Abstract
Films of zwitterionic polymers are increasingly explored for conferring fouling resistance to materials. Yet, the structural diversity of polyzwitterions is rather limited so far, and clear structure-property relationships are missing. Therefore, we synthesized a series of new polyzwitterions combining ammonium and sulfate groups in their betaine moieties, so-called poly(sulfabetaine)s. Their chemical structures were varied systematically, the monomers carrying methacrylate, methacrylamide, or styrene moieties as polymerizable groups. High molar mass homopolymers were obtained by free radical polymerization. Although their solubilities in most solvents were very low, brine and lower fluorinated alcohols were effective solvents in most cases. A set of sulfabetaine copolymers containing about 1 mol % (based on the repeat units) of reactive benzophenone methacrylate was prepared, spin-coated onto solid substrates, and photo-cured. The resistance of these films against the nonspecific adsorption by two model proteins (bovine serum albumin—BSA, fibrinogen) was explored, and directly compared with a set of references. The various polyzwitterions reduced protein adsorption strongly compared to films of poly(n-butyl methacrylate) that were used as a negative control. The poly(sulfabetaine)s showed generally even somewhat higher anti-fouling activity than their poly(sulfobetaine) analogues, though detailed efficacies depended on the individual polymer–protein pairs. Best samples approach the excellent performance of a poly(oligo(ethylene oxide) methacrylate) reference.
Highlights
Polyzwitterions—or synonymous polybetaines—bear within their constitutional repeat unit (CRU) pairs of anionic and cationic groups
For selected examples, we explored their utility for low-fouling coatings, as initial studies on polymers P−1d and P−3d had indicated good resistance against the adsorption of proteins [12,52]
As described for monomers 1c, 1d, 3c, 3d, 6c, and 6d [50], the new monomers 2c, 2d, 4c, 4d, 5c, and 5d were prepared by reaction of the respective tertiary amine functionalized methacrylates with cyclic sulfate diesters in acetonitrile, namely with ethylene sulfate or propylene sulfate
Summary
Polyzwitterions—or synonymous polybetaines—bear within their constitutional repeat unit (CRU) pairs of anionic and cationic groups They are characterized by a high density of ions attached to the polymer chain and strong electrostatic intra- and interpolymer interactions may occur, the net charge of polyzwitterions is inherently zero under normal conditions. Polyzwitterions represent a special subclass of polyampholytes featuring very particular properties, including high polarity (and often high hydrophilicity), anti-polyelectrolyte behavior and stimuli-responsiveness [1,2,3] By virtue of this exceptional property profile, they have increasingly attracted interest due to their great potential for diverse applications, such as biocompatibilization, cryo preservation, lubrication, smart self-assembly, and low-fouling surfaces in aqueous environments [4,5,6,7,8,9,10,11,12,13]. Polymers 2019, 11, 1014 cryo preservation, preservation, lubrication, lubrication, smart smart self-assembly, self-assembly, and and low-fouling low-fouling surfaces surfaces in in aqueous aqueous cryo environments[4,5,6,7,8,9,10,11,12,13]. [4,5,6,7,8,9,10,11,12,13]. environments Compared
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