A pH-responsive gating membrane system with pumping effects for improved controlled release

In this study, we report on a novel composite membrane system for pH-responsive controlled release, which is composed of a porous membrane with linear grafted, positively pH-responsive polymeric gates acting as functional valves, and a crosslinked, negatively pH-responsive hydrogel inside the reservoir working as a functional pumping element. The proposed system features a large responsive release rate that goes effectively beyond the limit of concentration-driven diffusion due to the pumping effects of the negatively pH-responsive hydrogel inside the reservoir. The pH-responsive gating membranes were prepared by grafting poly(methacrylic acid) (PMAA) linear chains onto porous polyvinylidene fluoride (PVDF) membrane substrates using a plasma-graft pore-filling polymerization, and the crosslinked poly(N,N-dimethylaminoethyl methacrylate) (PDM) hydrogels were synthesized by free radical polymerization. The volume phase-transition characteristics of PMAA and PDM were opposite. The proposed system opens new doors for pH-responsive "smart" or "intelligent" controlled-release systems, which are highly attractive for drug-delivery systems, chemical carriers, sensors, and so on.