Lyotropic liquid crystalline polyesters: synthesis of polyesters and copolyesters based on poly(sulfo-p-phenylene nitroterephthalate)

Abstract

The syntheses of the polyesters poly(sulfo-p-phenylene methoxyterephthalate) (4), poly(sulfo-p-phenylene 2-methoxy-5-nitroterephthalate) (5) and poly(sulfo-p-phenylene 2-bromo-5-nitroterephthalate) (6), and the random copolyesters poly([sulfo-p-phenylene nitroterephthalate]_x-co-[sulfo-p-phenylene terephthalate]) (7a–c), poly([sulfo-p-phenylene nitroterephthalate]_y-co-[sulfo-p-phenylene bromoterephthalate]) (8a–c) and poly([sulfo-p-phenylene nitroterephthalate]_z-co-[sulfo-p-phenylene nitro-isophthalate]) (9a–f) are reported. It was found that, of the three new homopolyesters prepared, 5 showed lyotropic behaviour in 1:1 DMSO–H₂O, DMSO and DMF (DMSO=dimethyl sulfoxide; DMF=dimethylformamide). The copolymers were prepared in various monomer compositions in an effort to establish the effect of either (a) diluting the mesogenic character of a known liquid crystalline polyester by reducing the nitro ratio of the substituents, or (b) disrupting the main-chain linearity of the ester back-bone by the introduction of meta-arranged isophthalate units. It was found that the original polyester could incorporate up to 50% bromo- or un-substituted terephthalate units and retain the ability to form lyotropic solutions. In the case of the accommodation of nitroisophthalate units, only 9% could be tolerated. Poly(sulfo-p-phenylene nitroterephthalamide) (10) has also been synthesised and shown to form a lyotropic liquid crystalline phase in DMSO and aqueous DMSO.