| The synthesis and characterization of a series of novel hydrophobic room temperature ion liquids (RTILs) are reported along with their applications in a variety of different systems ranging from electrochemical cells to biphasic separations. The effect of alkyl chain length, anion composition, and the SiO2 surface charge density were examined in 1-alkyl-3-methylimidazolium cations (Cnmim, n = 4, 6, 8, 10, 12) at the RTIL/SiO2 interface using sum frequency vibrational spectroscopy (SFVS). These studies concluded that the orientation of the 1-alkyl-3-methylimidazolium cation was dictated largely by the length of the alkyl chain. As the alkyl chain length increased, the number of gauche defects in the chain decreased, and the imidazolium ring orientation becomes more perpendicular to the SiO2 surface. Changes in the surface charge density of the SiO2 also affected the orientation of the imidazolium ring. As the surface charge density became more negative the imidazolium ring oriented more parallel to the surface.;Additionally, the oxidation of hydrogen and reduction of oxygen were examined in two hydrophobic RTILs. The RTILs used in this study were C 12mim bis(perfluoroethylsulfonyl)imide (BETI) and 1-dodecylimidazolium (C12im) BETI. The water concentration in the system was examined in addition to effects due to cation composition. Under water-equilibrated conditions the C12imBETI was more efficient than C12mimBETI and exhibited greater thermal stability in the electrochemical cell. Under ambient conditions the performance of the C12imBETI decreased and the performance of the C12mimBETI increased. This contradictory trend was attributed to different water structures within the RTILs.;Finally, the subclass of chiral RTILs was explored. The chiral RTILs were made by pairing the D or L-N-hexyl-alpha-methylbenzylammonium (C6mba) and the D or L-N-hexyl-N,N,-dimethyl-alpha-methylbenzylammonium (C611mba) cation with BMSI and BETI anions. The bulk properties of these RTILs were examined under both water-equilibrated and ambient conditions and were found to be independent of enantiomeric form. Their structure at an octadecyltrichlorosilane coated SiO2 surface was examined using counterpropagating second harmonic generation (SHG). It was found that the most hydrophobic RTIL, C611mbaBETI, exhibited the highest adsorption at this interface.;The studies presented here give new insight into how the ion composition of RTILs affects interfacial, bulk, and electrochemical properties. |
