LIQUID-CRYSTALLINE POLYETHERS BASED ON CONFORMATIONAL ISOMERISM .23. SYNTHESIS AND CHARACTERIZATION OF A THERMOTROPIC NEMATIC LIQUID-CRYSTALLINE DENDRIMERIC POLYMER

The synthesis and characterization of 1-(4-hydroxy-4'-biphenylyl)-2-(4-hydroxyphenyl)decane (TPD) and of 10-bromo-1-(4-hydroxy-4'-biphenylyl)-2-(4-hydroxyphenyl)decane (TPD-b) are described. Polyetherification of TPD with alpha,omega-dibromoalkanes containing from 6 to 10 methylene units leads to the model polyethers TPD-X (where X = 6-10 and represents the number of methylene units in the flexible spacer). TPD-X with X = 6, 8, and 10 exhibit an enantiotropic nematic mesophase, while those with X = 7 and 9 are glassy. Homopolymerization of TPD-b followed by in situ alkylation of the phenol chain ends leads to the TPD-b-X dendrimeric polymers (X is the structure of the alkylated phenol chain ends, i.e., Bz = benzyl, 4 = butyl 6 = hexyl, 8 = octyl). TPD-b-X with X = Bz, 6, and 8 represent the first examples of dendrimeric polymers which exhibit a thermotropic enantiotropic nematic mesophase. The isotropization temperature of the TPD-b-X is lower than that of their linear model TPD-8.