Association between amphiphilic poly(ethylene oxide) and β-cyclodextrin polymers: aggregation and phase separation

An original associating system is presented in this paper. It involves the mixing of two polymers: hydrophobically modified polyethylene oxide (PEO) and β-cyclodextrin copolymer. Inclusion complexes between the hydrophobic moieties (naphthalene or adamantane) and β-cyclodextrin cavities are at the origin of the attraction between the two polymers. The strength of the attractive interactions has been tailored by using different architectures for the amphiphilic polymer: linear or multi-arm branched PEO have been used, leading to a variable number of hydrophobic end-groups per chain. Interactions between the host and guest polymer have been demonstrated through both microscopic and macroscopic analysis of the properties of the medium: complexation constants have been determined by fluorescence methods and dialysis, while polymolecular associations have been evidenced by viscoelastic properties. Phase diagram studies have shown that the strength of the interactions between the two polymers is strongly related to the number of hydrophobic moieties per chain: while unmodified PEO and β-cyclodextrin copolymer are phase segregating, associative phase separations are observed for a number of hydrophobes per chain higher than or equal to three.