# A molecular dynamics study of the structure and dynamics of screened polyelectrolyte complex materials

## TL;DR

This paper uses simulations to study the structure and behavior of compleximers, a new type of material combining properties of thermoplastics and thermosets.

## Contribution

The study reveals how charge density and architecture affect the dynamics and glass transition temperature of compleximers.

## Key findings

- Reducing charge per unit mass lowers density, cohesive energy, and charged bead contacts.
- Structural changes enhance dynamics and lower the glass transition temperature (Tg).
- Compleximers show universal fragility and correlation between relaxation time and rattling amplitude.

## Abstract

Compleximers are a novel class of materials that combine the properties of thermoplastics and thermosets, due to their reversible network structure facilitated by ionic interactions moderated by hydrophobic attenuators. In this study, we investigate the structural and dynamic properties of various architectures of these relatively unexplored, water-free polyelectrolyte complex materials using molecular dynamics simulations. We find that decreasing the number of charges per unit mass, either by increasing the length of neutral side chains or by decreasing the charge density of the polymers, leads to a decrease in density. This is related to a decrease in cohesive energy and in the number of contacts between oppositely charged beads. These structural changes result in an enhancement of the dynamics and a lowering of the glass transition temperature (Tg), which correlates with the number of oppositely charged contacts in the first coordination shell of the monomers. The fragility, represented in Angell plots, was found to be universal for all systems, irrespective of charge density. Compleximers also follow the universal correlation between the structural relaxation time and the rattling amplitude in glass-forming liquids.

The structural and dynamic properties of compleximers, a novel class of polymer materials crosslinked by attenuated ionic bonds between oppositely charged polymers, are studied using molecular dynamics simulations.