Environmental stimuli-responsive membranes have many latent applications in numerous fields, for example, chemical/biological separations, water treatment, drug delivery, self-cleaning material and chemical sensor. In this study, a pH-responsive membrane with in-situ assembled stimuli-responsive microgels on membrane surface and internal channels wall was fabricated by the coagulation step of the phase-inversion process. Interestingly, it was found that poly(4-vinyl pyridine) (P4VP) microgel can be mobilized onto the membrane surface by using an acidic coagulation bath. Meanwhile, the membrane-based materials with different hydrophobic properties showed a great effect on the migration of microgel onto the channel surface. The inner pores of these responsive membranes can self-adjust its size with the changes of outside pH stimulus. Moreover, the gate-controlled water permeability of pH-responsive membranes was explored at the pH interval from pH 2 to pH 6. Investigations revealed that the P4VP microgel-assembled membrane had excellent pH-responsive performance. In addition, these pH-responsive membranes with embedded microgels on surface and inner pores wall also exhibited excellent reversible behaviors and self-cleaning properties.
Superhydrophilic oil-water separation membranes exhibit fixed interfacial properties, which limits their ability to withstand oil fouling. Enhancing the in-situ anti-fouling performance of membranes dynamically at the interface is challenging. Here, a structurally adjustable pH-responsive membrane for oil-water separation was prepared, combined with patterned silver gel to impart conductivity. Acting as a cathode, this membrane electrolyzes water to generate OH − ions that directly regulate the interfacial pH. The generated OH − ions trigger the responsive layers' contraction, which results in the expansion of the membrane's pore size. Such structural adjustments could shorten the oil-water-solid three-phase contact line of pinned oil droplets to reduce the adhension force, creating interfacial disturbances that enhance the anti-fouling capabilities of membrane. By this way, lubricants and crude oils adhered to the membrane could be de-wetted in 32 s without other assistance. Meanwhile, the expansion of the membrane's pore size increases the washing efficiency. The flux recovery rate after 300 min long-term cycling can reach up to 97.6 % without additional reagents. The fabricated anti-fouling membrane significantly improves separation efficiency and holds great potential for applications in oily wastewater treatment.
Linlin Li,Li Xia,Feng Xiao,Yewen Xiao,Wei Ji,Baocai Xu,Hualin Wang
Using novel active food packaging has gradually become a daily necessity in terms of impeding microbial contamination. Here, an antimicrobial photodynamic inactivation (PDI) pH-responsive film is developed by incorporating aloe-emodin (AE) into a vehicle of gelatin/chitosan (GC). Besides enhancement in hydrophobicity, the well-dispersed crystals of AE in the GC matrix by hydrogen bonding can upgrade the film's mechanical strength and barrier. The matrix is capable of regulating the release of AE in response to acidic stimuli by a combination mechanism of diffusion and polymer relaxation. Being benefitted from the inherent bioactivity of AE and the PDI activity under visible light irradiation (i.e., 456 nm), the target film of GC-AE2 has excellent antibacterial effect towards Staphylococcus aureus and Escherichia coli , showing bacterial viability of 9.93 ± 1.33 % and 14.85 ± 1.16 %, respectively. Furthermore, the film can effectively thwart Botrytis cinerea infection in cherry tomatoes, demonstrating its potential in preventing the microbial spoilage of postharvest fruits.
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