Phase Behaviors of Ionic Liquids Heating from Different Crystal Polymorphs toward the Same Smectic-A Ionic Liquid Crystal by Molecular Dynamics Simulation

Abstract

Five distinct crystal structures, based on experimental data or constructed manually, of ionic liquid [C14Mim][NO3] were heated in NPT molecular dynamics simulations under the same pressure such that they melted into the liquid crystal (LC) phase and then into the liquid phase. It was found that the more entropy-favored structure had a higher solid-LC transition temperature: Before the transition into the LC, all systems had to go through a metastable state with the side chains almost perpendicular to the polar layers. All those crystals finally melted into the same smectic-A LC structure irrelevant of the initial crystal structure.

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

“…While the structural properties are generally good, the dynamics are significantly slowed down. A secondary effect of the increased electrostatic interaction is an increase of the transition temperatures observed in the simulations [37]. A common workaround is to use higher temperatures to speed up the sampling of the phase space.…”

“…Computer simulations are a very useful tool with which to investigate the microscopic features of complex fluids. ILCs have been the subjects of several of such investigations with a variety of force field types: fully atomistic [33][34][35][36][37][38], coarse-grained [39][40][41] and highly coarse-grained [42][43][44][45][46]. In a recent combined experimental and simulation study, we investigated in detail the effect of the relative anion size on the thermal range of stability of the ionic smectic phase of a series of N-alkyl-3-methylpyridinium halides and trihalides [47].…”

Pathway for Water Transport through Breathable Nanocomposite Membranes of PEBAX with Ionic Liquid [C12C1im]Cl

“…A lot of studies have been dedicated to the analysis of structure and dynamics in bulk ionic liquids [ 38 , 39 , 40 , 41 , 42 , 43 ], whilst the number of papers dedicated to the confinement of these materials in organic and inorganic matrixes and to changes in IL structure and interfaces is somewhat limited [ 44 ]. When filling polymeric matrixes with ILCs, changes in the final properties of the nanocomposite systems can be experimentally detected by suitable tools [ 45 ]; however, the relationship between the low dimensionality of interface systems and fluidity of the interfaces becomes quite difficult to understand.…”

Phase coexistence in [C22/C1MIm]+[NO3]− ionic-liquid mixtures and first-order phase transitions from homogeneous liquid to smectic B by varying the cation ratio

“…Starting at about 15%, the system goes through a firstorder phase transition, after which some of the C 22 side chains aggregate locally to form small bundles ''floating'' in the polar ''solvent'', referred to as the nano-fragment liquid (NFL). In the NFL phase, the nonpolar chains in each bundle are parallelly aligned to each other, rather than being pushed by the continuous polar network into huddles as in the NSL phase, 5,6,39 but the bundles are randomly distributed without a global orientation. The second first-order phase transition from the NFL to the SmB ILC occurs in the range of 45%-50%.…”