Multipoint segmental repulsive potential for entangled polymer simulations with dissipative particle dynamics

Abstract

A model is developed for simulating entangled polymers by dissipative particle dynamics (DPD) using the segmental repulsive potential (SRP). In contrast to previous SRP models that define a single-point interaction on each bond, the proposed SRP model applies a dynamically adjustable multipoint on the bond. Previous SRP models could not reproduce the equilibrium properties of Groot and Warren's original DPD model [R. D. Groot and P. B. Warren, J. Chem. Phys. , 4423 (1997)] because the introduction of a single SRP induces a large excluded volume, whereas, the proposed multipoint SRP (MP-SRP) introduces a cylindrical effective excluded bond volume. We demonstrate that our MP-SRP model exhibits equilibrium properties similar to those of the original DPD polymers. The MP-SRP model parameters are determined by monitoring the number of topology violations, thermodynamic properties, and the polymer internal structure. We examine two typical DPD polymers with different bond-length distributions; one of them was used in the modified SRP model by Sirk [J. Chem. Phys. , 134903 (2012)], whereas the other was used in the original DPD model. We demonstrate that for both polymers, the proposed MP-SRP model captures the entangled behaviors of a polymer melt naturally, by calculating the slowest relaxation time of a chain in the melt and the shear relaxation modulus. The results indicate that the proposed MP-SRP model can be applied to a variety of DPD polymers.

Shear Flow and Relaxation Behaviors of Entangled Viscoelastic Nanorod-Stabilized Immiscible Polymer Blends

“…To capture entanglements in DPD polymer melt systems, 15,32,45 a nonbonded force F kl E is added between the polymer segments k and l that are not adjacent to each other (eq 2) 32,45 l…”

“…These results are in good agreement with previous studies. 15,44,45 Additionally, a head-to-head comparison of computing cost can be made between sDPD and mSRP. The a Each simulation box is cubic with a length of L. After an equilibration period, a data acquisition interval follows during which averages are taken for a given averaging interval.…”

“…Therefore, many methods to prevent polymer bond crossings in mesoscale simulation techniques have been proposed. 15,28,32,33,[37][38][39][40][45][46][47][48]54 Out of these many methods, segmental repulsive potentials (SRP) 28,32 between polymer bonds have been very popular for dissipative particle dynamics (DPD) and other mesoscopic models. 39,[41][42][43][44]46 As an advantage over other approaches, [47][48][49]54 SRP allow model parameters and their coarse-graining degree to be independently tuned.…”

“…39,[41][42][43][44]46 As an advantage over other approaches, [47][48][49]54 SRP allow model parameters and their coarse-graining degree to be independently tuned. When using SRP or its variants, 15,45 researchers strive to reduce the number of bond crossing events while still obtaining ideal chain statistics and minor disturbances to the original DPD model.…”

Fast and accurate computation of interactions between linear fiber segments

“…Discrete approaches treat each fiber as a connected sequence of elements which are governed by Newtonian mechanics. One approach uses a soft segmental repulsive potential (SRP), based on the shortest distance or a set of distances between fibers (bonds) to prevent line segments from passing through one another (Iwaoka et al , 2018; Sirk et al , 2012). Another approach is to represent a straight fiber segment as a tightly packed sequence of beads which have pairwise particle-based interactions with beads on other fiber segments (Buehler, 2006; Picu and Sengab, 2018).…”