The synthesis of polyesters with a biphenyl skeleton by palladium catalyzed carbonylation-polycondensation

Abstract

For synthesizing heat-resistant polyesters, the one step synthesis of biphenyl-containing polyesters was developed from palladium-catalyzed carbonylation-polycondensation of dihalobiphenyls and bisphenols. Reaction parameters, such as base, solvent, palladium-phosphine catalyst and CO pressure in the reaction of 2,7-dibromo-9,10-dihydrophenanthrene and 4,4′-(1-methylethylidene)bisphenol (bisphenol A), were found to affect the molecular weight of poly[oxy-1,4-phenylene(1-methyethylidene)-1,4-pheny-eneoxycarbonyl-(9,10-dihydro-2,7-phenanthrenediyl)carbonyl] (2). The solution after the reaction was homogeneous when high molecular weight polyester was formed. The use of strong base such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) yielded high molecular weight polyesters. Key step for the reaction is considered the alcoholysis step. High nucleophilicity of phenoxide anion formed from the phenol moiety and DBU enhanced the step to increase the rate of the carbonylation-polycondensation. The use of palladium catalyst with PPh 3 gave higher molecular weight polyester than that with Ph 2P(CH 2) 3PPh 2 in spite of higher catalytic activity of the latter catalyst. This is due to higher termination rate caused by the carbonylation of chlorobenzene for the latter catalyst. Under optimum conditions, polyester 2 was obtained in 95% yield with high molecular weight (polystyrene equivalent M W = 102 600). Bisphenols with sufficiently bulkyalkyl spacers, such as 4,4′-cyclohexylidenebisphenol, 4,4′-(s-butylidene)bisphenol, 4,4′-(1-phenylethyl-idene) bisphenol, 4,4′-ethylidenebisphenol, 4,4′-methylidenebis(2,6-dimethylphenol) and 4,4′-(1-methylethylidene)bis(2,6-dimethylphenol) gave polyesters with high to moderately high molecular weight. On the basis of a thermal analysis, 5% weight loss temperature ( T 5) and 10% weight loss temperature ( T 10) of 2 in air was 394 and 414°C, respectively.