Yogendra Lal Verma

Thermal, electrical and structural studies on ionic liquid confined in ordered mesoporous MCM-41

In the present study, immobilization of different amounts of ionic liquid (IL) 1-ethyl-3-methyl imidazolium tetrafluoroborate [EMIM][BF4] into the pores of ordered mesoporous MCM-41 (Mobil Composition of Matter no. 41) has been accomplished successfully. Differential scanning calorimetry (DSC) and dielectric spectroscopy results indicate the presence of surface adsorbed IL besides, IL confined in pores. The IL adsorbed on the surface of MCM-41 has been removed after washing. DSC and dielectric spectroscopy results and scanning electron microscopy (SEM) confirm the removal of the surface adsorbed IL. Glass transition temperature (Tg) and thermal stability have been found to change as compared to the bulk IL in confinement. An FTIR study shows that the vibrational bands related to the ring of the IL cation shift upon confinement due to the interaction between oxygen of the silica pore wall surface and C–H of the cation ring. Anion [BF4]− also interacts with the pore wall as confirmed experimentally and theoretically. Fluorescence spectra of IL show the blue shift upon incorporation into the ordered mesoporous MCM-41.

Changes in dynamical behavior of ionic liquid in silica nano-pores

Dielectric relaxation measurement has been carried out on an ionic liquid (1-butyl-3-methyl imidazolium hexafluorophosphate, [BMIM][PF6]) confined in nano-porous silica matrix. Two dielectric relaxation peaks have been observed in the confined ionic liquid (IL) while there is only one relaxation peak for bulk IL. Confinement results in layering of some IL molecules near the pore wall while other molecules, less affected by pore wall interaction, remain in the central core. The two relaxation peaks are assigned to the different dynamical behaviors of the central core and layered IL molecules.

Effect of ultrasonic irradiation on preparation and properties of ionogels

Silica-gel matrices containing ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate viz. ionogels have been synthesized using one-pot nonhydrolytic sol-gel method and taking tetraethyl orthosilicate (TEOS) as starting precursor. Effect of ultrasonic irradiation on pore parameters of ionogels and vibrational properties of the IL upon confinement in the porous matrix has been investigated. The synthesized gels have been characterized by BET, DSC, TGA, and FTIR. BET analysis shows some changes in the pore parameters due to ultrasonic irradiation. DSC results indicate shift in glass transition temperature upon confinement of the IL. The FTIR spectra show changes in vibrational bands on confinement, particularly, the bands related to the imidazolium ring, aliphatic chain and anion PF6 - of the IL are found to shift upon confinement in porous silica matrix obtained due to ultrasonic irradiation. Ultrasonic irradiation has been found to affect the gelation dynamics and kinetics and pore parameters.

Ionic liquid template assisted synthesis of porous nano-silica nails

Our planned strategy to obtain porous materials was to synthesize porous silica at a fast gelation rate which can be attained by using non-hydrolytic sol–gel route with high ionic liquid (IL)-loading. Then the silica might get drawn into a tubular spring-like structure that would cage the ionic liquid within its fold and some ionic liquid might get into the pores of the silica spring. To test this strategy, we used a mixture of tetra methyl ortho-silane and ionic liquid in such a ratio that the resulting product, SiO2 : IL, has a content of IL as high as 85–92 wt%. Interestingly, the experimental results described in this paper have proved the validity of our strategy to obtain “porous” nano-silica particles (sometimes, “porous nail” structures also resulted).

Role of ionic liquid [BMIMPF6] in modifying the crystallization kinetics behavior of the polymer electrolyte PEO-LiClO4

We report on the modification in crystallization kinetics behavior of PEO + 10 wt% LiClO4 polymer electrolyte by the addition of an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6). Three techniques have been used for studying crystallization kinetics, viz., (i) isothermal crystallization technique using DSC, (ii) non-isothermal crystallization technique using DSC, and (iii) by monitoring the growth of spherulites with time in the polymer electrolyte films using a polarizing optical microscope (POM). Results from all the three techniques show that the presence of ionic liquid BMIMPF6 suppresses the crystallization rate due to its plasticization effect. Isothermal crystallization data was well described by the Avrami equation, and Avrami exponent n lies in the range of 1 to 2, which signifies 2D crystal growth geometry occurring in these polymer electrolytes under the investigated temperature range. However, the Avrami crystallization rate constant ‘K’ increases exponentially with crystallization temperature and ionic liquid content as well. However, the non-isothermal crystallization kinetics of these polymer electrolytes is discussed in terms of three different models (Jeziornys, Ozawas and Mos method), and it is found that Mos method better explains the non-isothermal crystallization data. In addition, crystalline morphology and spherulite growth were studied by POM, which shows the suppression in crystallization in the presence of ionic liquid, as confirmed by spherulite growth rate (Gs) analysis.