The Preparation And Studies On Properties Of Environmental Stimuli-response Polymer Membranes

Carboxymethyl polyethersulfone(CMPES) and polyvinylidene fluoride-g-acrylic acid grafting copolymer(PVDF-g-PAA) with environmental stimuli response functions were prepared by chemical grafting method as the polymer matrix of PES and PVDF. The relative content of graft copolymer chemical composition and functional groups were confirmed by infrared spectroscopy and chemical titration. By solution phase inversion method, carboxyl methyl polyethersulfone blend membrane(CPM) and acrylic acid grafted with poly vinylidene fluoride blend membrane(PAM) were prepared with CMPES and PVDF-g-PAA as additive, respectively. The basic properties such as hydrophilic contact angle pore size, porosity and pure water flux of CPM and PAM were measured and the microstructures were observed by scanning electron microscopy(SEM).The equilibrium swelling ratio, swelling reproducibility and flux data under different solution pHs of the blending membrane were verified and analyzed the pH responsiveness of PAM and CPM. The effects of the separation performance of CPM and PAM by environmental stimuli response was studied using the dextran model with different molecular weight labeled with isothio cyanate ester(FITC) was studied.The results indicated that,1. Ion exchange capacity, pore size, porosity, the pure water flux of CPM and PAM increased with increase of CMPES and PVDF-g-PAA additions, hydrophilic contact angle decreased, large hole increased at the bottom of membrane. CPM and PAM had good responsiveness to environment pH good mechanical properties by the swelling reproducibility and the reversibility of the water flux.2. pH response of CPM and PAM were at the range of 3-8 and 3-5, the equilibrium swelling ratio and water flux response value of CPM and PAM increased at pH 3, while CPM and PAM were decreased at pH 8. With the increase of CMPES and PVDF-g-PAA, the equilibrium swelling ratio and water flux of grafting copolymer PAM and CPM gradually increased.3. There were no effect of solution pH and additive dosage for CPM permeation flux of low molecular weight FITC-dextran(MW=500). Equilibrium time of low molecular weight FITC-dextran(MW=4000) for CPM increased with increase of the pH value; permeability for FITC-dextran(MW=40000) of CPM increased with the increase of solution p H, equilibrium time decayed. Equilibrium time decreased with the content of CMPES increase. While permeability for FITC-dextran(MW=40000) of CPM in pH 8 was none. The equilibration time of PAM membrane with low molecular weight FITC dextran(MW=4000) was independent with solution pH; equilibration time of FITC-dextran(MW=40000) on PAM increased with the increase of solution pH; permeability flux for FITC-dextran(MW=70000) of PAM increased with the increase of solution pH, equilibration time prolonged, there was no permeation behavior of PAM FITC-dextran(MW=70000) when the solution above pH 9. Penetration behavior of PAM for FITC-dextran increased with PVDF-g-PAA content. Permeation behavior of CPM and PAM for FITC-dextran showed that the separation applications could be reached by adjusting the composition and structure characteristics.