e., asymmetrically disubstituted [CTTV-n[m(x/y)]) were synthesized by the electrophilic cocyclotetramerization of 3,4-bis(n-alkyloxy)benzyl alcohols [1(n)], while the branched polymers were synthesized by the cocyclotetramerization of various ratios of a mixture containing 3,4-(di-n-alkyloxy)benzyl alcohol and alpha,omega-bis[[2-(n-alkyloxy)-5-(hydroxymethyl)phenyl]oxy]alkane [2(n,m)]. CF3COOH was used as the cyclotetramerization catalyst. This novel polymerization reaction constructs the disklike CTTV-n molecules during the polymerization process. In a columnar mesophase the backbone of a main-chain liquid-crystalline polymer containing disklike mesogens can either connect mesogens from adjacent columns (intercolumnar bridging) or link two mesogens within the same column (intracolumnar backfolding). Therefore, since such a polymer resembles a rigid networklike structure, we believe that the branched structure described in this publication represents a rational architecture for polymers containing disklike mesogens. Preliminary data on the characterization of the mesomorphic behavior of model compounds of the monomeric structural units, of a twin discotic dimer, and of the branched oligomers, obtained by a combination of differential scanning calorimetry and thermal polarized optical microscopy, have shown that all exhibit discotic mesophases.