Jian-hua Wang

SYNTHESIS OF AMPHIPHILIC COMB-SHAPED COPOLYMERS USED FOR SURFACE MODIFICATION OF PVDF MEMBRANES

The synthesis of a novel amphiphilic comb-shaped copolymer consisting of a main chain of styrene-(N-(4-hydroxyphenyl) maleimide) (SHMI) copolymer and poly(ethylene glycol) methyl ether methacrylate (PEGMA) side groups was achieved by atom transfer radical polymerization (ATRP). The amphiphilic copolymers were characterized by 1H-NMR, Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). From thermogravimetric analysis (TGA), the decomposition temperature of SHMI-g-PEGMA is lower than that of SHMI, and the graft ratio of PEGMA in the SHMI is 18.6%. The experimental results of solubilities showed that SHMI, SHMI-Br and SHMI-g-PEGMA had excellent solubility in polar solvents, such as DMF, DMSO and NMP. SHMI-g-PEGMA had higher solubilities in H2O and methanol, while lower solubility in CHCl3 than SHMI and SHMI-Br. PVDF blend membranes were prepared via the standard immersion precipitation phase inversion process, using amphiphilic SHMI-g-PEGMA copolymer as additives. The morp...

Fabrication of superhydrophilic poly(styrene-alt-maleic anhydride)/silica hybrid surfaces on poly(vinylidene fluoride) membranes.

Superhydrophilic organic/inorganic hybrid surfaces have been fabricated on blend membranes of poly(vinylidene fluoride) (PVDF) and poly(styrene-alt-maleic anhydride) (SMA). The blend membranes were prepared from PVDF/SMA mixed solution with N,N-dimethylacetamide (DMAc) as solvent by immersion-precipitation phase inversion process. The gained blend membranes were immersed into γ-aminopropyltriethoxysilane (APTS) solution to generate SMA/silica hybrid surfaces by the reaction between anhydrides and APTS. The hybrid surfaces chemical compositions, morphologies and hydrophilicity were investigated in detail. It demonstrates that the hybrid surfaces possess micro-nano hierarchical structure and display superhydrophilicity property and good stability. Finally, the reaction and formation mechanism of the superhydrophilicity hybrid surface was discussed.

Fabrication of hydrophilic and sponge-like PVDF/brush-like copolymer blend membranes using triethylphosphate as solvent

Porous PVDF blend membranes with good hydrophilicity and a symmetric structure were prepared by the phase inversion method using amphiphilic brush-like copolymers, P(MMA-r-PEGMA), as hydrophilic additive and triethylphosphate (TEP) as solvent. P(MMA-r-PEGMA) was synthesized by radical polymerization in TEP. Then the obtained amphiphilic copolymer solution was mixed with PVDF and TEP to prepare the dope solution. The effects of P(MMA-r-PEGMA) content and coagulation composition on membrane morphologies were investigated using scanning electron microscopy (SEM). The results demonstrated that, even blended with amphiphilic copolymers, a symmetric structure can be formed. Hollow fiber membranes with a mainly symmetric structure were also fabricated. The dry hollow fiber membranes showed good hydrophilicity, high flux and good rejection performance because of their hydrophilic surface and pores wall.

Fabrication and Performance of a Low Operating Pressure Nanofiltration Poly(vinyl chloride) Hollow Fiber Membrane

A low operating pressure nanofiltration membrane is prepared by interfacial polymerization between m-phenylenediamine (MPDA) and trimesoyl chloride (TMC) using PVC hollow fiber membrane as supporting. A series of PVC nanofiltration membranes with different molecular weight cutoff (MWCO) can be obtained by controlling preparation conditions. Chemical and morphological characterization of the membrane surface was carried out by FTIR-ATR and SEM. MWCO was characterized by filtration experiments. The preparation conditions were investigated in detail. At the optimized conditions (40 min air-dried time, aqueous phase containing 0.5% MPDA, 0.05% SDS and 0.6% acid absorbent, oil phase containing 0.3% TMC, and 1 min reaction time), under 0.3 MPa, water flux of the gained nanofiltration membrane reaches 17.8 L/m2·h, and the rejection rates of methyl orange and MgSO4 are more than 90% and 60%, respectively.

SUPERCRITICAL CARBON DIOXIDE ASSISTED SYNTHESIS OF AMPHIPHILIC GRAFT COPOLYMERS BASED ON POLY(STYRENE-CO-MALEIC ANHYDRIDE) WITH METHOXYL POLY(ETHYLENE GLYCOL) SIDE CHAINS

Supercritical carbon dioxide (scCO2) was used as a reaction medium in synthesizing amphiphilic graft copolymers composed of poly(styrene-co-maleic anhydride) (SMA) backbones and methoxyl poly(ethylene glycol) (MPEG) side chains via esterification. The synthesized copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), 1H-NMR, thermo-gravimetric analysis (TGA) and differential scanning calorimetric analysis (DSC). The gelation phenomenon was suppressed effectively by tuning reaction conditions. The influences of scCO2 temperature and pressure on the conversion of anhydride were investigated. It was found that the highest conversion ratio occurred at 80°C under a constant pressure of 14 MPa or 26 MPa. With the increase of scCO2 pressure, the conversion ratio increased first, and then leveled off. The conversion ratio of anhydride could be controlled by regulating the reaction conditions. It was also revealed that using low molecular weight MPEG brought a high conversion ratio of anhydride.