Taylor-Aris Diffusion Studies of Solute-Polymer Interactions. 1. Alkyl p-Hydroxybenzoates with an ABA Block Copolymer (Poloxamer P407) in Aqueous Solution

This paper describes the application of the Taylor-Aris dispersion technique to the study of the diffusion of an homologous series of alkyl p-hydroxybenzoates in aqueous solutions of an ABA block copolymer, Poloxamer P407. The fraction of polymer incorporated solute was calculated after correction of the diffusion coefficients for polymer obstructional effects. These fractions increase along the homologous series allowing the use of a group contribution approach to evaluate the increment in the Gibbs function per methylene group for the incorporation process. The value obtained, -1.9 kJ mol(-1), reveals that the solubilization sites provided by the polymer aggregates are similar to those reported for micelles of low molar mass surfactants. The nature of the possible interactions between these solutes and the polymer micelles is also discussed.