Experiments and Simulations: Enhanced Mechanical Properties of End-Linked Bimodal Elastomers

Abstract

We report on stress−strain and swelling results for polydimethylsiloxane bimodal networks, studied both experimentally and via Monte Carlo simulations. These end-linked networks were formed with negligible extent of soluble fractions, and reasonable agreement is found between experimental results and simulation data. We examine the variation in microstructure for networks with different concentrations of short chains. When the concentration of short chains is low, these chains aggregate during the end-linking process and lead to a heterogeneous network structure, while networks formed with higher short chain concentrations are more homogeneous. Short chains that are long enough to initially have a Gaussian conformation also produce the characteristic stress upturn and enhanced toughness previously reported in bimodal networks with non-Gaussian short chains. We find that it is the limited extensibility of the short chains at high concentrations and not the cluster formation of short chains at low concentrations that leads to the enhanced mechanical properties of these elastomers.

The Current State of Silicone-Based Dielectric Elastomer Transducers

“…Bimodal networks, which consist of a mixture of very short and relatively long chemically identical polymer chains, can be used as a tool to improve the mechanical properties of silicone networks . Several studies have investigated the unexpected high tear and ultimate strength of bimodal networks .…”

“…Furthermore, these relatively long chains retard the rupture process and are responsible for the extensibility of the network . Therefore, bimodal networks exhibit both significant ultimate stress and major ultimate strain . Bimodal networks can be created with a random distribution of short polymer chains within the long chains (homogeneous bimodal networks) or as heavily cross‐linked short chain clusters joined to the long chain network (heterogeneous bimodal networks) …”

Thermoreversible associating polymer networks. I. Interplay of thermodynamics, chemical kinetics, and polymer physics

“…Coarse-grained modelling with the goal of studying the dynamics of AP systems by analogy is the only currently feasible approach for bulk systems, so we make no attempt to mimic specific chemistries. The only published simulations of which we are aware that model AP networks with specific chemistries [84,90] are pure Monte Carlo studies that used a very coarse-grained (lattice) bond-fluctuation model [91] and focused on static properties.…”

Toughening rubbers with a hybrid filler network of graphene and carbon nanotubes

“…[1][2][3][4] Recently, Creton et al 5 developed an alternative double/triple-network structure by using sequential interpenetrating polymerization of acrylate monomers. This ability enables wide applications of rubbers in industry and our daily lives, such as tyres, seals, dampers, gloves and shoes.…”