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

Abstract

A new associating system has been elaborated from mixing a degradable polymer, poly(β-malic acid-co-β-ethyladamantyl malate), and a β-cyclodextrin 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 percentages of hydrophobic groups (0-7.5%) show that a small proportion of the chains (less than 5% in weight) are aggregated in large structures (100nm) which dominate the scattering intensity. The mixtures exhibit slow diffusive relaxation modes which correlate with a large viscosity enhancement at low concentration. These effects, which depend sensitively on pH, are attributed to the presence of polydisperse complexes of copolyester and β-cyclodextrin 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 amphiphilic copolyester.