Journal of Membrane Science 390–391 (2012) 1–11 Contents lists available at SciVerse ScienceDirect Journal of Membrane Science jo u rn al hom epa ge: www.elsevier.com/locate/memsci Searching for novel membrane chemistries: Producing a large library from a single graft monomer at high throughput Philip S. Yune a , James E. Kilduff b , Georges Belfort a,∗ a Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, USA b Department of Civil and Environmental Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA a r t i c l e i n f o Article history: Received 18 August 2011 Received in revised form 17 October 2011 Accepted 19 October 2011 Available online 18 November 2011 Keywords: High throughput Surface modification UV-induced grafting Ultrafiltration Epoxy Amine a b s t r a c t Glycidyl methacrylate (GMA) was grafted on poly(ether sulfone) (PES) membranes via photo-initiated graft polymerization (PGP). 25 amine monomers were introduced at 90 ◦ C for 12 h to facilitate the epoxy ring opening reaction on GMA grafts. Our high throughput platform (HTP) approach was used to test and screen for desired surface characteristics. Analysis of the fouling index (ℜ, flux reduction upon static fouling), surface adsorption index (¯ q, surface adhesion of protein) and sieving coefficient (S 0 , protein permeation upon dynamic fouling) were used as criteria of success. Bovine serum albumin (BSA) and lysozyme (LYS) at 1 mg mL -1 were used as model foulants. Six of the 25 grafted species were identified as “winners” by exhibiting lower ℜ and ¯ q (i.e. lower flux decline and protein adhesion on membrane surfaces, respectively) compared with GMA grafting alone (internal control) or with poly(ethylene glycol) (PEG) grafting. S 0 was plotted against permeability in order to analyze the flux-selectivity behavior due to grafting and fouling. Diethanolamine was resistant both to BSA with ℜ = 0.31 ± 0.12, ¯ q = 0.68 ± 0.11, S 0 = 0.86 ± 0.03, and LYS with ℜ = -1.96 ± 0.26, ¯ q = 0.71 ± 0.03 and S 0 = 0.65 ± 0.27. The conversion of the epoxy group by the reaction with amine was confirmed with the degree of grafting analysis using FTIR/ATR. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Poly(ether sulfone) (PES), a widely used filtration membrane material in bioprocessing, is stable, easy to cast and clean and rel- atively inexpensive [1,2]. However, because of its apolar nature, proteins are attracted to its surface causing substantial fouling and drop in performance [3]. Researchers are continually searching for low fouling surfaces that impart protein resistance. Numerous dif- ferent surface modification techniques including photo-induced graft polymerization (PGP) [4–8], plasma treatment [9–12] and other approaches [13–16] have been pursued. Among them, PGP was chosen because it is a simple and relatively inexpensive method that is suitable for scale-up [5]. Moreover, PES produces radicals upon exposure to UV irradiation without a photoinitiator, which confers further merit in laboratory and commercial scale production [17]. To address fouling resistance, the Belfort group has combined the photo-graft polymerization (PGP) methodology with a novel high throughput platform (HTP) to modify PES sur- faces that repel proteins and natural organic matter [18–22]. The ∗ Corresponding author. Tel.: +1 518 276 6948; fax: +1 518 276 4030. E-mail address: belfog@rpi.edu (G. Belfort). HTP–PGP technique provides a fast, reproducible and statistically reliable surface modification and diagnosis method. Glycidyl methacrylate (GMA) is inherently protein-resistant and its fouling resistance has been known and studied by previ- ous researchers [23–25]. Besides its protein-resistant nature, its epoxy moiety is of interest for its ability to form covalent bonds with other functional groups by ring-opening poly-condensation. Because of this property, GMA has been used for diverse applica- tions such as with a spacer arm, with cross-linking chains or with co-polymer blocks [26–30]. The epoxy group in GMA readily reacts with primary or secondary amine groups under basic condition and elevated temperature as seen in Fig. 1A. Although amines can serve as hydrogen bond donor by car- rying a partial positive charge, it also can serve as hydrogen bond acceptor due to the presence of free electrons. Amines are known to have ability to repel proteins by serving as hydrogen bond acceptor [19,31,32] and the affinity to protons increases with the number of substitutions [33]. With the exception of mannitol [34], which is a hydrogen bond donor and is protein resis- tant, this statement is well-accepted among the surface science community. Like GMA, amines have been widely used as block copolymer constituents in various applications [35–38], however, their use as a surface grafting material has not been given significant attention. 0376-7388/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2011.10.048