Effect of different monomer precursors with identical functionality on the properties of the polymer network

TL;DR

This study uses molecular simulations to explore how different monomers with the same functionality influence the properties of polymer networks, revealing universal behaviors and a potential new phase transition related to brittleness.

Contribution

It demonstrates that chemically different monomers with identical functionality produce networks with universal graph properties and highlights a new phase transition linked to network topology and brittleness.

Findings

Young's modulus is nearly universal across different monomers.

Vitrification temperature is universal up to a certain network density.

Percolation of topological holes correlates with the onset of brittleness.

Abstract

Thermo-mechanical properties of polymer networks depend on functionality of the monomer precursors -- an association that is frequently exploited in materials science. We use molecular simulations to generate spatial networks from chemically different monomers with identical functionality and show that such networks have several universal graph-theoretical properties as well as near universal Young's modulus. The vitrification temperature is shown to be universal only up to a certain density of the network, as measured by the bond conversion. The latter observation is explained by the fact that monomer's tendency to coil enhances formation of topological holes, which, when accumulated in the network, amount to a percolating cell complex restricting network's mobility. This higher-order percolation occurs late after gelation and is shown to coincide with the onset of brittleness, as indicated by a sudden increase in the glass transition temperature. This phenomenon may signify a new type of phase transition in polymer materials.