A pH‐Responsive Gating Membrane System with Pumping Effects for Improved Controlled Release

Abstract

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.

Hybrid alginate beads with thermal‐responsive gates for smart drug delivery

“…2C) become denser than that of the ungrafted ones (Fig. 2A),28 indicating the incorporation of PNIPAAm layer in the pores of the alginate beads. These results confirm that, by using the polymerization method in the present study, PNIPAAm has been grafted onto both the outer surfaces and the inner pores of the hybrid alginate beads.…”

“…The main reason for explaining the higher release rate for semi‐IPN PNIPAAm/alginate beads at 37°C is the precipitation of PNIPAAm above LCST, which leads to the gating effect of the drug. Instead of precipitating from the alginate network as discussed in semi‐IPN PNIPAAm/alginate dual responsive system,20, 21, 28, 30 the shrinkage of PNIPAAm will not break the polymeric network in PNIPAAm‐grafted alginate beads because PNIPAAm is mostly attached in the surface of the pores. As discussed in the literature,30 PNIPAAm‐grafted alginate hydrogels would show suitable mechanical strength without collapsing during repeatable shrinkage and expansion changes, whereas bulk‐grafted or semi‐IPN PNIPAAm/alginate hydrogels collapsed easily.…”

Thermoresponsive Ultrathin Membranes with Precisely Tuned Nanopores for High-Flux Separation

“…Stimuli-responsive polymers have been widely investigated to tailor the physicochemical properties of polymer-modified composites, such as surface wettability and pore structure, triggered by external stimuli like pH, temperature, salt concentration, light, and electronic and magnetic fields. − By far, the modification of stimuli-responsive polymers onto host materials mainly use a “grafting from” approach via living radical polymerization, plasma polymerization, radiation polymerization, and so forth. − Differing from the commonly used “grafting from” approach where initiator is usually introduced onto the surface via chemical treatment in a harsh condition, − in this work, the PEG analogue thermoresponsive copolymer, pyrene-terminated poly­(MEO 2 MA- co -OEGMA), is grafted onto an ultrathin SWCNTs membrane simply by direct adsorption via π–π interaction as schematically depicted in Scheme a. As a mild and effective approach, the noncovalent grafting strategy could protect the inherent structure of the carbon nanotube from being destroyed, and simultaneously, the π–π interaction is strong enough to immobilize the copolymer onto the surface of SWCNTs. − The π–π interaction between grafted polymer and SWCNTs could be further proven by fluorescence spectra (see Figure S1).…”

Swelling-induced mesoporous block copolymer membranes with intrinsically active surfaces for size-selective separation

“…P2VP chains enriched on the pore surface assume a tunable conformation in aqueous media with different pH levels, leading to a correspondingly tunable effective pore size of the membrane. 35,36 As a result, the composite membranes were expected to display a pH-dependent water flux. We measured the water flux of the membrane swelling for 24 h as a function of pH (Fig.…”