Properties of Ionic Liquid Confined in Porous Silica Matrix

Abstract

Porous silica matrices of different pore sizes with confined ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) [BMIM] [PF(6)] were prepared by sol-gel technique using a tetraethyl orthosilicate (TEOS) precursor with an aim to study the changes in physico-chemical properties of ionic liquid on confinement. It is found that on confinement 1) melting point decreases, 2) fluorescence spectra shows a red shift and 3) the vibrational bands are affected particularly those of imadazolium ring, which interacts more with the walls of the silica matrix. Preliminary theoretical calculations suggest that SiO(2) matrix interact more with the heterocyclic group of [BMIM] cation than the tail alkyl chain end group resulting in significant changes in the aromatic vibrations.

Effect of Ultrasonic Irradiation on Preparation and Properties of Ionogels

“…In our earlier experimental and theoretical studies on [BMIM][PF 6 ], we found that the cation ring gets weakly attached to the silica gel surface oxygen leading to changes in melting point, fluorescence, and vibrational bands [25]. It may be noted that all the studies listed above including our study [18][19][20][21][22][23][24][25] were on ILs with small anions. More recently, we have studied the IL with large anion size [BMIM][OcSO 4 ] and have proposed a phenomenological model to qualitatively account for the anion size dependence of melting point depression [14].…”

“…Most studies of ILs in confined geometry are focused on the imidazolium-based cations [19][20][21][22][23][24]. In our earlier experimental and theoretical studies on [BMIM][PF 6 ], we found that the cation ring gets weakly attached to the silica gel surface oxygen leading to changes in melting point, fluorescence, and vibrational bands [25]. It may be noted that all the studies listed above including our study [18][19][20][21][22][23][24][25] were on ILs with small anions.…”

Synthesis, characterization and the effect of temperature on different physicochemical properties of protic ionic liquids

“…As reaction media, the application of ILs for a wide variety of synthetic processes is an area of intensive research. Apart from these important applications, recently, ILs in confined geometry 14,15 attracted attention along with synthesis 16 , as reaction media 17 and effect of salts on IL 18 . ILs are also being used in variety of applications viz.…”

Enhancing the Thermal Stability of Ionogels: Synthesis and Properties of Triple Ionic Liquid/Halloysite/MCC Ionogels

“…Moreover, for the IL/Hal/MCC-4 composite, lower characteristic phase-transition temperatures were observed compared to those for the composites without polymer ( Table 3 ). It should be noted that the confinement effect is caused by the strong interaction of the ionic liquid with the inner surface of halloysite nanotubes [ 6 , 26 , 27 , 28 ].…”