Chitosan coatings with modulated surface roughness for the inhibition of marine macrofouling

Surface roughness is known to influence biofouling in marine environments. Different from the conventional antifouling coatings based on hydrophobic polymeric materials such as epoxy and polydimethylsiloxane (PDMS), in this study, naturally occurring compound benzophenone-3 (BP-3) modified chitosan (CS) biopolymer coatings with varied surface roughness were prepared and studied for their antifouling effect for the first time. By regulating the competitive reactions between the reactants, different condensation products can be obtained which result in varied root mean square (RMS) roughness of CS-BP-3 coatings from 7.6 nm to 270.0 nm. It is found that the reaction time influences more than the reaction temperature while defining the surface roughness of CS-BP-3 coatings. Specifically, the coatings of CS-BP-3 prepared from a 2-h reaction led to RMS roughness between 7.6 and 55.18 nm, whereas after 12-h reaction roughness between 82.6 and 270.0 nm were measured. Subsequent antifouling experiments indicate that rougher coatings have a more pronounced effect of preventing the settlement of plantigrade mollusk mimicking the lotus effect. This work demonstrates that bio-inspired materials can be designed to achieve desired functions for practical applications.