Heterogeneity Effects in Highly Cross-Linked Polymer Networks

Abstract

Despite their level of refinement, micro-mechanical, stretch-based and invariant-based models, still fail to capture and describe all aspects of the mechanical properties of polymer networks for which they were developed. This is for an important part caused by the way the microscopic inhomogeneities are treated. The Elastic Network Model (ENM) approach of reintroducing the spatial resolution by considering the network at the level of its topological constraints, is able to predict the macroscopic properties of polymer networks up to the point of failure. We here demonstrate the ability of ENM to highlight the effects of topology and structure on the mechanical properties of polymer networks for which the heterogeneity is characterised by spatial and topological order parameters. We quantify the macro- and microscopic effects on forces and stress caused by introducing and increasing the heterogeneity of the network. We find that significant differences in the mechanical responses arise between networks with a similar topology but different spatial structure at the time of the reticulation, whereas the dispersion of the cross-link valency has a negligible impact.

Predicting Mechanical Constitutive Laws of Elastomers with Mesoscale Simulations

“…As demonstrated recently, the procedure by which the initial network is generated plays a prominent role with respect to a subsequent mechanical response. Here we have extended the process described before 15 to include entanglements.…”

“…In this paper, we use an intermediate scale to describe the polymer network. The model we introduce is built upon a previous model, where only the topological constraints were taken into account. To capture the strain softening regime at small deformation, it is necessary to introduce entanglements as special topological constraints. − The extension to add the modeling of entanglements explicitly is a major improvement with respect to the previous version of the model.…”

Effect of Polymer Composition and Morphology on Mechanochemical Activation in Nanostructured Triblock Copolymers

“…[29][30][31] However, modeling based on rubber elasticity theory and coarse-grained simulations of random networks both suggest that inhomogeneity in the crosslink distribution leads to stress concentration in a small number of chains, which in turn decreases the overall activation efficiency. [32][33][34] Self-assembled triblock copolymers are an attractive platform for investigating how network structure affects mechanochemical activation because they can be designed such that the elastically-effective strands in the midblock are the same length throughout the material, and the network connectivity can be tuned by changing the block fractions, which in turn change the self-assembled morphology. 35,36 A small number of reports have offered preliminary evidence that block copolymer self-assembly can indeed be used to facilitate mechanochemical activation in polymeric materials.…”

A Simple Solvent-Free Strategy of Polybenzoxazine Film Elaboration with Controllable Performance via Molecular Weight Regulation between Cross-Linking Knots

“…8,43 It is known that the properties of materials (e.g., mechanical) are determined by the topology of the network structure (i.e., regular or random). 44 Also, the physical− chemical properties of the polymer network (e.g., glass transition temperature and mechanical and viscoelastic proper-ties) depend strongly on the spacer length between crosslinkers. 45 Thus, a higher molecular weight of the polypropylene glycol/polyethylene glycol block will ensure a higher network mobility and reduce the glass transition temperature, thus resulting in lower inelastic properties (such as compressive and tensile yield strength).…”

“…It is known that the properties of materials (e.g., mechanical) are determined by the topology of the network structure (i.e., regular or random) . Also, the physical–chemical properties of the polymer network (e.g., glass transition temperature and mechanical and viscoelastic properties) depend strongly on the spacer length between cross-linkers .…”