Soft Matter

Since Pierre-Gilles de Gennes gave his famous Nobel lecture on Soft Matter, these “complex” and “flexible” physical systems have gained increasing interest over the past three decades. Here, at City U, we aim to use the state-of-the-art instruments to understand the unique behaviors of soft matter at the surface and interface and further develop new applications based on the newly found properties of soft matter.

The evolution of a glassy polymer nano-step measured by in situ AFM

Direction 1. Polymers Under Confinement

As the thickness of polymer films reduces to 40 nm, glass transition temperature (Tg) begins to decrease. After more than 20 years of intense research from many talents around the world, it has been recognized that the presence of a liquid-like surface of glassy polymers is responsible for the suppressed Tg of polymer thin films. In the past 15 years, more attention has been paid to the dynamics of this liquid-like surface in glassy polymers because this liquid-like layer is believed to have higher mobility than that in the bulk. No doubt, deeply understanding the properties of the polymer surface is essential for polymer applications at the nanoscale.​

  1. Y. Chai, T. Salez, J. D. McGraw, M. Benzaquen, K. Dalnoki-Veress, E. Raphaël, and J. A. Forrest,
    A Direct Quantitative Measure of Surface Mobility in a Glassy Polymer, Science, 343 (6174), 994-999, 2014

  2. Y. Chai, T. Salez, J. A. Forrest,
    Using Mw dependence of surface dynamics of glassy polymers to probe the length scale of free surface mobility, Macromolecules 53 (3), 1084-1089, 2020

  3. T. P. Russell and Y. Chai,
    Putting the Squeeze on Polymers: A Perspective on Polymer Thin Films and Interfaces, Macromolecules, 50 (12), 4597–4609, 2017

Direction 2. Soft Matter Self-Assembly

Self-assembly of soft matter largely exists in nature, like a school of fish, proteins assembled in milk, the formation of bio-films. In our lab, we try to understand the fundamental science of the assembly behavior of soft matter at the interface by using the state-of-the-art instruments.

  1. Y. Chai, J. Hasnain, K. Bahl, D. L, P. Geissler, P. Y. Kim, Y. Jiang, P. Gu, S. Li, D. Lei, B. A. Helms, T. P. Russell, P. D. Ashby. Science Advances, 6(48) eabb8675, 2020

  2. Y. Chai, A. Lukito, Y. Jiang, P. D. Ashby, T. P. Russell,
    Fine tuning the packing density of nanoparticles through ionic strength, Nano Letters, 17 (10), 6453-6457, 2017

  3. P. Gu#, Y. Chai#, H. Hou, G. Xie, Y. Jiang, Q. Xu, F. Liu, P. D. Ashby, J. Lu, T. P. Russell,
    Stabilizing Liquids Using Interfacial Supramolecular Polymerization. Angew. Chemie. 131, 12240–12244, 2019

Direction 3. Liquid and Soft Devices

Using the directed self-assembly of soft matter to make liquid and soft devices that can be used for energy storage, information processing, and biomedicine.

  1. X. Liu, N. Kent, A. Ceballos, R. Streubel, Y. Jiang, Y. Chai, P. Y. Kim, J. Forth, F. Hellman, S. Shi, D. Wang, B. A. Helms, P. D. Ashby, P. Fischer, T. P. Russell,
    Science, 365 (6450), 264-267, 2019

  2. G. Xie, J. Forth, Y. Chai, P. D. Ashby, B. A. Helms, T. P. Russell,
    Compartmentalized, All-Aqueous Flow-Through-Coordinated Reaction Systems, Chem, 2019

  3. W. Feng, Y. Chai, J. Forth, P. D. Ashby, T. P. Russell, B. A. Helms,
    Harnessing liquid-in-liquid printing and micropatterned substrates to fabricate 3-dimensional all-liquid fluidic devices, Nature Communications, 10 (1), 1095, 2019

Soft Matter Lab @ CityU