Mesoscopic Modeling of Dynamic Tetra-PEG Hydrogel Networks

TL;DR

This paper presents a mesoscopic hybrid DPD/MC model for Tetra-PEG hydrogels that accurately captures their viscoelastic behavior and topological features, aiding the design of dynamic polymer networks.

Contribution

It introduces a novel mesoscopic simulation approach combining DPD and Monte Carlo methods to model reversible cross-links and polymer dynamics in hydrogels.

Findings

Model reproduces Maxwell-like viscoelastic response.

Relaxation time scales with bond kinetics and gel point.

Topological analysis reveals bond distribution and cluster formation.

Abstract

We introduce a mesoscopic model of dynamic Tetra-PEG hydrogel networks based on a hybrid Dissipative Particle Dynamics/Monte Carlo (DPD/MC) approach. Polymer chains are described by Finite Extensible Nonlinear Elastic (FENE) potential, while reversible cross-links are modeled with Morse potential and Monte Carlo bond exchange governed by Bell's force-dependent kinetics. After systematic calibration against theory and experiments, the model reproduces the characteristic Maxwell-like viscoelastic response of these networks. In particular, the relaxation time follows the expected scaling, $\tau_R \propto \tau_b (p - p_{\text{gel}})$, and the simulated storage moduli agree with experimental rheology. The mesoscopic resolution allows for graph-based topological analysis, where Tetra-PEG molecules and cross-links are represented as nodes and edges, providing access to bond distributions, fraction of dangling chains, and size of percolating clusters that are challenging to measure experimentally. Comparison with permanent-network predictions further suggests that dynamic bond exchange can affect bond distributions and delay the formation of a system-spanning cluster. This model bridges macromolecular bond kinetics and macroscopic mechanical properties, providing a complementary tool for rational design of dynamic polymer networks.