Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes

Abstract

Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.

Electroresponsive structuring and friction of a non-halogenated ionic liquid in a polar solvent: effect of concentration

“…11 This IL was chosen due to its excellent lubrication and electro-responsive properties. 6,10,11,17,26 Prior to all measurements the pure [P 6,6,6,14 ][BMB] was baked under vacuum at 60 1C for approximately 72 h to remove traces of solvents and water. The solvents, PC (anhydrous, 99.7%, Sigma Aldrich) and 1,2-propylene-d 6 carbonate (d-PC; 99.5 atom % D, Qmx Laboratories Ltd), were used as received.…”

The Effect of Phenyl Substitutions on Microstructures and Dynamics of Tetraalkylphosphonium Bis(trifluoro‐ methylsulfonyl)imide Ionic Liquids

“…The tetraalkylphosphonium orthoborate ILs exhibit outstanding friction reducing and anti‐wear performance in tribological contacts with a wide variety of solid materials, and thus are attractive as alternative high‐performance lubricants and lubricant additives in tribology . The functional performance of ILs in tribological applications is rationalized by distinct ion structures of tetraalkylphosphonium cations and their preferential associations with anions and molecular solvents in IL matrices . It has been well demonstrated from experimental and computational perspectives that mesoscopic liquid organizations of trihexyltetradecylphosphonium ([P 6,6,6,14 ]) ILs are dominated by three distinct landscapes at different length scales associated with short range adjacency correlations, positive‐negative charge alternations at intermediate range, and long‐ranged polarity ordering correlations .…”

TheENUFmethod—Ewald summation based onnonuniformfast Fourier transform: Implementation, parallelization, and application

“…[99,100,102] Compared with traditional molten salts, like sodium chloride, one fascinating feature of ILs is that they exhibit distinct heterogeneous microstructures and dynamics spanning multiple length and time scales in bulk region and in confined environments. [99,[101][102][103][104][105][106] Both experimental and computational characterizations revealed that mesoscopic liquid organization of ILs is characterized by either sponge-like interpenetrating polar and apolar networks or segregated polar (apolar) domains within apolar (polar) framework depending on the relative ratios of polar groups over apolar moieties in ion species. [101,104,105,[107][108][109][110][111] Recent atomistic simulations of ILs demonstrated that both simulation size and simulation time do matter to get reliable collective structural and dynamical quantities of ions in IL matrices.…”

“…[99,[101][102][103][104][105][106] Both experimental and computational characterizations revealed that mesoscopic liquid organization of ILs is characterized by either sponge-like interpenetrating polar and apolar networks or segregated polar (apolar) domains within apolar (polar) framework depending on the relative ratios of polar groups over apolar moieties in ion species. [101,104,105,[107][108][109][110][111] Recent atomistic simulations of ILs demonstrated that both simulation size and simulation time do matter to get reliable collective structural and dynamical quantities of ions in IL matrices. [112] As simulations of ILs should be performed over long time scales due to sluggish dynamics of ion species in heterogeneous IL matrices, it imposes severe fundamental challenges for atomistic simulations to accurately predict dynamics and transport properties of ILs.…”