Hydrodynamic Interactions and Entanglements of Polymer Solutions in Many-Body Dissipative Particle Dynamics.

Xin Yong

doi:10.3390/polym8120426

Abstract

Using many-body dissipative particle dynamics (MDPD), polymer solutions with concentrations spanning dilute and semidilute regimes are modeled. The parameterization of MDPD interactions for systems with liquid–vapor coexistence is established by mapping to the mean-field Flory–Huggins theory. The characterization of static and dynamic properties of polymer chains is focused on the effects of hydrodynamic interactions and entanglements. The coil–globule transition of polymer chains in dilute solutions is probed by varying solvent quality and measuring the radius of gyration and end-to-end distance. Both static and dynamic scaling relations for polymer chains in poor, theta, and good solvents are in good agreement with the Zimm theory with hydrodynamic interactions considered. Semidilute solutions with polymer volume fractions up to 0.7 exhibit the screening of excluded volume interactions and subsequent shrinking of polymer coils. Furthermore, entanglements become dominant in the semidilute solutions, which inhibit diffusion and relaxation of chains. Quantitative analysis of topology violation confirms that entanglements are correctly captured in the MDPD simulations.

Highlights

Because of the fast evolution of polymer science and nanotechnologies, polymeric materials with precisely tailored functionalities, such as block copolymer thin films and polymer nanocomposites, become central to a wide range of emerging applications
In addition to the Flory–Huggins approach employed in this work, Hildebrand solution theory approach [58,59] and more advanced ab-initio methodologies [60] may be adapted in many-body dissipative particle dynamics (MDPD) to simulate ternary mixtures of beads dissimilar in both size and chemistry
The surface tension of MDPD binary mixtures as a function of the χ parameter agrees well with the classical van der Waals theory, despite a higher critical point found from the fitting than the classical value

Summary

Introduction

Because of the fast evolution of polymer science and nanotechnologies, polymeric materials with precisely tailored functionalities, such as block copolymer thin films and polymer nanocomposites, become central to a wide range of emerging applications. In order to achieve versatile properties and functionalities of the macroscopic materials, polymeric building units with increasingly smaller sizes and different types of chemistry are integrated into more and more complex structural hierarchy in controlled and synergistic manners. This demand challenges manufacturing processes, in which one must close the gap between adjusting macroscopic characteristics and controlling micro-nanostructures of building blocks. An initial liquid precursor with solutes and/or dispersed moieties transforms into a solid material upon evaporation. The complex interplay among polymer, solvent, and other components in the evaporating mixtures is not fully understood; in-situ experimental characterization of non-equilibrium multi-component systems across multiple length and time scales is still difficult

Methods

Results

Conclusion