Synthesis and characterization of novel heterocyclic-ring-based poly(arylene ether)s

Heterocyclic-ring-based poly(arylene ether)s (PAEs) are considered to be a unique class of high-temperature polymers which find use as structural resins for a variety of aerospace applications. Incorporation of heterocyclic units in the backbones of PAEs offers certain advantages over PAEs without heterocyclic units such as higher glass transition temperature (T-g), tensile strength and modulus. Heterocycles such as phenylquinoxalines, benzoxazoles, benzothiazoles, oxadiazoles, triazoles, imidazoles and benzin-tidazoles, etc., have been incorporated into the backbones of PAEs via the aromatic nucleophilic displacement reaction. The resulting polymers showed excellent thermal properties. In view of the excellent thermal properties of heterocyclic ring based poly(arylene ether)s, some novel heterocyclic ring structures, such as thioxopyrimidinedione, amidotriazine, amidothiazole, imidothiazole and thiadiazine, have been successfully introduced into the backbones of poly(arylene ether)s. It was observed that the T-g of synthesized polymers was in the range 150-197 degrees C and most of the polymers showed no weight loss below 400 degrees C. The focus of this paper is, therefore, on structure-property relationships between the variety of heterocyclic rings introduced into the polymeric backbone and their effect on thermal properties of the resulting polymers.