Plasma-Induced Graft Copolymerization of Poly(methacrylic acid) on Electrospun Poly(vinylidene fluoride) Nanofiber Membrane
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文摘
Electrospun nanofibrous membranes (ENM) which have a porous structure have a huge potential for various liquidfiltration applications. In this paper, we explore the viability of using plasma-induced graft copolymerization to reducethe pore sizes of ENMs. Poly(vinylidene) fluoride (PVDF) was electrospun to produce a nonwoven membrane,comprised of nanofibers with diameters in the range of 200-600 nm. The surface of the ENM was exposed to argonplasma and subsequently graft-copolymerized with methacrylic acid. The effect of plasma exposure time on graftingwas studied for both the ENM and a commercial hydrophobic PVDF (HVHP) membrane. The grafting density wasquantitatively measured with toluidine blue-O. The degree of grafting increased steeply with an increase in plasmaexposure time for the ENM, attaining a maximum of 180 nmol/mg after 120 s of plasma treatment. However, theincrease in the grafting density on the surface of the HVHP membrane was not as drastic, reaching a plateau of 65nmol/mg after 60 s. The liquid entry permeation of water dropped extensively for both membranes, indicating a changein surface properties. Field emission scanning electron microscopy micrographs revealed an alteration in the surfacepore structure for both membranes after grafting. Bubble point measurements of the ENM reduced from 3.6 to 0.9um after grafting. The pore-size distribution obtained using the capillary flow porometer for the grafted ENM revealedthat it had a similar profile to that of a commercial hydrophilic commercial PVDF (HVLP) membrane. More significantly,water filtration studies revealed that the grafted ENM had a better flux throughput than the HVLP membrane. Thissuggests that ENMs can be successfully engineered through surface modification to achieve smaller pores whileretaining their high flux performance.

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