Sandia’s Marine Hydrokinetic (MHK) Advanced Materials program has a new publication on the antifouling efficacy of zwiterionic coatings. These polymeric coatings contain no metal and have both positive and negative chemical charges as part of their molecular structure. The coating was investigated in response to finding environmentally friendly materials for MHK devices by the Sandia-UNM Advanced Materials Laboratory and North Dakota State University. The research was published in Biofouling: The Journal of Bioadhesion and Biofilm Research.

Structures of the zwitterionic coatings synthesized for this study.

Structures of the zwitterionic coatings synthesized for this study.

Abstract

Average adhesion values for reattached adult barnacles that were dislodged from the coating surfaces without incurring visible damage or breakage to baseplates. The ratios above each bar indicate the total number of barnacles removed without baseplate damage vs the number of barnacles that exhibited baseplate damage during force gage removal. Data points that share a letter are not statistically different from one another (ANOVA, α = 0.05).

Average adhesion values for reattached adult barnacles that were dislodged from the coating surfaces without incurring visible damage or breakage to baseplates. The ratios above each bar indicate the total number of barnacles removed without baseplate damage vs the number of barnacles that exhibited baseplate damage during force gage removal. Data points that share a letter are not statistically different from one another (ANOVA, α = 0.05).

A series of polysulfone and polyacrylate-based zwitterionic coatings were prepared on epoxy-primed aluminum substrata and characterized for their antifouling (AF) and fouling-release (FR) properties toward marine bacteria, microalgae and barnacles. The zwitterionic polymer coatings provided minimal resistance against bacterial biofilm retention and microalgal cell attachment, but facilitated good removal of attached microbial biomass by exposure to water-jet apparatus generated hydrodynamic shearing forces. Increasing the ion content of the coatings improved the AF properties, but required a stronger adhesive bond to the epoxy-primed aluminum substratum to prevent coating swelling and dissolution. Grafted poly(sulfobetaine) (gpSBMA), the most promising zwitterionic coating identified from microfouling evaluations, enabled the removal of four out of five barnacles reattached to its surface without incurring damage to their baseplates. This significant result indicated that gpSBMA relied predominately on its surface chemistry for its FR properties since it was very thin (~1–2 µm) relative to commercial coating standards (>200 µm).