Amorphous copolyesters based on bibenzoic acids and neopentyl glycol

High T-g amorphous copolyester thermoplastics were synthesized by incorporating 4,4 '-bibenzoate (4,4 ' BB) and 3,4 '-bibenzoate moieties into the polyester backbone via melt polycondensation. The high levels of crystallinity typically associated with 4,4 ' BB containing polyesters were suppressed through copolymerization of ethylene glycol, 1,4-cyclohexane dimethanol, and neopentyl glycol (NPG) diols. NPG was shown to be highly effective in suppressing crystallization and was used to produce amorphous compositions with T-g's as high as 129 degrees C. Diol ratios were determined by H-1 NMR spectroscopy and molecular weights were assessed with inherent viscosity (eta(inh)). Thermogravimetric analysis showed single-step weight losses in the range of 395-419 degrees C. Differential scanning calorimetry was used to determine melting points and glass transition temperatures over a wide range of copolyester compositions and identified amorphous compositions. Dynamic mechanical analysis confirmed T-g's and was used to study beta-relaxations below the T-g. Rheological analysis revealed the effect of NPG structures on shear thinning and thermal stability. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 579-587