Micellization of block copolymer P94 in aqueous solution

P94 is a triblock copolymer of poly(oxyethylene) and poly(oxypropylene), type EPE. Eluent gel permeation chromatography has been used to demonstrate the formation of large micelles in solutions of the copolymer at temperatures immediately above the critical micelle temperature. Values of the critical micelle temperature (cmt) obtained in this way are in excellent agreement with results from differential scanning calorimetry and surface tensiometry. A van't Hoff plot was used to define the concentration dependence of the cmt for dilute solutions (c < or =2 wt%) and to obtain an apparent value of the standard enthalpy of micellization. Using published data, comparison is made with the thermodynamics of micellization in concentrated solution (c > or =20 wt%).