Investigations of Naphthalene Solubilization in Aqueous Solutions of Ethylene Oxide-b-Propylene Oxide-b-Ethylene Oxide Copolymers

Abstract

The enhanced apparent solubility of naphthalene in aqueous solutions of several ABA block copolymeric surfactants has been measured using HPLC. The surfactants investigated combine, within their structure, a block of propylene oxide (PO) (the hydrophobic B block) sandwiched between two blocks of ethylene oxide (EO) (the hydrophilic A blocks). This commercially produced family of surfactants encompass a variety of materials which differ from each other in terms of block sizes and thus in terms of the balance of hydrophobic and hydrophilic forces. It is this balance which controls the ability of the surfactants to effect particular solubility enhancements. Substantial increases in solubility arise from the incorporation of naphthalene into block copolymer micelles. However the experimental data also point to solubility enhancements arising from naphthalene−surfactant interactions at surfactant concentrations below the critical micelle concentration (cmc). The apparent equilibrium constantdescribing the solu...