Microstructure and Mechanical Properties of Jammed Dispersion of Nanogels

Abstract

This study employs dissipative particle dynamics simulations to investigate the equilibrium microstructure and mechanical properties of jammed nanogel dispersions in a good solvent. The nanogels, composed of cross-linked linear polymers, exhibit impenetrability. Significant changes in size (radius of gyration) and shape (asphericity parameter) occur beyond a critical concentration (e.g., 15 wt %), resulting in densely packed configurations. The coordination number increases with rising concentration and stabilizes at a constant (approximately 13) for a jammed structure. For the jammed dispersion (25 wt %), rheological measurements reveal shear-thinning behavior and the presence of a static yield stress. Furthermore, oscillatory tests confirm the dominance of the storage modulus, indicating solid-like behavior. According to the compressive test, the Young’s modulus increases with the nanogel concentration due to denser packing. Free relaxation tests show an elastic response for small strains but a plastic response for large strains. This comprehensive analysis elucidates the relationship between the microstructure of nanogel dispersions and their solid-like characteristics.