pH Sensitive supramolecular assembling system between a new linear water soluble β-cyclodextrin terpolymer and an amphiphilic poly(ethylene oxide)

A linear water soluble beta-cyclodextrin terpolymer (P(MVE-AM)-g-beta CD) was synthesized by grafting different amounts of beta CD on the copolymer P(MVE-AM). The resulting terpolymer showed a pH sensitive behaviour in aqueous solution, due to the presence of carboxylic acid groups. Whatever the substitution degree in beta CD, the terpolymer behaved like a polyacid at pH 7, and had neutral properties at pH 2. The mixture of P(MVE-AM)-g-beta CD with an amphiphilic poly(ethylene oxide) (PEO-Ad(3)) showed an associative phase separation influenced by the pH and concentration of the medium. In the dilute range and intermediate range, associative phase separations were induced reversibly by decreasing the pH from 7 to 2. The results in the semi-dilute range showed that networks were elaborated with much stronger dynamic modulus at low pH (pH 2) than at higher pH (pH 7). Coupled inclusion complex interactions (between the adamantyl groups of PEO-Ad(3) and the cyclodextrin cavities of P(MVE-AM)-g-beta CD) with hydrogen bonding (between carboxylic acid groups and PEO backbone) could be a way to modulate the strength of the interactions in supramolecular assemblies. These results suggest that the mixture of P(MVE-AM)-g-beta CD with PEO-Ad(3) could be a potential pH sensitive system. (C) 2008 Elsevier Ltd. All rights reserved.