Simulation studies of soft matter: generic statistical properties and chemical details

Abstract

Abstract. The relation between atomistic structure, architecture, molecular weight and material properties is a basic concern of modern soft material science. This by now goes far beyond standard properties of bulk materials. A typical additional focus is on surface or interface aspects or on the relation between structure and function in nanoscopic molecular assemblies. This all implies a thorough understanding on many length and correspondingly time scales ranging from (sub)-atomic to macroscopic. At this point computer simulations are playing an increasingly important, if not the central role. Traditionally simulations have been separated in two main groups, namely simplified models to deal with generic or universal aspects of polymers, i.e. critical exponents, and those employing classical force field simulations with (almost) all atomistic detail, i.e. for the diffusion of small additives in a small "sample". Still characteristic problems, which require huge systems and/or long times in combination with a chemistry specific model, cannot be tackled by these methods alone. More recently with the development of scale bridging or multi scale simulation techniques, these different approaches have been combined into an emerging rather powerful tool. It is the purpose of this contribution to give a few examples of how such an approach can be used to understand specific material properties.

Temperature-Dependence of Persistence Length Affects Phenomenological Descriptions of Aligning Interactions in Nematic Semiconducting Polymers

“…In conjugated polymers, mesoscopic properties of morphologies with uniaxial (nematic) LC order can be theoretically understood using Maier–Saupe (MS) models. − Approaches based on MS models have been successful in describing nematic mesophases for a broad range of molecular chemistries, e.g., from rod-like derivatives of poly­(alkoxyphenylenevinylene) to flexible polyalkylthiophenes. , MS descriptions belong to the class of minimal (or generic , ) models of polymer physics. Minimal models represent molecular architecture and interactions in simplified manner, retaining only some key mesoscopic features.…”

“…Minimal models represent molecular architecture and interactions in simplified manner, retaining only some key mesoscopic features. They are deeply rooted , in universalities characterizing the long-wavelength behavior of various classes of polymer systems . Following the ideas of universality, MS models describe the architecture of conjugated polymers through simple worm-like chain (WLC) representations.…”

“…, f r o m r o d -l i k e d e r i v a t i v e s o f p o l y -(alkoxyphenylenevinylene) 32 to flexible polyalkylthiophenes. 25,36 MS descriptions belong to the class of minimal 39 (or generic 40,41 ) models of polymer physics. Minimal models represent molecular architecture and interactions in simplified manner, retaining only some key mesoscopic features.…”

Transferability of a coarse-grained atactic polystyrene model: the non-bonded potential effect

“…1,12,13,30,31,34,52 Among these, as a very common functional form for the pair-potential, the Lennard-Jones (LJ) type potential has been widely employed to construct CG non-bonded potentials for bio-molecular and polymer systems with varied success. 19,26,[54][55][56][57][58] For example, Marrink and coworkers use the standard LJ 12-6 function to describe the non-bonded This journal is © the Owner Societies 2016 interactions of CG particles in the MARTINI force field. 12,30,31,34,43,59 Following a top-down approach by extensive calibration of the non-bonded interaction parameters against experimental data, the resulting CG models successfully reproduce several key structural and thermodynamic properties 59 of the bio-molecular and carbohydrate systems.…”

Hybrid description of complex molecules

“…There exists several systematic and rigorous ways to obtain CG potentials from MD [23,24]. While static properties of the CoM can be exactly reproduced by the CG potential, dynamic properties are not always captured and ad hoc time rescaling has been a usual remedy to get agreement between CG and AA descriptions [25,26]. This shortcoming of CG potentials are attributed to friction and stochastic forces that arise from the elimination of degrees of freedom in addition to CG potentials [12].…”