A new application of ionic liquids: hydrophobic properties of tetraalkylammonium-based poly(ionic liquid)s

The potential of using poly(ionic liquid)s as a new family of hydrorepellent materials has been explored. Free-radical polymerization of a series of ionic liquids based on the polymerizable cation [2-(methacryloyloxy) ethyl] trimethylammonium and on the hydrophobic anions bis(trifluoromethylsulfonyl) imide, nonafluoro-1-butanesulfonate and dodecylbenzenesulfonate led to the corresponding poly(ionic liquid) s that were characterized by TGA and DSC analysis, SEM, MALDI-TOF and XPS spectroscopy. Contact angle investigations show that the nature of the surface of the poly(ionic liquid) s based on the nonafluoro-1-butanesulfonate and dodecylbenzenesulfonate anions are featured by remarkable hydrophobic properties with advancing contact angles (theta(adv)) lying in the range 113-118 degrees, while to the polymer poly[ 2-(methacryloyloxy) ethyl] trimethylammonium bis(trifluoromethylsulfonyl) imide is associated poor hydrorepellent activity (theta(adv)=76 degrees). The tensiometric measurements also experience receding contact angles (theta(rec)) lying in the range 16-20 degrees and a consequent high hysteresis suggesting that, on the outermost layers of the polymers, very high and very low-energy surface portions are present.