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Single-Molecule Polymer Chemistry

The Shen group focuses on utilizing state-of-the-art single-molecule spectroscopy to investigate the properties of polymeric materials and their potential applications in catalysis and bioseparation. Unlike conventional ensemble measurements, single-molecule spectroscopy analyzes one probing molecule at a time to reveal the performances dictating subpopulations within a system. Its subdiffraction limited localization enables the microscopic to mesoscopic mapping. Moreover, the real-time observation under millisecond resolution enables the dynamic study of complex processes. With this main approach, the Shen group aims to study the following.

• Developing advanced microscopy approaches.

Thanks to the developments of fluorescence microscopy, researchers nowadays have a non-destructive approach to observe many soft matters and biological systems in-situ. The persistent efforts in the past two decades have broken the diffraction limits, allowing an optical microscope to achieve nanometer precisions. We now understand many systems better than ever. However, the needs for more capable observation tools will never stop. The Shen group will use phase modulations to develop novel imaging methods that enable higher precision and wider observation ranges.   

• Spatially resolved polymerization kinetics.

The world polymer production surpassed 300 megatons in 2015 and is still expanding rapidly. However, a detailed description of the polymerization kinetics lacks because there are some “anomalous” behaviors associated with the reaction types, such as auto-acceleration, radical trapping, gelation, and diffusion induced termination. Such anomalous processes usually result in severe polydispersity in chain sizes within the bulk polymer materials, ultimately downgrading the performances of functional polymers. The Shen group strives to understand how micro-environment affects the polymerization kinetics. The goal is to understand the polymerization mechanisms better and design new strategies to prepare more homogeneous polymers.

• Synthetic polymer membranes for protein separations.

Proteins carry out vital physiological activities that are widely used in the pharmaceutical and food industries. Each protein exhibits unique physiological functionalities requiring high purity and concentrations when used for manufacturing highly specific products. Chromatography utilizing synthetic polymers as the stationary phase materials is the industrial standard in downstream processing, which may account for as much as 50% of the overall cost to bring a protein product to the market. Consequently, it is critical to understand the dynamics of protein-synthetic polymer interactions, because any such insights will in turn benefit the designing of high-efficient, anti-fouling stationary phase materials to reduce the manufacturing costs for protein-based products. The Shen group uses single-molecule spectroscopy to map out the protein-polymer interactions in real-time.

Selected Publications

1. H. Shen, L.J. Tauzin, R. Baiyasi, W. Wang, N.A. Moringo, B. Shuang, C.F. Landes, “Single Particle Tracking: From Theory to Biophysical Applications”, Chemical Reviews, 2017, 117, 7331-7376.

2. H. Shen, L. Tauzin, W. Wang, B. Hoener, B. Shuang, L. Kisley, A. Hoggard, C.F. Landes, “Single-Molecule Kinetics of Protein Adsorption on Thin Nylon 6,6 Films”, Analytical Chemistry, 2016, 88, 9926-9933.

3. H. Shen, X. Zhou, N. Zou, P. Chen, “Single-Molecule Kinetics Reveals a Hidden Surface Reaction Intermediate in Single-Nanoparticle Catalysis”, Journal of Physical Chemistry C, 2014, 118, 26902-26911.