In this study, surface modification of both organic and inorganic substrates (in terms of cellulose and silica nanoparticles, respectively) has been explored using surface-initiated atom transfer radical polymerisation (ATRP). The desire to modify bio-based materials to fit into new application areas and the need for bio-based materials with improved material properties is steadily increasing due to environmental concern. Superhydrophobic and self-cleaning cellulose surfaces were fabricated by combining ATRP with post-functionalisation. Glycidyl methacrylate was grafted from filter paper, and the epoxide groups were used as reactive handles to create a branched “graft-on-graft” architecture. Post-functionalisation of this architecture with perfluorinated chains or alkyl chains resulted in the formation of superhydrophobic surfaces. Grafting of N-isopropylacrylamide (NIPAAm) from filter paper yielded cellulose surfaces capable of switching the wettability, from hydrophilic to hydrophobic, in response to changes in temperature. The wettability of cellulose surfaces grafted with poly(4-vinylpyridine) (P4VP) could be adjusted from hydrophilic to hydrophobic by changing pH. Furthermore, cellulose surfaces responding to changes in both pH and temperature were obtained via grafting of block copolymers of PNIPAAm and P4VP. The use of inorganic nano-particles in composites has attracted considerable academic and industrial interest due to their excellent mechanical and thermal properties. Styrene was grafted from the surface of silica nanoparticles using ATRP. The resulting organic-inorganic hybrid materials did not aggregate to the same extent as the un-modified silica particles. The polystyrene-modified silica particles were used for the fabrication of honeycomb membranes. It was evident that the pore sizes and the number of porous layers could be tuned by varying the conditions used for film casting. To broaden the range of polymers available for film casting into honeycomb membranes, a block copolymer of polystyrene and poly(methyl methacrylate) was grafted from silica nanoparticles. Polymer-blends of polystyrene-modified particles and poly(9,9´-dihexylfluorene) (PDHF) were also used as an alternative to incorporate functionality into honeycomb membranes. / QC 20100901

The primary aim of this work is to explore the potential applications of isoporous block copolymer membranes. Block copolymers (BCPs) have demonstrated their versatility in the formation of isoporous membranes. However, application spectrum of these isoporous membranes can be further broadened by exploring the technical aspects, such as desired surface chemistry, well-defined pore size, appropriate pore density, stimuli responsive behavior, and by imparting desired functionalities through chemical modifications. We believe, by exploring these possibilities, isoporous membranes hold tremendous potential as high performance next generation separation membranes. Motivated by these attractive prospects we systematically investigated novel routes for modification of isoporous membranes and their implications on properties and performance of the membranes for various applications. In this work, polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) has been selected to fabricate isoporous membranes using non-solvent induced phase separation (NIPS). We selected PS-b-P4VP since its well-defined isoporous morphology is studied in detail and it is extensively characterized. In order to further widen the application bandwidth of BCP membranes, it is desirable to integrate different functionalities in the BCP architecture through a straightforward approach like post-membrane-modification or fabrication of composite membranes to impart anticipated functionalities. The most critical challenge in this approach is to retain the well-defined nanoporous morphology of BCP membranes. We focused on exploring new routes for chemical functionalization of isoporous PS-b-P4VP membranes via various in-situ and post-membrane fabrication approaches. To date, most of the work reported in the literature on PS-b-P4VP presented different routes to fabricate isoporous membranes and their conventional performance in liquid separations. Few efforts have been dedicated to alter the chemistry of PS-b-P4VP membranes by tuning the reactivity of the chemically active P4VP block or the surface chemistry to enhance the membrane performance for desired applications. During the Ph.D. study, we primarily focused on: (i) post modification approach, (ii) surface modification and (iii) in-situ membrane modification approach for fabrication of the mixed-matrix nanoporous membranes without altering the isoporous morphology of the membrane. The membranes fabricated using the mentioned above routes were tested for different applications like stimuli-responsive separations, self-cleaning membranes, protein separations and high-performance humidity sensors.