Journal of Membrane Science 372 (2011) 285–291 Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Bifunctional hydrogel coatings for water purification membranes: Improved fouling resistance and antimicrobial activity Young-Hye La a,∗ , Bryan D. McCloskey b,1 , Ratnam Sooriyakumaran a , Ankit Vora a , Benny Freeman b , Majed Nassar c , James Hedrick a , Alshakim Nelson a , Robert Allen a a IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, United States b University of Texas at Austin, Center for Energy and Environmental Resources, 10100 Burnet Road, Building 133, Austin, TX 78758, United States c King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442, Saudi Arabia article info Article history: Received 15 December 2010 Received in revised form 9 February 2011 Accepted 9 February 2011 Available online 16 February 2011 Keywords: Anti-fouling Antimicrobial Hydrogel Poly(ethylene glycol) Ammonium salt abstract Bifunctional hydrogel materials having both fouling resistance and antimicrobial activity were pre- pared by the photopolymerization of polyethylene glycol diacrylate (PEGDA) and a functional monomer containing ammonium salt (RNH 3 Cl) in the presence of a photoinitiator. Water was added to the prepoly- merization mixture to increase the solubility of the RNH 3 Cl monomer and to control the cross-linking density of the UV-cured films. The water uptake and permeability of the resulting films were easily con- trolled by manipulating the composition ratio of the PEGDA and RNH 3 Cl monomers and by varying the water content in the prepolymerization mixture. Extremely high water uptake (up to 900%) and per- meability (∼200 L mm -2 h -1 atm -1 or above) values were observed for the films prepared by adding 80% (w/w) water into the prepolymerization mixtures of PEGDA and RNH 3 Cl (weight ratio = 1:1 or 2:1). PSF UF membranes coated with these water-absorbing hydrogel materials showed excellent anti-fouling efficiency in cross-flow filtration tested using an oil–water emulsion or a bovine serum albumin (BSA) solution as the feed. Antimicrobial activity of the hydrogel materials was also demonstrated by a case study employing E. coli. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Membrane treatment processes, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), have been widely used to purify water as a result of their simple operation and competitive energy efficiency [1]. In particular, low pressure UF membranes, with physical pores in the size range of 0.001–0.1 m, have become more attractive for various industrial applications such as oil/water emulsion separation [2,3] beverage production [4], dairy/food processing [5], and membrane bioreac- tor (MBRs) waste water treatment [6,7] UF is also considered an effective pretreatment solution for RO-desalination processes to remove turbidity and microbiological contaminants [8]. In general, hydrophobic polymers, such as polysulfones (PSF), polyethersulfones (PES), polyvinylidenefluoride (PVDF) and poly- acrylonitrile (PAN), are often used as separation layers of commercial UF membranes due to their strong chemical and mechanical stability. However, one of the major issues with using ∗ Corresponding author. Tel.: +1 408 927 1256; fax: +1 408 927 3310. E-mail address: yna@us.ibm.com (Y.-H. La). 1 Current address: IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, United States. hydrophobic separation layers for membranes is the strong inter- action with hydrophobic chemicals and biological contaminants, including natural organic matters (NOM), emulsified oils, sus- pended solids and microorganisms [9–12]. This causes significant internal (pore clogging) and external (surface deposition) mem- brane fouling, resulting in increased operational costs arising from higher transmembrane pressure requirements, and more frequent membrane cleaning and membrane replacement [11,13–14]. Therefore, recent research has focused on surface hydrophiliza- tion of UF membranes to improve inherent membrane anti-fouling properties. Surface-initiated grafting of hydrophilic functional monomers has been reported as one way to modify hydropho- bic UF membranes. For surface grafting, UF membranes have to be pretreated with UV, plasma, or chemical agents to create reactive sites on the membrane surface, and in most cases, grafting occurs only on the top-surface of membranes so that internal pores are still susceptible to fouling [15–17]. Self-segregation of hydrophilic moieties has been demonstrated as an effective way for mem- brane surface and internal pore modification. In this method, an amphiphilic copolymer composed of hydrophilic and hydrophobic moieties is blended with a membrane casting solution containing a hydrophobic base material. During the phase inversion process, the amphiphilic copolymer typically segregates to the polymer–water interfaces to afford a hydrophilic surface [18,19]. Alternatively, 0376-7388/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2011.02.005