Association between amphiphilic poly(ethylene oxide) and beta-cyclodextrinpolymers: 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) a nd beta-cyclodextrin copolymer. Inclusion complexes between the hydrophobic moieties (naphthalene or adamantane) and beta-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 us ed, leading to a variable number of hydrophobic end-groups per chain. Inter actions between the host and guest polymer have been demonstrated through b oth microscopic and macroscopic analysis of the properties of the medium: c omplexation constants have been determined by fluorescence methods and dial ysis, while polymolecular associations have been evidenced by viscoelastic properties. Phase diagram studies have shown that the strength of the inter actions between the two polymers is strongly related to the number of hydro phobic moieties per chain: while unmodified PEO and beta-cyclodextrin copol ymer are phase segregating, associative phase separations are observed for a number of hydrophobes per chain higher than or equal to three. (C) 1999 E lsevier Science B.V. All tights reserved.