LIQUID-CRYSTALLINE POLY(ESTER AMIDE)S BASED ON N,N-DIMETHYLDIAMINES AND AN AROMATIC ESTER TRIAD

A series of thermotropic liquid crystalline poly(ester amide)s was syn thesized based on various N,N'-dimethylalkylenediamines and terephthal oyl bis(4-oxybenzoyl chloride), TBOC. Several different synthetic proc edures were investigated to synthesize liquid crystalline (LC) polymer s having a broad range of molecular weights. The highest molecular wei ght polymers were obtained by the low-temperature solution condensatio n of N,N'-bis(trimethylsilyl)diamines and TBOC. Analyses of the polyme rs by wide angle X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy showed that the as-prepared crystal line polymers melted to form a nematic, liquid crystalline phase, whic h showed no evidence of recrystallization upon cooling. The LC polyest eramides with a B-methylene spacer unit exhibited a monotropic behavio r in contrast to the polymers or copolymers with a 12-methylene spacer unit which are enantiotropic. Changes in polymer conformation which o ccurred on heating in the solid state and in the liquid crystalline st ate were evaluated by solid state C-13 cross polarization magic angle spinning NMR spectroscopy which showed that the polymers had considera ble mobility at temperatures well below the crystalline melting point. The polymers, when precipitated from solution, contained mixtures of syn and anti amide units, but after melting, the syn amide unit was ex clusively obtained indicating that it is likely the most thermodynamic ally stable conformation.