# Structure and phase behavior of polymer-linked colloidal gels

## TL;DR

This study demonstrates how polymer-linked colloidal gels can be designed with tunable phase behavior and microstructure by varying polymer size and concentration, offering a scalable approach to create resilient, equilibrium gel materials.

## Contribution

It introduces a model for colloid-polymer mixtures showing how polymer molecular weight and blends influence gel formation and microstructure, expanding the design space for equilibrium gels.

## Key findings

- Longer linkers expand the equilibrium gel formation window.
- Blends of different-sized linkers enable microstructure variation.
- Polymer size and concentration effectively tune phase behavior.

## Abstract

Low-density "equilibrium" gels that consist of a percolated, kinetically arrested network of colloidal particles and are resilient to aging can be fabricated by restricting the number of effective bonds that form between the colloids. Valence-restricted patchy particles have long served as one archetypal example of such materials, but equilibrium gels can also be realized through a synthetically simpler and scalable strategy that introduces a secondary linker, such as a small ditopic molecule, to mediate the bonds between the colloids. Here, we consider the case where the ditopic linker molecules are low-molecular-weight polymers and demonstrate using a model colloid-polymer mixture how macroscopic properties such as the phase behavior as well as the microstructure of the gel can be designed through the polymer molecular weight and concentration. The low-density window for equilibrium gel formation is favorably expanded using longer linkers, while necessarily increasing the spacing between all colloids. However, we show that blends of linkers with different sizes enable wider variation in microstructure for a given target phase behavior. Our computational study suggests a robust and tunable strategy for the experimental realization of equilibrium colloidal gels.