Water-soluble polvmers and gels from the polycondensation between cyclodextrins and poly(carboxylic acid)s: A study of the preparation parameters

Native cyclodextrins (CDx) and some of their derivatives were reacted with poly(carboxylic acid)s (PCAs) [citric acid (CTR), 1,2,3,4-butanetetracarboxylic acid (BTCA), and poly(acrylic acid) (PAA)]. These reactions were carried out in the dry state at a temperature greater than 140 degrees C in air or in vacuo. They resulted in water-soluble and insoluble polymers formed by polyesterification between CDx and PCA. In this study, the parameters of the reaction were studied, and their influence on the water solubility or swellability of the obtained polymers was investigated. High reaction temperatures, high PCA/CDx molar ratios, and long reaction times preferably yielded insoluble gels, whereas softer conditions resulted in very soluble polymers. The gels could swell up to 10 times their initial volume in water, and the water-soluble fraction had a solubility of I g/mL. A reaction mechanism was proposed that required the use of PCA carrying at least three neighboring carboxylic groups (CTR, BTCA, and PAA), and it was confirmed experimentally by the unsuccessful use of some dicarboxylic acids. A preliminary characterization by Fourier transform infrared spectroscopy and size exclusion chromatography was also conducted. (c) 2005 Wiley Periodicals, Inc.