Synthesis of membrane adsorbers via surface initiated ATRP of 2-dimethylaminoethyl methacrylate from microporous PVDF membranes

Surface-initiated atom transfer radical polymerization(SI-ATRP) was used to tether poly(2-dimethylaminoethyl methacrylate)(PDMAEMA) onto microporous PVDF membranes in order to synthesize membrane adsorbers for protein adsorption. The alkaline treatment and bromine addition reaction were used to anchor ATRP initiators on membrane surface. Then PDMAEMA was grafted from the membrane surface via SI-ATRP. Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM) revealed the chemical composition and surface topography of the PVDF-g-PDMAEMA membrane surfaces. These results showed that PDMAEMA was grafted from the membrane surface successfully and a grafting yield as high as 1500 μg/cm2 was achieved. The effects of the grafting time and the density of initiators on the static and dynamic binding capacity of bovine serum albumin(BSA) were systematically investigated. Both the static and dynamic binding capacities increase with the bromination and polymerization time. However, the benefits of the initiator density on binding capacities are limited by the graft density of PDMAEMA chains.     

SURFACE MODIFICATION OF POLYPROPYLENE MICROPOROUS MEMBRANES BY THE ADSORPTION OF NON-IONIC SURFACTANTS

Surface modification by physical adsorption of a series of non-ionic surfactants including Tween 20, Tween 40, Tween 60, Tween 80 and Tween 85, was accomplished on polypropylene microporous hollow fiber and flat membranes. The adsorption curve of the membrane surface was analyzed by weight measurements and the typical results showed a twoplatform character similarly. Differences in the degree and curve shape of adsorption resulting from such factors as concentration, temperature, as well as water cleaning time were observed for Tween 85 among other Tweens. Attenuated total reflection - Fourier transform infrared spectroscopy analysis and field emission scanning electron microscopy observation showed that the adsorption of Tween on polypropylene microporous membrane （PPMM） is effective and occurs mainly in the pores of PPMMs at low adsorption amount, and on the membrane surface also at high adsorption value.     

SURFACE MODIFICATION OF MICROPOROUS POLYPROPYLENE MEMBRANES BY GRAFT POLYMERIZATION OF N,N-DIMETHYLAMINOETHYL METHACRYLATE

Surface modification of microporous polypropylene hollow fiber membranes was performed by radical-induced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA). The influences of temperature, monomer concentration and pre-adsorbed amount of benzoyl peroxide on grafting degree were studied respectively. It was found that the appropriate graft temperature was 75℃, at which the grafting degree was the highest and the hydrolytic decomposition of DMAEMA the lowest. Scanning electron photomicrography and the average pore diameters of the modified membranes demonstrated that part of the micropores on the membrane surface was plugged by the grafted polyDMAEMA chains, especially at high grafting degree. Contact angle and water swelling experiments showed that a moderate grafting degree could improve the hydrophilicity of the membranes. In the range of I 1.3%o-12.0% grafting degree, the water swelling percentage reached its maximum (51.1%) and the contact angle reached its minimum (74 degrees). The bovine serum albumin (BSA) adsorption experiment indicated that the grafted polyDMAEMA had a dual effect on protein adsorption. At the first stage, the BSA adsorption decreased with increasing of DMAEMA grafting degree. As the interaction between BSA and polyDMAEMA on membrane surface increased, the BSA adsorption increased with increasing of DMAEMA grafting degree.     

Antibacterial poly(D,L-lactide) (PDLLA) fibrous membranes modified with quaternary ammonium moieties

<正>Antibacterial poly(D,L-lactide)(PDLLA) fibrous membranes were developed via electrospinning,followed by surface modification which involved plasma pretreatment,UV-induced graft copolymerization of 4-vinylpyridine(4VP) and quaternization of the grafted pyridine groups with hexylbromide.The success of modification with quatemized pyridinium groups on the PDLLA fibrous membranes was ascertained by X-ray photoelectron spectroscopy(XPS).The antibacterial activities of these membranes were assessed against Gram-positive Staphylococcus aureus(S.aureus) and Gram-negative Escherichia coli(E.coli).The PDLLA fibrous membranes modified with quaternized pyridinium groups showed antibacterial efficiency against both bacteria as high as 99.999%.The results demonstrated that the antibacterial activity was based on the interaction of the positive charge of pyridinium group and negatively charged cell membrane of bacteria, resulting in loss of membrane permeability and cell leakage.     

PREPARATION AND CHARACTERIZATION OF ION EXCHANGE MEMBRANES BASED ON POLYVINYLIDENE FLUORIDE

A new ion exchange membrane based on polyvinylidene fluoride (PVDF) and sulfonated poly(styrenedivinylbenzene) was prepared by in-situ polymerization. The incorporation of sulfonic groups into the polyvinylidene fluoride composite membrane was confirmed by infrared spectroscopy (IR), ion exchange capacity (IEC) and energy dispersive X-ray analysis (EDAX). Area resistance, IEC and water uptake of the treated membrane were evaluated. When area resistance in NaCl aqueous solution at 25℃, IEC is as high as 2.43 millimoles per gram of the wet membrane. The hydrophilicity of PVDF membrane is also significantly improved after treatment. When 60% of crosslinked membrane was sulfonated at 80℃ for 6 h, water uptake of the treated membrane can attain 64.7%.     

