NMR relaxometric probing of ionic liquid dynamics and diffusion under mesoscopic confinement within bacterial cellulose ionogels

Abstract

Bacterial cellulose ionogels (BCIGs) represent a new class of material comprising a significant content of entrapped ionic liquid (IL) within a porous network formed from crystalline cellulose microfibrils. BCIGs suggest unique opportunities in separations, optically active materials, solid electrolytes, and drug delivery due to the fact that they can contain as much as 99% of an IL phase by weight, coupled with an inherent flexibility, high optical transparency, and the ability to control ionogel cross-sectional shape and size. To allow for the tailoring of BCIGs for a multitude of applications, it is necessary to better understand the underlying principles of the mesoscopic confinement within these ionogels. Toward this, we present a study of the structural, relaxation, and diffusional properties of the ILs, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([bmpy][Tf2N]), using 1H and 19F NMR T1 relaxation times, rotational correlation times, and diffusion ordered spectroscopy (DOSY) diffusion coefficients, accompanied by molecular dynamics (MD) simulations. We observed that the cation methyl groups in both ILs were primary points of interaction with the cellulose chains and, while the pore size in cellulose is rather large, [emim]+ diffusion was slowed by ∼2-fold, whereas [Tf2N]− diffusion was unencumbered by incorporation in the ionogel. While MD simulations of [bmpy][Tf2N] confinement at the interface showed a diffusion coefficient decrease roughly 3-fold compared to the bulk liquid, DOSY measurements did not reveal any significant changes in diffusion. This suggests that the [bmpy][Tf2N] alkyl chains dominate diffusion through formation of apolar domains. This is in contrast to [emim][Tf2N] where delocalized charge appears to preclude apolar domain formation, allowing interfacial effects to be manifested at a longer range in [emim][Tf2N].

Memristors With Controllable Data Volatility by Loading Metal Ion-Added Ionic Liquids

“…The peak positions of the Cu 2p 3/2 spectra in both IL/Cu and IL/SiO 2 are close to those in Cu(NO 3 ) 2 (935.51 eV) and CuSO 4 (936.00 eV) (Moretti and Beck, 2019). According to the previous reports, electrons delocalize within the S-N-S structure in Tf 2 N anion (Forsyth et al, 2002;Hapiot and Lagrost, 2008;Smith et al, 2018). Additionally, because oxygen is more electronegative than nitrogen and sulfur, it is expected that the electrons of Cu in the IL are shared by S, N, and O in Tf 2 N anion.…”

Low-Frequency Spectra of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Poly(ethylene glycol) by Femtosecond Raman-Induced Kerr Effect Spectroscopy

“…IL gels allow easy shape forming while keeping some physicochemical properties of ILs which expands the potential of application usages of IL. It is thus important to understand the relationship between physical properties and microscopic information, including structure, intermolecular interactions, and molecular dynamics to control the properties of IL/polymer mixtures. − Concerning IL/polymer systems, dynamics in IL mixtures with nonionic surfactants, such as Triton X-100 and poly­(oxyethylene glycol) ethers, were also investigated using time-resolved fluorescence spectroscopy. , …”

Combined Small-Angle Neutron Scattering, Diffusion NMR, and Molecular Dynamics Study of a Eutectogel: Illuminating the Dynamical Behavior of Glyceline Confined in Bacterial Cellulose Gels

“…The results indicate that the cellulose microfibrils in these samples are loosely entangled, forming a sparsely packed network. This suggests that the vast majority of the solvent is contained by large micropores within the cellulosic structure, implying mesoscopic confinement within bacterial cellulose gels, as appears to be the case for [emim]­[Tf 2 N] studied previously …”

“…In the current work, we introduce a new class of eutectogel inspired by our previous work with bacterial cellulose ionogels (BCIGs). Specifically, we incorporate the DES glyceline within a bacterial cellulose host to generate a novel type of eutectogel we subsequently denote a glyceline bacterial cellulose eutectogel (Gly-BCEG). − The structure of the bacterial cellulose was examined through the methods of X-ray diffraction (XRD) and small-angle neutron scattering (SANS) to ascertain changes induced by glyceline to the cellulose crystallinity and entanglement. Diffusion ordered spectroscopy (DOSY) was utilized to study the diffusive properties of glyceline within the eutectogel.…”