Construction of antifouling marine coatings via layer-by-layer assembly of chitosan and acid siloxane resin

Biofouling is the growth of plants, bacteria, and aquatic animals on manmade surfaces submerged in seawater. Recently, biofouling has caused a negative impact on the marine sector such as hull weight increases, low speed, and excessive fuel consumption, etc. Layer-by-layer (LBL) self-assembly of alternate charged polyelectrolytes on film with various numbers of layers provides an efficient method for putting antibacterial and anti-adhesive compounds on films. This antifouling coating LBL approach is a novel solution, which is based on the alternate deposition of oppositely charged polyelectrolytes. In this study, we assembled different number of layers on film comprised of chitosan (CHT) and acid siloxane resin (ASR) as a cationic and an anionic solution for LBL assembly using the dipping method. Then, the as-prepared polyelectrolyte multilayer (PEM) films were investigated by various techniques. FTIR analysis of CHT, ASR and assembled (CHT/ASR)2 film was carried out to confirm the functional groups responsible for their successful synthesis. SEM analysis was observed for each film in order to see the surface morphology, which showed a successful assembly of PEM films. AFM was used to see the topography of each as-prepared film; it was also observed that AFM results have agreement with SEM observations. The contact angle (CA) measurement depicted that the CA for PEM films increased with the increasing number of layers. The chemical bonding nature and composition of the PEM films were determined using XPS analysis. Marine diatom settlement and growth inhibition test was observed against Nitzschia closterium (NC) on each film for antifouling performance. It was observed that more algae cells were attached to the film surface of the (CHT/ASR)2, (CHT/ASR)4, (CHT/ASR)6 layer as compared with the (CHT/ASR)8 and (CHT/ASR)10 layers in NC diatom suspension. On the seventh day, the (CHT/ASR)10 layer film showed 0.0619 cell/105 number/mL of diatom cell attachment in the suspension, which is only 11% of the blank. This study provides new insights into the LBL approach for the development of CHT/ASR PEM films with desirable antifouling and environmentally friendly properties.