Enhancing the hydrophilicity of polypropylene microporous membranes by the grafting of 2-hydroxyethyl methacrylate via a synergistic effect of photoinitiators

Abstract

Membrane surfaces modified with polymers based on 2-hydroxyethyl methacrylate (HEMA) is promising for hydrophilicity, biocompatibility, and functionality. In this work, the UV-induced graft polymerization of HEMA onto polypropylene microporous membrane (PPMM) was studied using ferric chloride (FeCl 3) and benzophenone (BP) as co-photoinitiators with different methods for the first time. It was found that the conventional photoinitiator, BP, could not initiate the grafting polymerization of HEMA on the PPMM. Incorporation of FeCl 3 into the reaction system remarkably enhanced the grafting of HEMA onto PPMM, which could be ascribed to the “synergistic effect” between Fe 3+ and BP. Results indicated that the maximum grafting degree for the soak method, which added monomer, photoinitiators and membranes in acetone/water mixture together was 2.5-fold greater than that for the adsorption method. Therefore, the grafting degree of HEMA on the membrane surface could be modulated in a wide range through the variation of UV irradiation time, monomer concentration, and BP/FeCl 3 ratio. The poly(HEMA)-modified membrane surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Static water contact angle of the membrane surface indicated a decrease from 145° to 42° with the grafting degree increasing from 0 to 35.67 wt.%. Water drop lied on the modified surface with 35.67 wt.% of grafting degree permeated completely into the membrane pores in 3 s. Furthermore, these poly(HEMA)-tethered membranes showed well protein resistance and potential hemocompatibility due to the enhancement of surface hydrophilicity.