Ammonification Of Methoxy PolyEthylene Glycol And Graft Of Poly(Ethylene Glycol) Brush On Polysulfone Porous Membrane

As a membrane material used in plasmapheresis, polysulfone (PSF) has advantages in aspects of biocompatibility, chemo stability, mechanical strength, which make it popular in the field of biomedical materials. But the hydrophobic of PSF would cause serious fouling during the process of plasmapheresis, resulting in the irreversible adsorption of proteins on membranes, and reducing their permeability at least 30%. Once the conformation of the absorbed proteins changed, severe injuries would take place, such as blood coagulation and activation of immunosystem. In order to prevent the fouling of proteins, most efforts of current researches are focused on hydrophilic modification of membrane surfaces. Through the hydrophilic modification, researchers expect to obtain biocompatible surfaces and maintain the intrinsic bulk properties of the material. Among these researches, physisorption and covalent attachment of poly(ethylene glycol) on surface of various materials has long been studied widely and there're a lot of papers and patents being published in the past three decades. In 1990's, it was found that the capability of mono-layered PEG brush to resist protein fouling was much greater than that of multi-layered PEG. In this paper, spin coated PSF films were used as the material to be surface-modified by grafting brush-like PEG with 4-azidobenzoic acid photocoupler. Achievement of UV irradiation grafting of MPEG on polysulfone sheets (or films) may provide thefoundation for further advancement in tethering brush-like PEG on ultrafiltration Psf hollow fiberBy using potassium naphthalene as catalyst, MPEG-OTs was synthesized from MPEG and 4- tolylsulfonyl chloride. According to Gabriel's method, MPEG-NH2 was synthesized from MPEG-OTs and potassium phthalimide, and purified by means of recrystallization in dichloromethane//ether mixture at least three times until crystal pure product obtained. Yielded 81%.On the other hand, 4-azidobenzoic acid (AzBA) which was prepared by the addition of sodium azide to the acidic diazonium chloride from 4-aminobenzoic acid was purified in ethanol water solution (ethanol: H2O= 6(v): 4(v)), and got 77% yield, crystal pure. Furthermore. AzBA was grafted to the polysulfone porous membranes under the following conditions: (1) in the darkroom, adjust the concentration of AzBA to 0.08mol/l, with the amount was l00ul (2) incubated under N2 atmosphere for 16 hrs at 40癈, (3) keep Psf films wet during UV irradiation for 40min. By the results of element analysis, AzBA has been grafted on polysulfone successfully. Then used l,3-(3-dimethylaminopropyl)ethylcarbodiimide(EDC) as photocoupler, MPEG-NH2 through its amino group reacted with the -COOH of AzBA forming amide bond and grafted on.From water contact angle and protein absorption measurements, there was a great improvement of hydrophilicity and protein antifouling property of the PSF sheets (or films) grafted with MPEG. Efficiency of grafting by X-ray photoelectron spectroscopy was 100%. With atomic force microscope (AFM), obvious differences in the shape and the relative moduli were found between surfaces of MPEG grafted PSF membrane. Evidences inferred sequential pathway was coupled with a monolayered PEG brush.