block-Copoly(oxyethylene/oxybutylene/oxyethylene), E40B15E40, in aqueous solution: micellisation, gelation and drug release

Abstract

Triblock copoly(oxyethylene/oxybutylene/oxyethylene) E₄₀B₁₅E₄₀ was prepared by sequential anionic copolymerisation and its micellar, gelation and drug release properties in aqueous solution were investigated. The gel region of the temperature–concentration diagram was identified, including the lower and upper temperature gel–sol boundaries. Static and dynamic light scattering measurements were made on solutions at 20.5–22.5, 37 and 65 °C over a wide concentration range from dilute solution into the gel range (>230 g kg^–1) and at high concentration, including the gel phase, over the temperature range from 20.5 to 70 °C. A brief investigation of the rate of release of salicyclic acid from the gel served to illustrate useful sustained release. The gelation behaviour, interpreted via the hard-sphere model, was consistent with the measured micellar sizes.