@article{KocSchardtNolteetal.2020,
  author    = {Koc, Julian and Schardt, Lisa and Nolte, Kim and Beyer, Cindy and Eckhard, Till and Schwiderowski, Philipp and Clarke, Jessica L. and Finlay, John A. and Clare, Anthony S. and Muhler, Martin and Laschewsky, Andr{\´e} and Rosenhahn, Axel},
  title     = {Effect of dipole orientation in mixed, charge-equilibrated self-assembled monolayers on protein adsorption and marine biofouling},
  series = {ACS applied materials \& interfaces},
  volume    = {12},
  journal   = {ACS applied materials \& interfaces},
  number    = {45},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/acsami.0c11580},
  pages     = {50953 -- 50961},
  year      = {2020},
  abstract  = {While zwitterionic interfaces are known for their excellent low-fouling properties, the underlying molecular principles are still under debate. In particular, the role of the zwitterion orientation at the interface has been discussed recently. For elucidation of the effect of this parameter, self-assembled monolayers (SAMs) on gold were prepared from stoichiometric mixtures of oppositely charged alkyl thiols bearing either a quaternary ammonium or a carboxylate moiety. The alkyl chain length of the cationic component (11-mercaptoundecyl)-N,N,N-trimethylammonium, which controls the distance of the positively charged end group from the substrate's surface, was kept constant. In contrast, the anionic component and, correspondingly, the distance of the negatively charged carboxylate groups from the surface was varied by changing the alkyl chain length in the thiol molecules from 7 (8-mercaptooctanoic acid) to 11 (12-mercaptododecanoic acid) to 15 (16-mercaptohexadecanoic acid). In this way, the charge neutrality of the coating was maintained, but the charged groups exposed at the interface to water were varied, and thus, the orientation of the dipoles in the SAMs was altered. In model biofouling studies, protein adsorption, diatom accumulation, and the settlement of zoospores were all affected by the altered charge distribution. This demonstrates the importance of the dipole orientation in mixed-charged SAMs for their inertness to nonspecific protein adsorption and the accumulation of marine organisms. Overall, biofouling was lowest when both the anionic and the cationic groups were placed at the same distance from the substrate's surface.},
  language  = {en}
}
@article{KocSchoenemannArnuthalingametal.2019,
  author    = {Koc, Julian and Sch{\"o}nemann, Eric and Arnuthalingam, Ajitha and Clarke, Jessica L. and Finlay, John A. and Clare, Anthony S. and Laschewsky, Andre and Rosenhahn, Axel},
  title     = {Low-fouling thin hydrogel coatings made of photo-cross-linked polyzwitterions},
  series = {Langmuir},
  volume    = {35},
  journal   = {Langmuir},
  number    = {5},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0743-7463},
  doi       = {10.1021/acs.langmuir.8b02799},
  pages     = {1552 -- 1562},
  year      = {2019},
  abstract  = {Although zwitterionic chemistries are among the most promising materials for producing nonfouling surfaces, their structural diversity has been low until now. Here, we compare the in vitro fouling behavior of a set of four systematically varied sulfa-/sulfobetaine-containing zwitterionic hydrogel coatings against a series of proteins and nonmotile as well as motile marine organisms as model foulers. The coatings are prepared by simultaneous photoinduced cross-linking and surface anchoring to elucidate the effect of the molecular structure of the zwitterionic moieties on their antifouling activity. Analogously prepared coatings of poly(butyl methacrylate) and poly(oligoethylene glycol methacrylate) serve as references. Photoreactive polymers are synthesized by the statistical copolymerization of sulfobetaine or sulfabetaine methacrylates and methacrylamides with a benzophenone derivative of 2-hydroxyethyl methacrylate and are applied as a thin film coating. While keeping the density of the zwitterionic and cross-linker groups constant, the molecular structure of the zwitterionic side chains is varied systematically, as is the arrangement of the ion pairs in the side chain by changing the classical linear geometry to a novel Y-shaped geometry. All of the polyzwitterions strongly reduce fouling compared to poly(butyl methacrylate). Overall, the sulfabetaine polyzwitterion coatings studied matches the high antifouling effectiveness of oligo(ethylene glycol)-based ones used as a control. Nevertheless, performances varied individually for a given pair of polymer and fouler. The case of the polysulfobetaines exemplifies that minor chemical changes in the polymer structure affect the antifouling performance markedly. Accordingly, the antifouling performance of such polymers cannot be correlated simply to the type of zwitterion used (which could be generally ranked as better performing or poorer performing) but is a result of the polymer's precise chemical structure. Our findings underline the need to enlarge the existing structural diversity of polyzwitterions for antifouling purposes to optimize the potential of their chemical structure.},
  language  = {en}
}