Formation, structure and antibacterial activities of silazane networks grafted with poly(ethylene glycol) branches

The aim of this investigation was to develop coating materials based on poly(ethylene glycol) (PEG) covalently grafted onto silazane polymers for marine antifouling applications. The optimum conditions for grafting PEG were defined to have a high selectivity toward olefin hydrosilylation. Thick crack-free films were obtained by curing at room temperature of the PEG grafted silazane precursors. The solidification process has been investigated by FTIR spectroscopy, 29Si NMR in the solid state, thermogravimetric analysis (TGA) as well as elemental analysis. The main reactions that occur during curing are hydrolysis-condensation reactions of alkoxysilane, Si-H and Si-N functionalities. The PEG-graft-PSZ coatings exhibit excellent repellency against gram-negative Neisseria sp. and gram-positive Clostridium sp. in comparison with the pristine polysilazane surface. The anti-adhesion performance of the coatings depends on the grafting density and the chain length of PEG. The shortest PEG(350g/mol)-graft-PSZ with the highest graft density was found to have the best anti-adhesion performance. As the density of grafted PEG(750g/mol) and PEG(2000g/mol) chains onto the PSZ surface is approximately equal, the relative effectiveness of these two types of PEG is controlled by the length of the PEG chain. The PEG(2000g/mol)-graft-PSZ coatings are more efficient than the PEG(750g/mol)-graft-PSZ coatings for the bacterial anti-adhesion.