Effects of Polypropylene Glycol 400 (PPG400) on the Micellization and Gelation of Pluronic F127

In dilute aqueous solution unimers of Pluronic F127 associate to form micelles. In more concentrated solution, micelles pack to form high-modulus gels. Our interest is the effect of addition of 10-30 wt % low molecular weight PPG400 on the micellization and gelation of solutions of F127. DLS was used to determine the apparent size of the micelles (r(h,app)). The critical micelle concentration (cmc) using the dye solubilization method of F127 in PPG400 solutions was studied. Visual observation was carried out to detect gel formation in concentrated solutions and the onset of clouding and turbidity, as the temperature was raised. Oscillatory rheometry was used to confirm the formation of high-modulus gels and provide values of elastic moduli (G(max)') over a wide temperature range. SAXS was used to determine gel structure. Our results for the hydrophobic adduct PPG400 were compared with literature values for the hydrophilic adduct PEG6000.