ABSTRACT Pluronics F127 or (PEG)99–(PPG)69–(PEG)99 (with PEG and PPG representing polyethylene glycol and polypropylene glycol, respectively) was chemically modified by reacting with poly(polytetrahydrofuran carbonate) (PTHF) diol using a standard poly(urethane) reaction. The poly(F127/PTHF urethane)s showed lower critical gelation concentration as compared with Pluronics F127. The solution properties of these polymers were investigated at different temperatures using a hydrophobic dye probe. The thermodynamic variables associated with micelle formation were determined. This study uncovered valuable structure–property relationships affecting the micellization and gelation behavior. We tested these materials as potential ophthalmic delivery agents for the sustained release of natamycin for the treatment of eye infections. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39924.