BLOCK-COPOLY(OXYETHYLENE OXYBUTYLENE OXYETHYLENE), E40B15E40, IN AQUEOUS-SOLUTION - MICELLIZATION, GELATION AND DRUG RELEASE

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-degrees-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-degrees-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.