Associations between a hydrophobically modified, degradable, poly(malic acid) and a beta-cyclodextrin polymer in solution

A new associating system has been elaborated from mixing a degradable polym er,poly(beta -malic acid-co-beta -ethyladamantyl malate), and a beta -cyclo dextrin polymer in aqueous solution. Viscosity and dynamic light scattering measurements have been made on solutions of the single copolyester and of mixtures of both polymers. Studies on copolyesters with different percentag es of hydrophobic groups (0-7.5%) show that a small proportion of the chain s (less than 5% in weight) are aggregated in large structures (100 nm) whic h dominate the scattering intensity. The mixtures exhibit slow diffusive re laxation modes which correlate with a large viscosity enhancement at low co ncentration. These effects, which depend sensitively on pH, are attributed to the presence of polydisperse complexes of copolyester and beta -cyclodex trin polymer. The influence of pH, ionic strength, medium composition, and concentration were examined on the mixture of copolymers. It was found that the association properties are controlled by the net charge on the amphiph ilic copolyester. (C) 2001 Society of Chemical Industry.