Solubilisation of polyaromatic hydrocarbons in aqueous solutions of poloxamine T803

Abstract

The solubilisation of exemplar polyaromatic hydrocarbons (PAHs) in aqueous solutions of the block co-polymeric surfactant T803 has been investigated. The PAHs used were naphthalene, phenanthrene and pyrene. T803 is a tetrafunctional block co-polymer derived by way of the coupling of ethylene oxide and propylene oxide to ethylene diamine. The presence of the ethylene diamine moiety provides the compound with pH functionality. In particular, micellisation in these systems is shown to be pH dependent. As a consequence, solubilisation in T803 solutions is also shown herein to be pH dependent, giving rise to considerable changes in the apparent aqueous solubilities of the PAHs. A switch in pH from 4 to 10.3 changes the apparent aqueous solubility of naphthalene, phenanthrene and pyrene by one, two and three orders of magnitude, respectively. Likewise, changes in temperature from 25 to 40 °C also produce changes of similar orders of magnitude in the apparent aqueous solubilities of phenanthrene and pyrene at a pH of 5.6 and T803 concentration of 5 mM.