Systematic and simulation-free coarse graining of multi-component polymeric systems: Structure-based coarse graining of binary polymer blends

Significance Statement

Polymer blends have been extensively studied in many experimental, simulation, and theoretical analyses owing to their importance in engineering as well as polymer science. As opposed to homopolymer melts, only a few researchers have performed coarse graining of polymer blends. Professor Qiang Wang’s group from Colorado State University recently proposed a systematic and simulation-free method for coarse graining of homopolymer melts. The researchers used integral-equation theories instead of many-chain molecular simulations. This was in the quest to obtain structural as well as thermodynamic attributes of original and coarse-grained systems, and to examine quantitatively how the pair potentials between coarse-grained segments and the thermodynamic attributes varied with the coarse-graining level. The authors applied their method to both the structure-based and the relative-entropy-based coarse graining of homopolymer melts.

Professor Qiang Wang extended from their previous study and proposed a systematic and simulation-free strategy for the structure-based coarse graining of multi-component polymeric systems using the polymer reference interaction site model (PRISM) theory. He later applied it as an example to a simple model system of binary polymer blends. The developed structure-based coarse graining ensured that the original and coarse-grained systems have the same intermolecular correlation functions entailing the coarse-grain segments. When it was applied to binary polymer blends, it didn’t change the spinodal curve irrespective of the original model system as well as closure used.

In addition, the author also evaluated quantitatively how the effective non-bonded pair potentials between the coarse-grained segments and the thermodynamic attributes of coarse-grained system varied with the coarse-graining level. He observed that the structure-based coarse graining did not yield thermodynamic consistency between the original and coarse-grained systems at any coarse-graining level.

The method developed was quite general and versatile.  Therefore, it could be applied to more complex chain models as well as complicated systems. The new method was much faster than those applying many-chain molecular simulations, therefore, efficiently solving the transferability issue in coarse graining. It further avoided the issues caused by finite-size effects as well as statistical uncertainties in many-chain molecular simulations. The proposed method by Professor Qiang Wang in conjunction with fine graining served well for the goal of multi-scale modeling of multi-component polymeric systems. His research work is published in Polymer.

Systematic and simulation-free coarse graining of multi-component polymeric systems: Structure-based coarse graining of binary polymer blends-Advances in Engineering

            Figure credit: Polymer Journal, volume 117 (2017), pages 315-330. (with permission)

About The Author

Dr. Qiang WANG obtained his PhD degree in Chemical Engineering in 2002 from University of Wisconsin – Madison, under the supervision of Prof. Juan de Pablo and Prof. Paul Nealey. His PhD dissertation was entitled “Molecular Study of the Structure and Morphology of Diblock Copolymers on Nano-Patterned Substrates”, where he used lattice Monte Carlo simulations, self-consistent field calculations, and strong-stretching theory to study the lamellae- and cylinder-forming diblock copolymers in bulk and under thin-film confinement. He then joined Prof. Glenn Fredrickson’s group at University of California – Santa Barbara as a postdoctoral researcher, where he worked on the self-consistent field theory and random-phase approximation of polyelectrolyte systems.

In August 2004, Dr. Wang was appointed as a tenure-track Assistant Professor in the Department of Chemical and Biological Engineering at Colorado State University, and was tenured and promoted to an Associate Professor in July 2010. His group combines advanced theories and computer simulation techniques to study at nano- to meso-scales (i.e., from sub-nanometers to micrometers) the behavior of nanostructured polymeric materials, including the self- and directed assembly of block copolymers, stimuli response of polymer brushes, and polyelectrolyte adsorption and layer-by-layer assembly.

His group has also been very actively developing the so-called “fast Monte Carlo simulations”, a class of novel Monte Carlo simulation methodologies suitable for the study of equilibrium properties of many-chain systems (e.g., polymer melts) with coarse-grained models. From January to August 2013, Dr. Wang took a sabbatical in Prof. Dr. Kurt Kremer’s group at the Max Planck Institute for Polymer Research in Mainz, Germany. Since then, his group has been working on the systematic and simulation-free coarse graining of polymeric systems.

Reference

Qiang Wang. Systematic and simulation-free coarse graining of multi-component polymeric systems: Structure-based coarse graining of binary polymer blends. Polymer, volume 117 (2017), pages 315-330.

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