External and reversible control of the size and surface energy of the pores in mesoporous architectures has been achieved. The method involves modification of mesoporous silica by atom transfer radical polymerization of N-isopropyl acrylamide (the precursor to a stimuli-responsive polymer). The resulting polymer-grafted particles allow the adsorption and transport of molecular species to be dynamically controlled as illustrated in the Figure for the release of rhodamine 6G from the particles at 50degreesC.