THERMOTROPIC HYPERBRANCHED POLYESTERS PREPARED FROM 2-[(10-(4-HYDROXYPHENOXY)DECYL)OXY]TEREPHTHALIC ACID AND ROXY-1,1'-BIPHENYL-4-YL)OXY)DECYL)OXY]TEREPHTHALIC ACID

Two new thermotropic, liquid crystalline (LC) hyperbranched polyesters with carboxylic acid end groups were synthesized by direct polyconden sation of two pseudo AB(2) type monomers, 2-[(10-(4-hydroxyphenoxy)dec yl)oxy]terephthalic acid and xy-1,1'-biphenyl-4-yl)oxy)decyl)oxyl]-ter ephthalic acid. Their LC properties were characterized by DSC and opti cal microscopy. The carboxylic acid groups of the polyesters were conv erted to the corresponding methyl esters, and their properties were al so investigated. The number average molar masses of the polymers were 7000 and 15 000, respectively, corresponding to average degrees of pol ymerization of about 17 and 31. The degrees of branching of the polyme rs determined by C-13 NMR spectroscopy were 37 +/- 10% and 43 +/- 10%, respectively. The polyesters with the carboxylic acid end groups form the nematic phase above their glass transition temperatures (T-g), wh ereas their methyl ester counterparts are not liquid crystalline. This observation indicates that the formation of hydrogen bonds between th e carboxylic acid terminals plays an important role in mesophase forma tion by the present polyesters. All the polymers are amorphous and are soluble in common organic solvents such as THF, DMF, NMP, pyridine, a nd DMSO. The T-g values of the methyl ester polymers are substantially lower than those of the polymers having acid terminals.