Because most "low fouling" polymers resisting bacterial attachment are hydrophilic, they are usually also significantly swollen. Swelling leads to purely physical dilution of interaction and weakens attachment; however, these nonspecific contributions are usually not separated from the specific effect of polymer chemistry. Taking advantage of the fact that chemistry and swelling of hydrogels may be independently varied through the fraction of a cross-linker, the roles of chemistry and physical dilution (swelling) in bacterial attachment are analyzed for selected hydrogels. Using as a quantitative indicator the rate of bacterial deposition in a parallel plate setup under defined flow conditions, the observed correlation of deposition rate with swelling provides a straightforward comparison of gels with different chemistries that can factor out the effect of swelling. In particular, it is found that chemistry appears to contribute similarly to bacterial deposition on hydrogels prepared from acrylamide and a zwitterioninic monomer 2-(methacryloyloxy)ethyl) dimethyl-(3-sulfopropyl) ammonium hydroxide so that the observed differences may be related to swelling only. In contrast, these gels were inferior to PEG-based hydrogels, even when swelling of the latter was lower, indicating a greater contribution of PEG chemistry to reduced bacterial deposition. This demonstrates that swelling must be accounted for when comparing different biofouling-resistant materials. Chemical and physical principles may be combined in hydrogel coatings to develop efficient antibiofouling surfaces.
Novel solid polymeric catalysts consisting of polymer chains have been synthesized to facilitate cellulose dissolution and catalyze its hydrolysis. Poly(styrene sulfonic acid) (PSSA) polymer chains have been grown from the substrate surface and used to catalyze biomass hydrolysis. Neighboring poly(vinyl imidazolium chloride) ionic liquid (PIL) polymer chains, also grown from the substrate surface, help solubilize lignocellulosic biomass and enhance the catalytic activity of the PSSA chains. The PSSA chains were synthesized via surface initiated atom-transfer radical polymerization (ATRP) whereas the adjacent PIL chains were synthesized via UV-initiated free radical polymerization. These novel polymeric solid acid catalysts demonstrate over 97% and 32% total reducing sugar (TRS) yields from cellulose hydrolysis in [EMIM]Cl and aqueous solutions respectively. The dual ATRP and UV-initiated polymerization schemes allow independent variation of the relative ratio of the two nanostructures as well as the chain length and density. This permits optimization of the catalytic activity for cellulose hydrolysis reaction. These catalysts are stable and maintain high catalytic activity after repeated runs.
A series of hydrogels based on poly(ethylenglycol) methyl ether methacrylate (PEGMEMA) is synthesized using macromonomers of three different molecular weights, in combination with varied degrees of chemical crosslinking. The effects of PEGMEMA, initiator, and crosslinker concentrations on gel yield and swelling properties are studied. In addition, the chemical structure of the gels is characterized by FTIR and solid‐state NMR spectra. The swelling and rheological behaviors of hydrogels as well as protein partitioning into the gels are discussed in terms of the network mesh size. Low protein sorption and bacteria deposition tendencies indicate that PEGMEMA‐based hydrogels could be highly beneficial for uses as fouling‐resistant materials, for instance, as protective coatings for desalination membranes.
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