The effect of media to reduce irradiation dose in crosslinking of self-assembled molecular layers

Abstract

The present study aims to investigate the possibility of reducing the absorbed dose required to prepare a polymer nanocoating for surface functionalization by modifying the irradiation medium. We have studied the crosslinking of elaidic acid (EA), an unsaturated trans fatty acid, on oxidised copper by gamma irradiation. Three different irradiation media were compared: water purged with N2, water purged with N2O, and air purged with N2. Contact angle measurements were used to determine the hydrophobicity of the surface. The coatings were investigated by electrochemical measurements: The degree of crosslinking was indirectly determined by polarization measurements, while the behaviour of the coatings was studied by electrochemical impedance spectroscopy. The results showed that crosslinking can be achieved in all media studied. The highest dose of 110 kGy is required when irradiation is performed in oxygen-free air, while much lower doses of 40 kGy are required when irradiation is performed in water that has been purged with both gases used. The highest degree of crosslinking is achieved when irradiation is performed in air, while the degree of crosslinking when irradiated in water is highly dependent on the gas used. If N2O is used, the degree of crosslinking is significantly higher. The surface of the coatings is more hydrophobic when polymer coatings are present on the surface, regardless of the irradiation medium.