Poly(amide imide)s and poly(amide imide) composite membranes by interfacial polymerization

Abstract

Novel amic acid diamines (AADs) (2-carboxyterephthalamido-bis(alkyl or aryl amine)s, H2N-X-NH(O=)C-C6H3(COOH)-C(=O) NH-X-NH2, where X is (CH2)2, (CH2)3, CH2C6H10 CH2, N NCH2CH2, C6H4, C6H4OC6 H4 or C6H4CH2C6 H4 were synthesized by reacting trimellitic anhydride chloride with aromatic or aliphatic diamines in dimethylformamide at 5-10°C. Poly(amide imide)s (PAIs) with an amide to amide ratio of three in the polymer chains were prepared by interfacial polycondensation of the AADs in acqueous alkaline solution with isophthaloyl chloride or terephthaloyl chloride in dichloromethane at ambient temperature to form poly(amide amic acid)s, followed by their subsequent thermal cycloimidization. All of the PAIs were soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone, and have inherent viscosites in the range 0.15-0.48 dL g-1. The polymers were characterized by IR and NMR spectroscopy, TGA and DSC techniques. The PAIs have initial decomposition temperatures in the range of 250-450°C in air, and glass transition temperatures of 128-320°C, depending upon the structures of the monomers. Composite membranes containing a poly(amide amic acid) and poly(amide amide) barrier layer on the top of a porous polyethersulfone support were prepared by in situ interfacial polymerization of the AADs in aqueous alkaline solution with trimesoyl chloride in hexane, and subsequent curing. The performances of these membranes were evaluated by using aqueous feed solutions containing 2000 ppm NaCl, Na2SO4 or CaCl2. © 2006 Society of Chemical Industry.