Spacer Effects in Sulfo‐ and Sulfabetaine Polymers on Their Resistance against Proteins and Pathogenic Bacteria

The resistance of zwitterionic polymer coatings against the adsorption of proteins and the attachment of pathogenic bacteria is influenced by the precise molecular architecture of the polymers. Two until now rarely studied molecular variables in this context are side chain spacer groups separating the zwitterionic moieties from the polymer backbone and spacer groups separating the cationic and anionic groups within the zwitterionic moiety. Therefore, a set of six poly(sulfobetaine)s and poly(sulfabetaine)s is prepared, in which these spacer groups are systematically varied, incorporating ethylene, propylene, and undecylene side chain spacers, as well as ethylene, propylene, and butylene inter‐charge spacers, and their effects on the antifouling behavior are explored. Hence, the corresponding zwitterionic methacrylates are copolymerized with a photo‐reactive methacrylate bearing a benzophenone moiety. All zwitterionic coatings reveal hydrophilic properties when immersed in water and those with relatively short spacers show effective suppression of non‐specific protein adsorption. Polysulfobetaines outperform the polysulfabetaine ones in terms of resistance against adhesion of bacteria. The overall best fouling protection is observed for the polysulfobetaine bearing a propylene side chain spacer, which coincides with their relatively highest water solubility. The results corroborate previous findings that even apparently minor molecular changes of polyzwitterions can strongly affect their antifouling performance. Hydrophilic sulfobetaine‐based polymers with relatively short inter‐charges and side‐chain spacers outperform analogous sulfabetaines in terms of bacterial fouling resistance. An extended undecyl side‐chain spacer results in increased hydrophobicity in the air but retains rapid reorientation and hydrophilicity underwater, whereby the resistance to proteins and bacterial accumulation is partially compromised.