The fluorescence measurements of tetraethylene glycol dodecyl ether (C12E4) and triblock-polymer (Pluronic P103), poly(ethylene oxide)poly(propylene oxide)-poly(ethylene oxide), (EO)17(PO)(60)(EO)(17), binary mixtures have been performed over the whole mixing range in the temperature range of 20-40 degrees C. The results have been evaluated by computing various micellar parameters and excimer formation. It has been concluded that mixed micelle formation takes place due to unfavorable mixing at lower temperature ran-e, and the magnitude of which decreases with the increase in temperature up to 40 degrees C. The reduction in the unfavorable mixing has been attributed to the dehydration of P103 micelles with the increase in temperature. (c) 2005 Elsevier Inc. All rights reserved.