Synthesis, thermal and radiation sensitivities of fluorine containing methylene-bridged aromatic polyesters

A series of fluorine-containing, methylene-bridged aromatic polyesters were synthesized by interfacial polymerization from 4,4'-oxybis(benzoic acid) or 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) with bisphenol A or hexafluorobisphenol A. The effect of the fluorine substituent on the structure and properties of the polyesters was investigated by systematically varying the position and content of the fluorine substitution. Incorporation of perfluoroisopropylidene groups in the polymer backbone enhanced the solubility of the polyesters in various organic solvents, and all of these polyesters were soluble in m-cresol as well as chloroform and tetrahydrofuran. The inherent viscosities of these solutions ranged from 0.15 to 0.82 dl g(-1), depending on the polyester structure. The structures of the polyesters were confirmed by means of i.r. spectroscopy, H-1 and C-13 n.m.r. spectroscopies and elemental analyses. The polyesters were shown to be amorphous by X-ray diffraction measurements. The glass transition temperatures, thermal stabilities, and radiation sensitivities of the polymers have been investigated. The temperatures for a 5% weight loss during thermal degradation of the polymers containing the oxy-bis(benzoic acid) units were approximately 100-140 degrees C higher than those containing the hexafluoroisopropylidene-bis(benzoic acid) units, but fluorine substitution in the bisphenol A units had only a small effect on this degradation temperature. There was little difference between the sensitivities of the polymers to high energy radiation degradation, with the G-values for radical formation at 77K for all of the polymers lying in the range 0.38-0.46, but here fluorine substitution tended to enhance polymer stability. (C) 1997 Elsevier Science Ltd.