| Two kinds of macromolecules, poly (A/-vinyl-2-pyrrolidone) and poly (L-glutamate), were tethered on the surface of polypropylene microfiltration membrane (PPMM) through various methods to improve its hydrophilicity and biocompatibility.A hydrophilic polymer, poly (A/-vinyl-2-pyrrolidone) (PVNP), was tethered on the surface of PPMM by benzoyl peroxide initiated, UV photo-assisted and y-ray pre-irradiation induced graft polymerizations. Results revealed that y-ray pre-irradiation graft polymerization was more efficient in view of the grafting degree. Chemical changes of the membrane surface were confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR) and X-ray photoelectron spectroscopy (XPS). Pure water contact angle on PVNP-grafted PPMM decreased with the increase of grafting degree, which indicated an enhanced hydrophilicity for the modified membrane. Both bovine serum albumin adsorption and static platelets adhesion were measured to evaluate the bio-compatibility of the PVNP-modified PPMM. The statistical amounts of adhered platelets on unit membrane area decreased significantly, which to a certain degree demonstrated that the hemocompatibility of PPMM was improved. N2 permeability and the mean pore diameters of different PPMMs increased at first, then decreased after certain grafting degree. The changes of water flux followed a similar tendency. These indicated that at low grafting degree pore degradation induced by y-ray irradiation had a major effect on permeability, while this was overcompensated by the grafted polymer at high grafting degrees.f^Two facile approaches for the surface modification of PPMM by PVNP macromolecules were developed, which involved the adsorption of PNVP followed by a plasma treatment to immobilize PNVP on the membrane surface, or the treatment of PNVP-adsorbed PPMM with persulfate salt. Chemical and morphological changes of the membrane surface were characterized in detail by ATR/FT-IR, XPS, and water contact angles measurements. Static platelets adhesion on the membrane surface was conducted to evaluate the hemocompatibility of the PNVP-modified PPMM. Results revealed that the plasma treatment time, the amount of adsorbed PNVP, and the persulfate salt content hadillremarkable effects on the immobilization degree of PNVP. Pure water contact angle on the membrane surface decreased with an increase of immobilization degree of PNVP, which indicated an enhanced hydrophilicity for the modified membranes. The statistical amounts of adhered platelets on unit membrane area decreased significantly, which demonstrated that the hemocompatibility of the PNVP-modified PPMMs was improved. Finally, permeation fluxes of pure water and bovine serum albumin solution were measured to evaluate the fouling-resistant properties of the PNVP-modified PPMMs, the results of which had shown an enhancement of antifouling properties for the PPMMs.Two kinds of polypeptide were tethered onto the PPMM surface through a ring opening polymerization of L-glutamate A/-carboxyanhydride initiated by amino groups which were introduced on by ammonia plasma and y-aminopropyl triethanoxysilane treatments. XPS, ATR/FT-IR, scanning electron microscopy (SEM), atomic force microscopy (AFM), together with water contact angle measurements were used to characterize the modified PPMMs. The XPS analyses and ATR/FT-IR spectra demonstrated that polypeptides are actually grafted onto the membrane surface. The wettability of the membrane surface increased at first and then decreased with the increase of polypeptide grafting degrees. Platelets adhesion experiments revealed an enhanced hemocompatibility for the polypeptide modified PPMMs. All these results give evidence that the polypeptide grafting can simultaneously improve the hemocompatibility as well as reserve the hydrophobicity for the membrane, which will provide a potential approach to improve the performance of polypropylene hollow fiber microfiltration membrane used in artificial oxygenator.
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