Worm-like micelles of triblock copolymer of ethylene oxide and styrene oxide characterised using light scattering and Taylor dispersion analysis

Abstract

A triblock ESE copolymer (E16S8E16, S = styrene oxide and E = ethylene oxide) was synthesised by sequential oxyanionic copolymerisation of styrene oxide followed by ethylene oxide. Light scattering studies demonstrated a shape transition from spherical micelles to worm-like micelles above a critical temperature of approximately 18oC. Taylor dispersion analysis (TDA) also indicated a size growth when the temperature increased from 25 to 40 oC due to the formation of worm-like micelles. The hydrodynamic radii and diffusion coefficients obtained by these two techniques were in good agreement. The solubility of a hydrophobic drug, terfenadine, in dilute micellar solutions of the copolymer was increased at least 20-fold under the conditions. The transition to worm-like micelles at raised temperatures led to enhanced solubilisation capacities due to a larger hydrophobic core volume. The behaviour of the novel ESE copolymer shows the utility of TDA to follow conformational changes using nanolitre quantities and explore critical quality attributes for this type of drug delivery system.