Precise control of surface physicochemical properties for electrospun fiber mats by surface-initiated radical polymerization

Abstract

Non-woven fiber mats were fabricated with the electrospinning method using poly(methyl methacrylate)-co-poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) in various solvents. The surface morphology of the electrospun fibers depended on the solvent vapor pressure and polymer concentration. Surface-initiated atom transfer radical polymerization (ATRP) with 3-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatopropanesulfonate), 2-hydroxyethyl methacrylate or 2-(perfluorooctyl)ethyl acrylate generated surface-grafted polymers, as determined by X-ray photoelectron spectroscopy. Scanning electron microscopic observation revealed that the apparent fiber morphology did not change upon modification. The atomic force microscopic images of the grafted fiber cross-sections indicated that monomers and solvents penetrated slightly into the fibers and polymerization occurred at both internal and external initiation sites. Physicochemical properties, such as contact angle, hydrophobicity and hydrophilicity, and wettability, could be altered by the proper selection of substrates (spin-coated flat films or the variously prepared non-woven fiber mats). We have successfully prepared hydrophilic and hydrophobic fiber surfaces by a combination of the electrospinning protocol and surface-initiated ATRP. Functional non-woven fiber mats were prepared by combining the electrospinning method and surface-initiated atom transfer radical polymerization (ATRP). The surface-initiated ATRP of 3-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatopropanesulfonate), 2-hydroxyethyl methacrylate and 2-(perfluorooctyl)ethyl acrylate proceeded successfully from the fiber surface of poly(methyl methacrylate)-co-poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) without any structural changes. A grafted layer after the surface-initiated ATRP was observed by atomic force microscopy. Static contact angles against water were also evaluated to discuss the relationship between the roughness of the electrospun non-woven fiber mats and wettability.