Development of new coarse-grained models for chromonic liquid crystals: insights fromtop-downapproaches

Abstract

Two top-down coarse-grained molecular simulation models for a chromonic liquid crystal, 3,6,7,10,11-hexa-(1,4,7-trioxa-octyl)-triphenylene, are tested. We use an extension of the wellknown MARTINI model and develop a new coarse-grained model based on statistical associating fluid theory (SAFT)-γ perturbation theory. For both models, we demonstrate self-assembly in the isotropic phase of the chromonic and we test the effectiveness of both models in terms of the structures of the chromonic aggregates that are produced in solution and the thermodynamics of association. The latter is tested by calculations of the potential of mean force for dimers in solution, which measures the strength of molecular association. SAFT-γ provides valuable insights into the thermodynamics of assembly. Exploration of a range of interactions between unlike sites demonstrates that chromonic self-assembly only occurs in a small parameter space where the hydrophilic-lipophilic balance between aromatic core and ethylene oxide chains is optimal. Outside of this balance, chromonic self-assembly is replaced by the formation of conglomerates of molecules or short stacks. ARTICLE HISTORY

Aggregation Behavior of Model Asphaltenes Revealed from Large-Scale Coarse-Grained Molecular Simulations

“…In particular, the CG parametrization of polycyclic aromatic hydrocarbons (PAHs), which constitute the aromatic regions in asphaltenic structures, connote some further challenges [63][64][65][66][67] . In a contribution which is very relevant to this study, von Lilienfeld and Andrienko 44 coarse-grain polycyclic aromatic hydrocarbons by fitting effective Lennard-Jones potentials to density-functional theory calculations, showing that the potential parameters of the CG units are specific to the aromatic molecule in the study.…”

Expanding the Applications of the SAFT-γ Mie Group-Contribution Equation of State: Prediction of Thermodynamic Properties and Phase Behavior of Mixtures

“…A heteronuclear model is implemented in SAFT-γ Mie, and a Mie (generalized Lennard-Jones) potential of variable repulsive and attractive ranges is used to represent the segment–segment group interactions. As evidenced by the growing number of published works − in which SAFT-γ Mie has been employed, the use of the approach is becoming widespread, not only in the traditional sense of GC modeling, but also as a basis for the development of coarse-grained force fields that are finding application in molecular simulations. − ,,,,,,,− ,,, …”

“…As evidenced by the growing number of published works 75−125 in which SAFT-γ Mie has been employed, the use of the approach is becoming widespread, not only in the traditional sense of GC modeling, but also as a basis for the development of coarse-grained force fields that are finding application in molecular simulations. [77][78][79][80]85,86,92,97,101,106,[110][111][112]116,121,125 In more conventional equation-of-state modeling, the range of fluids considered and the contexts in which SAFT-γ Mie have been applied continue to broaden. Sadeqzadeh et al 84 used SAFT-γ Mie to study the phase behavior of aqueous mixtures comprising acetone, alkanes, and alkyl carboxylic acids.…”

Oligomer/Polymer Blend Phase Diagram and Surface Concentration Profiles for Squalane/Polybutadiene: Experimental Measurements and Predictions from SAFT-γ Mie and Molecular Dynamics Simulations

“…Coarse-grained (CG) simulation models − provide a way of studying the influence of oligomers at a molecular level. Here, accessible times scales can be many orders of magnitude longer than those available from atomistic simulations.…”

“…In contrast to bottom-up models, top-down approaches, based on SAFT theories, − and MARTINI-like models ,− focus on capturing macroscopic thermodynamic experimental information in the development of CG polymer models. Hence, they might be expected to perform better under conditions where oligomer–polymer phase separation may be present.…”