Construction and characterization of three-dimensionally ordered macroporous polystyrene equipped with pH-responsive switchable windows

Three-dimensionally ordered macroporous (3DOM) materials have a large pore volume and a uniformly distributed pore size. The macropores are interconnected with each other via window'' channels. A novel pH-responsive carrier system based on 3DOM material has been constructed by grafting pH-responsive polymeric chains from the pore wall of 3DOM cross-linked polystyrene (3DOM CLPS) via surface-initiated atom transfer radical polymerization to control the on-off action of the window'' channels. The grafted amounts can be controlled by variation of the solvent and the graft polymerization time. The functionalized 3DOM CLPS has a high pore volume and can store more guest molecules. Guest molecules such as vancomycin can be stored and released from the macropores of the functionalized 3DOM CLPS by changing pH values at will. The on-off action of windows'' at different pH values was confirmed by the storage-release experiments, which demonstrate that the level of vancomycin release from the functionalized 3DOM CLPS is strongly dependent on the pH value. The storage-release experiments of 3DOM CLPS-g-PAA with different grafted amounts and the 3DOM CLPS without grafting a polymer chain indicate that the introduced pH-responsive polymer chains act as a permeation valve on the connected windows. We envision that the new 3DOM material equipped with pH-responsive switchable windows can play a significant role in developing new generations of intelligent delivery materials, intelligent chromatographic sampling, and other molecular machines.