Cross-linking of antimicrobial polymers with hexamethylene diamine to prevent biofouling in marine applications

The design of antimicrobial polymers is a growing field, as they may replace conventional antimicrobial agents leading to plenty of advantages in marine applications. Polymers with active functional groups may act as carriers for antimicrobial agents. The antimicrobial polymers P(SSAmC16-co-GMAx) and P(VBCHAM-co-AAx) bearing quaternary ammonium compounds, either electrostatically bound (cetyltrimethylammonium 4-styrene sulfonate, SSAmC16) or covalently attached (vinyl benzyl dimethylhexadecylammonium chloride, VBCHAM), were prepared in the present work. The cross-linking agent hexamethylene diamine (HMDA) was used for the reaction between copolymers' reactive groups, epoxide groups of glycidyl methacrylate (GMA) or carboxylic groups of acrylic acid (AA), with the amine groups. Various blends of each reactive copolymer with hexamethylene diamine in different compositions were prepared and the cross-linking reaction was explored through solution casting after curing at room temperature (RT), 80 degrees C and 120 degrees C for 24 h in order to find the best conditions for the designing of a firm and strong coating. In a further step, specific blend combinations of the reactive antimicrobial copolymers combined with hexamethylene diamine were used to coat pre-weighed aquaculture nets which were cross-linked at 120 degrees C and used in laboratory accelerated conditions as well as in real conditions by immersion of the nets at an aquaculture unit in the Saronic Bay of Greece. The modified nets along with blank nets were tested in terms of antifouling efficacy for 35 days in accelerated conditions and 30 days in real conditions. The novel cross-linked antimicrobial coatings indicated high antifouling activity and high cleaning efficacy as the fouling microorganisms at the end of the test were easily removed from the coated net in contrast to the uncoated net after high pressure cleaning.

Automated summary

The study prepared antimicrobial polymers with quaternary ammonium compounds and coated them on aquaculture nets, showing high antifouling activity and cleaning efficacy. The modified nets performed well in preventing fouling microorganisms, which were easily removed after high pressure cleaning.