Controlling the properties of colloidal gels with polymer linkers

Colloidal gels have captured the interest of researchers due to the possibility to tune their various properties by incorporating nanoparticles. For example, a gel’s optical properties can be altered by filling it with nanoparticles that interact with light. For these purposes, the ability to control how close the nanoparticles are to each other, known as the gel’s microstructure, is paramount to the field.

However, the preparation of equilibrium colloidal gels, where nanoparticles are evenly distributed throughout the solution, is challenging. Non-equilibrium gels evolve significantly over time, leading to structural variation and phase separation.

Truskett et al. showed that polymer linkers may be used to exert control over both the gel’s microstructure and phase behavior.

“The traditional path is to rapidly quench the material under conditions where particles would like to separate into low-concentration and high-concentration phases,” said author Thomas Truskett.

Instead of quenching, the team used polymer linkers mixed with spherical colloids to create their gel. They found that they could control the gel’s phase behavior, such as the threshold for phase separation, by changing the linker length. The addition of a second set of linkers with a different length allowed the researchers to gain control over the gel’s microstructure.

“We also hope to be able to design linkers that we can dynamically replace in order to reconfigure the gel and give it a new set of properties on demand,” said Truskett.

Next, they plan to study how the linkers may allow for control over macroscopic properties of a gel, such as its mechanical strength.

Source: “Structure and phase behavior of polymer-linked colloidal gels,” by Michael P. Howard, Ryan B. Jadrich, Beth A. Lindquist, Fardin Khabaz, Roger T. Bonnecaze, Delia J. Milliron, and Thomas M. Truskett, Journal of Chemical Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5119359 .