A series of environmental pH-responsive block copolymers PEG-polyurethane with tertiary amine groups in the main chain and free carboxyl groups in the side chain were synthesized, including poly(ethylene glycol) (PEG), 1,4-bis (hydroxyethyl) piperazine, 1,6-diisocyanato hexamethylene, and 2,2-dimethylolpropionic acid. The chemical structure, molecular weight, and pH-dependent capacity of pH-responsive PEG-polyurethane were examined by 1H-NMR, FTIR, gel permeation chromatography (GPC), and an acid-base titration. Moreover, the fluorescent dye fluorescein isothiocyanate was conjugated with PEG-polyurethane by the similar polymerization method and the obtained polymer was measured by ultraviolet visible spectroscopy (UV-vis) and fluorescent spectroscopy. The results indicated that the pH-responsive PEG-polyurethane showed a pH-buffering phenomenon and fluorescent imaging in a range of pH values. As a result, we demonstrated its potential application for optical imaging; however, it is believed that more applications in the areas of biomedicine will be possible owing to its free carboxyl acid terminal residues in the stimuli-responsive polymer. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 129: 846-852, 2013