A series of poly[ethylene-co-bis(2-ethoxy)hydroquinone terephthalate], PET-co-BEHQ copolymers were prepared by polymerization of various substituted bis(2-hydroxyethyl)hydroquinones (BEHQs), dimethyl terephthalate (DMT), and ethylene glycol (EG). In addition to copolymers containing 6 -16.5 mol % BEHQ, the homopolymer of BEHQ with dimethyl terephthalate, p(BEHQ-T), was also prepared. The thermal and barrier properties of amorphous materials were studied. As the amount of comonomer was increased, the T g and T m of the materials decreased relative to those of PET. Oxygen permeability also decreased with increasing comonomer content. This improvement in barrier-to-oxygen permeability was primarily due to a decrease in solubility of oxygen in the polymer. All of the copolymers tested displayed similar oxygen diffusion coefficients. The decrease in solubility correlates with the decrease in T g .

A one-pot preparation of 2,5-dihydrothiophene-1,1-dioxide-3carboxylic acid (3-sulfolene-3-carboxylic acid) is reported. The carboxylation of 3-sulfolene, exclusively at the 3-position, using CO 2 and DBU proceeds to >90% conversion. A rapid workup gives 3-sulfolene-3-carboxylic acid, a stable precursor to 1,3-butadiene-2-carboxylic acid. High conversions to Diels-Alder adducts were obtained upon treatment of 3-sulfolene-3-carboxylic acid with various dienophiles.

Summary: The successful incorporation of hydroquinone in thermal polyesterifications to prepare rigid linear copolyesters is hindered by the leaving group ability of phenols in nucleophilic acyl substitution reactions, the low nucleophilicity of phenols relative to aliphatic alcohols, and its volatility. To overcome these obstacles, with particular regard to improving the properties of poly(ethylene terephthalate), PET, we chose an approach whereby dyad‐based AB‐type mono(acetoxyphenyl) terephthalate monomers are transesterified into PET. In contrast to attempts to copolymerize terephthalic acid, ethylene glycol (EG) and hydroquinone, the transterification of small amounts (<10 mol‐%) of the preformed dyad in the absence of aliphatic diol, provides homogeneous random copolymers. Incorporation of larger amounts of aromatic diol gave only partly soluble materials. NMR analysis of the soluble fraction (in 20 vol.‐% TFA:CHCl3) indicated that the copolymers are substantially random. Transesterification of mono(4‐acetoxyphenyl) terephthalate (hydroquinone‐terephthalic acid, 1) and mono(3‐acetoxyphenyl) terephthalate (resorcinol‐terephthalic acid, 2) into PET allows us to further explore the effect of mesogen structure on the development of liquid crystalline copolyesters. magnified image

The One-Pot Synthesis and Diels-Alder Reactivity of 2,5-Dihydrothiophene--1,1-dioxide-3-carboxylic Acid. -The title compound (III), which is a stable precursor of 1,3-butandiene-2-carboxylic acid, is synthesized and its reactivity towards various dienophils is tested. -(ANDRADE, G. S.; BERKNER, J. E.; LIOTTA, C. L.; ECKERT, C.; SCHIRALDI, D. A.; ANDERSEN, A.; COLLARD*, D. M.; Synth.