A thermally induced associative polymer was developed by grafting lower critical solution temperature side chains onto a water-soluble backbone. Based upon the thermodynamic properties of the pendent chains, acting as reversible crosslinkers with varying temperature, such a system was prepared from a poly(ethylene oxide)-modified poly(acrylic acid) (PAA-g-PEO). In aqueous solution this polymer provides an enhancement of the viscosity on heating, the extent of which can be controlled by polymer concentration, grafting ratio and salt concentration.