The morphologies and dynamics of aggregates formed by surfactant molecules are known to influence strongly performance properties spanning biology, household cleaning, and soil cleanup. Molecular dynamics simulations were used to investigate the morphology and dynamics of a class of surfactants, the gemini or dimeric surfactants, that are of potential importance in several industrial applications. Simulation results show that these surfactants form structures and have dynamic properties that are drastically different from those of single-chain surfactants. At the same weight fraction, single-chain surfactants form spherical micelles whereas gemini surfactants, whose two head groups are coupled by a short hydrophobic spacer, form thread-like micelles. Simulations at different surfactant concentrations indicate the formation of various structures, suggesting an alternative explanation for the unexpected viscosity behavior of gemini surfactants.

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Layer-by-layer (LbL) assembly is a versatile platform for applying coatings and studying the properties of promising compounds for antifouling applications. Here, alginate-based LbL coatings were fabricated by alternating the deposition of alginic acid and chitosan or polyethylenimine to form multilayer coatings. Films were prepared with either odd or even bilayer numbers to investigate if the termination of the LbL coatings affects the physicochemical properties, resistance against the nonspecific adsorption (NSA) of proteins, and antifouling efficacy. The hydrophilic films, which were characterized using spectroscopic ellipsometry, water contact angle goniometry, ATR-FTIR spectroscopy, AFM, XPS, and SPR spectroscopy, revealed high swelling in water and strongly reduced the NSA of proteins compared to the hydrophobic reference. While the choice of the polycation was important for the protein resistance of the LbL coatings, the termination mattered less. The attachment of diatoms and settling of barnacle cypris larvae revealed good antifouling properties that were controlled by the termination and the charge density of the LbL films.

Combining high hydrophilicity with charge neutrality, polyzwitterions are intensely explored for their high biocompatibility and low-fouling properties. Recent reports indicated that in addition to charge neutrality, the zwitterion’s segmental dipole orientation is an important factor for interacting with the environment. Accordingly, a series of polysulfobetaines with a novel architecture was designed, in which the cationic and anionic groups of the zwitterionic moiety are placed at equal distances from the backbone. They were investigated by in vitro biofouling assays, covering proteins of different charges and model marine organisms. All polyzwitterion coatings reduced the fouling effectively compared to model polymer surfaces of poly­(butyl methacrylate), with a nearly equally good performance as the reference polybetaine poly­(3-(N-(2-(methacryloyloxy)­ethyl)-N,N-dimethylammonio)­propanesulfonate). The specific fouling resistance depended on the detailed chemical structure of the polyzwitterions. Still, while clearly affecting the performance, the precise dipole orientation of the sulfobetaine group in the polyzwitterions seems overall to be only of secondary importance for their antifouling behavior.

Whereas the structural diversity of zwitterions is a priori very high comprising a plethora of different anionic as well as cationic groups, [12] commonly used zwitterionic materials for low-fouling purposes belong to the three major families of carboxybetaine, sulfobetaine, and phosphatidylcholine containing polymers. [7,[12][13][14][15] Several studies have shown that the precise molecular structure of these polymers affects their inertness against fouling. Essential molecular parameters include not only the chemistry of both the anionic and the cationic groups, [16][17][18][19][20][21][22][23][24][25] but also the nature of the polymer backbone, [16,17,22,[26][27][28][29] the distance of the zwitterionic moieties from the backbone, [16,[30][31][32] the zwitterion's dipole orientation, [18,[33][34][35][36] and the length of the alkylene spacer between the ionic groups. [17,[37][38][39] For instance, in a set of otherwise identical polycarboxybetaines with varying inter-charge spacer, the adsorption of blood protein fibrinogen was lowest for two carbon atoms separating the ammonium and the carboxylate groups, increasing in the order 2 < 1 < 3 < 5. [40] Similarly, polycarboxybetaines with one and two carbon atoms separating the ammonium and the carboxylate groups were significantly more effective in reducing fouling by human blood