Surface zwitterionicalization of poly(vinylidene fluoride) membranes from the entrapped reactive core-shell silica nanoparticles.

We demonstrate the preparation and properties of poly(vinylidene fluoride) (PVDF) filtration membranes modified via surface zwitterionicalization mediated by reactive core-shell silica nanoparticles (SiO2 NPs). The organic/inorganic hybrid SiO2 NPs grafted with poly(methyl meth acrylate)-block-poly(2-dimethylaminoethyl methacrylate) copolymer (PMMA-b-PDMAEMA) shell were prepared by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization and then used as a membrane-making additive of PVDF membranes. The PDMAEMA exposed on membrane surface and pore walls were quaternized into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) using 1,3-propane sultone (1,3-PS) as the quaternization agent. The membrane surface chemistry and morphology were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The hydrophilicity, permeability and antifouling ability of the investigated membranes were evaluated in detail. It was found that the PSBMA chains brought highly-hydrophilic and strong fouling resistant characteristics to PVDF membranes due to the powerful hydration of zwitterionic surface. The SiO2 cores and PMMA chains in the hybrid NPs play a role of anchors for the linking of PSBMA chains to membrane surface. Compared to the traditional strategies for membrane hydrophilic modification, the developed method in this work combined the advantages of both blending and surface reaction.

Versatile antifouling polyethersulfone filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive.

Here we describe the development of versatile antifouling polyethersulfone (PES) filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive. Amphiphilic polyethersulfone-block-poly(2-hydroxyethyl methacrylate) (PES-b-PHEMA) was beforehand designed and used as the blending additive of PES membranes prepared by phase inversion technique. The surface enriched PHEMA blocks on membrane surface acted as an anchor to immobilize the initiating site. Poly(sulfobetaine methacrylate) (PSBMA) were subsequently grafted onto the PES blend membranes by surface-initiated atom transfer radical polymerization (SI-ATRP). The analysis of surface chemistry confirmed the successful grafting of zwitterionic PSBMA brushes on PES membrane surface. The resulted PES-g-PSBMA membranes were capable of separating proteins from protein solution and oil from oil/water emulsion efficiently. Furthermore, the modified membranes showed high hydrophilicity and strongly antifouling properties due to the incorporation of well-defined PSBMA layer. In addition, the PES-g-PSBMA membranes exhibited excellent blood compatibility and durability during the washing process. The developed antifouling PES membranes are versatile and can find their applications in protein filtration, blood purification and oil/water separation, etc.

[Evaluation on intervening efficacy of health education on accidental suffocation and drowning of children aged 0 - 4 in countryside].

OBJECTIVE: The main causes of death in children aged 0 - 4 were accidental suffocation and drowning which had a significant relation with parents' lack of prevention knowledge and effective measures. By comparing parents' acknowledge and behavior in preventing accidental suffocation and drowning and the mortality rate of accidental suffocation and drowning after intervening with those before the intervening, evaluation was made on intervening efficacy of health education. METHODS: Six counties in north Jiangsu were involved in the survey. Two townships drawn from each county were divided into the intervened group and the controlled group. Health education was carried out in the intervened group for one year in 2000. Twenty to 30 parents of infants and children aged 1 - 4 drawn randomly from every township in the intervened group were taken as investigation subjects before and after intervening, and a questionnaire was made for them to answer. Meanwhile, the mortality rates of accidental suffocation and drowning were measured. RESULTS: Followed by health education for a year, the parents' opinion about whether unintentional injury can be avoided or not has changed from 18.8% to 20.5% to 1.8% - 2.9%, and parents' knowledge about how to give first aid in spot has increased from 11.1% - 13.5% to 41.1% - 56.8%. The parents' behavior that not sleeping with their infants in the same beds and not tying infants in a candle with blanket, and setting up fence beside pools and rivers has increased by 75.7%, 61.5% and 61.2%, respectively, while their relative knowledge has increased by 212.7% and 194.3%. In the intervened group, the mortality rates of infants' accidental suffocation per 100,000 has fallen from 487.8 to 71.2, dropped by 85.4%; and the mortality rates of drowning in children aged 1 - 4 per 100,000 has fallen from 60.0 to 36.2, dropped by 39.7%. In comparison, in the controlled group, the mortality rates of infants' accidental suffocation per 100,000 has fallen from 344.1 to 276.4, dropped by 19.7%; and the mortality rates of drowning in children aged 1 - 4 per 100,000 has increased by 26.3%, from 51.7 to 65.3. CONCLUSION: Health education to parents is an effective intervening measure for prevention of accidental suffocation and drowning. The goal of health education should be to change inadequate behavior and dangerous environment in which unintentional injury is easily happened. The intervening measures that not sleeping with their infants in the same beds and not tying infants in a candle with blanket, and putting up fence beside pools and rivers are feasible and practicable.