Graphene oxide (GO) is often referred as a 2D colloid, which can be dispersed in water and form nematic liquid crystal (LC) phase. The good dispersity and the ability to form the LC phase enables the solution processing of GO; thus, GO LC has been actively employed in high-performance graphene-based fibers or films applications through solution processing. While GO LC exhibits extraordinary physical properties of high mechanical strength, tunable bandgap or good electrical/thermal conductivity, the performance of GO LC applications can be dependent on their colloidal properties in solution. In this regard, we systematically study the stable dispersion of GO in polymer solutions and examine how polymer influence the microstructure and rheological properties of GO suspension. 

The following topics are of current interest to our group.

A. Microstructure and rheological properties of graphene oxide dispersions

B. Polymer crystallization in extreme confinement with graphene oxide

C. Dispersion and rheological properties of MXene

A. Microstructure and Rheological Properties of Graphene Oxide Dispersions

Graphene oxide (GO) exhibits good dispersibility and colloidal stability in an aqueous solution based on its functional groups on the basal plane and edges. These properties enable solution processing of GO dispersion for various forms of GO-based products such as fiber, membrane, aerogel, etc. Depending on the structure of the GO dispersion, the electrical and mechanical properties of the final product may change, and certain rheological properties are required depending on the processing. Our group investigates microscopic structural changes according to specific factors and further discusses macroscopic changes in rheological properties. Through this, better process conditions and treatment procedures are suggested according to the purpose.

Representative paper

1)  Overcoming Challenges in Colloidal and Chemical Stability of Graphene Oxide with Exploration of Dispersing Solvent (Small, 2025)

2) Is Low Polydispersity Always Beneficial? Exploring the Impact of Size Polydispersity on the Microstructure and Rheological Properties of Graphene Oxide (ACS Appl. Mater. Interfaces, 2024)

3) Additive-Free Gelation of Graphene Oxide Dispersions via Mild Thermal Annealing: Implications for 3D Printing and Supercapacitor Applications (Adv. Mater., 2024)

4) Unifying Dispersion Properties of Graphene Oxide Suspensions via Interlayer Spacing Control: Insights for Universal 2D Colloid Behavior (Carbon, 2023)

5) Continuous Structural Deformation of Graphene Oxide Liquid Crystal Colloids Under Shear for Hydrogel Films (Carbon, 2023)

6) Universal Alignment of Graphene Oxide in Suspensions and Fibers (ACS Nano, 2021)

B. Polymer Crystallization in Extreme Confinement with Graphene Oxide 

Graphene oxide (GO) is known to promote crystallization kinetics and change the crystalline morphology for semicrystalline polymers. Previous studies reported that the large specific surface area of GO can provide nucleation sites, which enhances the polymer crystallization on GO reducing the nucleation barrier. However, the crystallization kinetics can be more complex such that the crystallization can be enhanced or suppressed depending on the cooling rate or the GO content. In addition, the GO-polymer interactions at the GO interface can play an important role in changing crystallization kinetics. 

Representative paper

1) Tailored Growth of Graphene Oxide Liquid Crystals with Controlled Polymer Crystallization in GO-polymer Composites (Nanoscale, 2021)

2) Tailored Colloidal Stability and Rheological Properties of Graphene Oxide Liquid Crystals with Polymer Induced Depletion Attractions (ACS Nano, 2018)

3) Wide Concentration Liquid Crystallinity of Graphene Oxide Aqueous Suspension with Interacting Polymers (Mater. Horiz., 2017)

C. Dispersion and Rheological Properties of MXene

MXenes(Mn+1XnTx) are a two-dimensional(2D) material that shows high electrical conductivity and excellent mechanical properties. MXenes are widely used for energy storage, electromagnetic interference shielding, and catalysis due to their superior properties. As these applications are processed in their dispersion states and performance can vary depending on the particle structure, understanding the fundamental characteristics of MXenes in dispersion states becomes crucial. We are interested in investigating the structure-rheological property relationship with the occurrence of oxidation and polymer addition.