Preparation and Properties of Poly(aryl ether sulfone ketone) Ultrafiltration Membrane Containing Fluorene Group for High Temperature Condensed Water Treatment

Novel poly(aryl ether sulfone ketone)s(PAESK) were synthesized from bisphenol A(BPA),9,9′-bis(4-hydroxyphenyl)fluorene(BHPF),4,4′-dichlorodiphenylsulfone(DCS) and 4,4′-difluorobenzophenone(DFB) via nucleophilic substitution polymerization,which were subsequently used to fabricate ultrafiltration membrane by phase-inversion method for high temperature condensed water treatment.The obtained high molecular weight co-polymers with fluorene group with good solubility and good thermal stability,can be easily cast into flexible,white and non-transparent flat films.The influence of molar ratio of BPA and BHPF on the properties of the prepared co-polymers and membranes was investigated in detail.SEM study of the morphology of the membranes indicated that the prepared membranes possessed homogeneous pores on the top surface and were sponge-like or finger-like in cross-section.Pure water flux of the membranes increased from 71.87 L·m~(-2)·h~(-1) to 247.65 L·m~(-2)·h~(-1),while the retention of BSA decreased slightly,and the water contact angle decreased from 82.1° to 55.6° with the PVP concentration from 0 wt% to 10 wt%.With increasing concentration of PVP,the mechanical properties of membranes decreased,while the thermal stability increased.The permeate flux measurement showed that the PAESK membrane had the potential for high temperature condensed water treatment.     

微波场中A型分子筛及分子筛膜合成的研究

Effects of aging time and alkalinity as well as cation concentration(Na⁺) on the synthesis of A type zeolite and zeolite membrane were investigated in this paper. The results showed that aging time for synthesis of A type zeolite and zeolite membrane had remarkable influence and alkalinity could accelerate the formation of zeolite but was disadvantage to zeolite membrane synthesis. Cation concentration(Na⁺) also couldn′t accelerate the synthesis of zeolite and zeolite membrane but it was probable an important factor to accelerate crystal growth .Moreover, more compact zeolite membranes could be synthesized by this method while the thickness of membrane was thinner than that of convention. Zeolites and zeolite membranes were characterized by XRD, TEM as well as IR characterization techniques.     

APPLICATION OF NONIONIC TEMPERATURE SENSITIVE HYDROGEL FOR CONCENTRATION OF PROTEIN AQUEOUS SOLUTION

Six different N-alkyl substituted acrylarnide nonionic hydrogels were prepared and their swelling characteristics were measured. Poly N-isopropyl acrylamide (PNIPA) and poly N-n-propyl-acrylamide (PNNPA) temperature sensitive hydrogels were chosen as the nonionic temperature sensitive hydrogels for concentration of very dilute aqueous protein solution. The separation properties of PNIPA and PNNPA hydr0gels with different network dimensions were studied and the modification of the hydrogels was surveyed in order to decrease their surface adsorption of protein molecules. The experimental results of the concentration of BSA (Bovin serum albumin) dilute aqueous solution by hydroxylpropyl methacrylate (HPMA) copolymerized PNIPA hydrogel were given. The value and the limitation of concentration of dilute aqueous protein solution by this method was evaluated.     

Development of proton-conducting membrane based on incorporating a proton conductor 1,2,4-triazolium methanesulfonate into the Nafion membrane

In this paper, 1,2,4-triazolium methanesulfonate(C2H4N+3CH3SO-3, [Tri][MS]), an ionic conductor, was successfully synthesized. It exhibited high ionic conductivity of 18.60 m S cm-1at 140CdSC and reached up to 36.51 m S cm-1at 190CdSC. [Tri][MS] was first applied to modify Nafion membrane to fabricate [Tri][MS]/Nafion membrane by impregnation method at 150CdSC. The prepared composite membrane showed high thermal stability with decomposed temperature above 200CdSC in air atmosphere. In addition, the membrane indicated good ionic conductivity with 3.67 m S cm-1at 140CdSC and reached up to 13.23 m S cm-1at 180CdSC. The structure of the [Tri][MS] and the composite membrane were characterized by FTIR and the compatibility of [Tri][MS] and Pt/C catalyst was studied by a cyclic voltammetry(CV) method. Besides, the[Tri][MS]/Nafion membrane(thickness of 65 μm) was evaluated with single fuel cell at high temperature and without humidification. The highest power density of [Tri][MS]/Nafion membrane was 3.20 m W cm-2at 140CdSC and 4.90 m W cm-2at 150CdSC, which was much higher than that of Nafion membrane.     

STUDIES ON THE PERMEABILITY OF P VC/EBBA OVERLAPPED ULTRATHIN COMPOSITE MEMBRANES MODIFIED BY PLASMA-POLYMERIZATION WITH FLUOROCARBON MONOMERS

The PVC/EBBA ultrathin composite membranes with thickness of about 100 nm were prepared by spreading the solution on water surface. The overlapped composite membrane showed a characteristic aggregation structure in which the polymer matrix exists as a three-dimensional spongy network and the liquid crystal domains werc observed. Tne surface modification for the overlapped membranes was carried out by means of plasma-polymerization with the monomers of fluorocarbon compounds. Both Arrhenius plots of permeability coefficients for oxygen ((?)_O_2) in the membrane samples before and after modification showed significant increase in the vicinity of the T_(KN) of EBBA.