Novel glycolides with pendent oligo(ethylene oxide) monomethyl ether substituents were synthesized. Subsequent ring-opening polymerization using 4-tert-butylbenzyl alcohol as the initiator and Sn(2-ethylhexanote)(2) as the catalyst yielded homogeneous oligo(ethylene oxide)-grafted polylactides with high molecular weights and low polydispersities. Polymers with short oligo(ethylene oxide) chains (1 or 2 ethylene oxide repeat units) are more hydrophilic than polylactide but insoluble in water, whereas polymers having 3 or 4 ethylene oxide repeat units are water-soluble. Aqueous solutions of polymers with 3 and 4 ethylene oxide repeat units in each pendent chain are thermoresponsive, with lower critical solution temperatures (LCSTs) at 19 and 37 degrees C, respectively. The LCST transitions were confirmed by cloud point measurements, variable temperature dynamic light scattering, and changes in line widths measured by variable temperature H-1 NMR spectroscopy.