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

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