Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 2, 2008
Publication Date: February 9, 2009
Citation: Liu, S.X., Kim, J., Kim, S., Singh, M. 2009. The Effect of Polymer Surface Modification on Polymer-protein Interaction via Interfacial Polymerization. Journal of Applied Polymer Science. 112:1704-1715. Interpretive Summary: Membrane fouling caused by protein adsorption on hydrophobic (water-hating) polyethersulfone (PES) membranes can be mitigated by modification of membrane surface such as making membrane surface more hydrophilic (water-loving) through incorporating hydrophilic polymers or functional groups onto the virgin membranes' surfaces. In this study, we investigated interfacial polymerization as a technique of making PES surface more hydrophilic. Hydrophilic polymers, poly(vinyl alcohol) (PVA), polyethylene glycol (PEG), and chitosan were used to form a hydrophilic layer on top of the PES membrane. Modified PES membranes were tested by various analytical instruments. The results of these instrumental analyses indicated that the modified PES membranes are more hydrophilic. The subsequent experiments using the modified membranes show the reduction of proteins adsorption on the membranes for about 30% to 35%. The research will benefit the development of new membranes used for economically extracting value added food or industrial materials from dried distillers grains (DDG), a by-product of corn-based biofuel production.
Technical Abstract: Membrane separation is an important processing technology used for separating food ingredients and fractionating value-added components from food processing by-products. Long-term performance of polymeric membranes in food protein processing is impeded by formation of fouled layers on the membrane surface as a result of protein adsorption onto the membrane surface. Surface modification of synthetic membranes, i.e., changing surface characteristics to reduce protein adsorption permanently, is one of innovative ways of reducing the fouling of membrane surfaces. In this study, surface modification of flat sheet ultrafiltration membrane, polyethersulfone (PES), was investigated in improving the hydrophilicity of PES surfaces thereby reducing adsorption of the protein caused by hydrophobic-hydrophobic interaction between the protein and the membrane. Hydrophilic polymer grafting through thin film composite using interfacial polymerization was employed to improve the hydrophilicity of the commercial PES membranes. Poly(vinyl alcohol) (PVA), polyethylene glycol (PEG), and chitosan were chosen as hydrophilic polymers to graft on PES membrane because of their excellent hydrophilic property. Modified PES membranes were characterized by contact angle, FTIR, XPS, and AFM. Contact angles of modified PES membranes were reduced by 25% to 40% of that of the virgin PES membrane. XPS spectrum supported that the PES membranes were successfully modified by interfacial polymerization. Tapping mode AFM was used to examine the changes in surface topography of modified PES membranes. The PES membranes modified by interfacial polymerization showed lower roughness (from 1.2 nm to 2.0 nm) than that of virgin PES membrane (2.1 nm). The results of these instrumental analyses indicated that the PES membranes were successfully enhanced hydrophilically through interfacial polymerization. The protein adsorption on the modified membranes was reduced by 30% to 35% as a result of surface modification of the PES membranes using interfacial polymerization technique.