MANY polymeric hydrogels undergo abrupt changes in volume in response to external stimuli such as changes in solvent composition(1), pH(2), electric field(3) and temperature(4-6). For several of the potential applications of these materials, such as ’smart’ actuators, a fast response is needed. The kinetics of swelling and de-swelling in these gels are typically governed by diffusion-limited transport of the polymeric components of the network in water, the rate of which is inversely poportional to the square of the smallest dimension of the gel(7-9). Several strategies have been explored for increasing the response dynamics(10-14), such as introducing porosity(14). Here we show that we can induce rapid deswelling of a polymer hydrogel by tailoring the gel architecture at the molecular level. We prepare a crosslinked hydrogel in which the polymer chains bear grafted side chains; the latter create hydrophobic regions, aiding the expulsion of water from the network during collapse. Whereas similar gels lacking the grafted side chains can take more than a month to undergo full de-swelling, our materials collapse in about 20 minutes.