Polyion multilayers with precise surface charge control for antifouling.

We report on a molecular fabrication approach to precisely control surface ζ potentials of polymeric thin layers constructed by electrostatic layer-by-layer (LbL) assembly methods. The protocol established allows us to achieve surface isoelectric points (IEP) in the pH range of 6-10. Poly(acrylic acid) (PAA, a weak polyanion) and poly(diallyldimethylammonium chloride) (PDADMAC, a strong polycation) were chosen to build up the bulk films. The weak polycation polyethylenimine (PEI) was applied as a top layer. A unique feature of this approach is that the chemical composition of the top layer is not affected by the manipulation of the ζ potential of the films. Surface charge tuning is achieved by controlling the degree of ionization of the weak polyelectrolytes at various pH values and subsequent manipulation of the amount of polyelectrolyte deposited in the penultimate and last layers, respectively. Following assembly and characterization, the films were used as candidates for antifouling surfaces. The fouling behavior of barnacle cyprids and bacteria on the LbL films with similar hydrophilicity and roughness but different surface charge densities were studied. We found that more cyprids of Amphibalanus amphitrite settled on the negatively charged LbL film compared to the neutral or positively charged LbL film. In bacterial adhesion tests employing Pseudomonas, Escherichia coli, and Staphylococcus aureus, more bacteria were observed on the positively charged LbL film compared with the neutral and negatively charged LbL films, possibly as a result of the negative potential of the bacterial cell wall. The procedures proposed allow one to adjust surface isoelectric points of LbL architectures to achieve optimal antifouling performance of a given material taking into account specific pH values of the environment and the character of the fouler.

Sulfobetaine-based polymer brushes in marine environment: is there an effect of the polymerizable group on the antifouling performance?

Three different zwitterionic polymer brush coatings for marine biofouling control were prepared by surface-initiated atom transfer radical polymerization (ATRP) of sulfobetaine-based monomers including methacrylamide (SBMAm), vinylbenzene (SBVB) and vinylimidazolium (SBVI). None of these brush systems have been assessed regarding marine antifouling performance. Antifouling tests performed indicate that surfaces featuring these three brush systems substantially reduce the adhesion of the marine microalgae, Amphora coffeaeformis, and the settlement of cyprid larvae of the barnacle, Amphibalanus amphitrite, in a similar way, displaying comparable performance. Thus, it appears that the chemical structure of the polymerizable group has no substantial influence on marine antifouling performance.

New records of the genus Agelas Duchassaing & Michelotti, 1864 (Porifera, Agelasida) off the Amazon River mouth, Brazil, Southwestern Atlantic / Novos registros do gênero Agelas Duchassaing & Michelotti, 1864 (Porifera, Agelasida) ao largo da desembocadura do Rio Amazonas, Brasil, Atlântico Sudoeste

This work provides new information on agelasid sponges found on the continental shelf off northern Brazil. Agelas sceptrum (Lamarck, 1815) and Agelas wiedenmayeri Alcolado, 1984 have their first record for the Brazilian coast. Agelas dispar Duchassaing & Michelotti, 1864 and Agelas schmidti Wilson, 1902, previously recorded from Brazil, are cited for the first time off the mouth of the Amazon River.

Este trabalho fornece novas informações sobre esponjas agelasidas encontradas na costa norte da plataforma continental brasileira. Agelas sceptrum (Lamarck, 1815) e Agelas wiedenmayeri Alcolado, 1984 têm seu primeiro registro para a costa brasileira. Agelas dispar Duchassaing & Michelotti, 1864 e Agelas schmidti Wilson, 1902, registradas anteriormente na costa brasileira, são citadas pela primeira vez ao largo da desembocadura do Rio Amazonas.