May 7, 2018
11:00 AM - 12:00 PM
Speaker: Chi Wu
Wei Lun Professor of Chemistry
The Chinese University of Hong Kong
Title: "Anti-biofouling: How a polymer brush repels proteins and our novel integrated design"
Grafting a layer of chains on a surface to form a polymer brush has been considered as an effective approach to make it anti-biofouling (less protein adsorption). The anti-biofouling property has been qualitatively attributed to the hydration of such a polymer brush with a layer of immobile water molecules and the steric effect; namely, the adsorption decreases monotonically as the polymer grafting density (σ) increases. However, there is no quantitative and satisfactory explanation why the adsorption starts to increase when σ is sufficiently high and why polyethylene glycol (PEG) still remains as one of the best to repel proteins. We have looked the captioned question from another angle: the entropic elasticity instead of the protein-surface interaction, i.e., the enthalpy change.
Considering that each grafted chain is confined inside a cylindrical “pore/tube” made of its neighboring chains, as shown in the right figure, we found its optimal length by minimizing its free energy (A) that contains the exclude volume interaction and the chain elasticity (both of them have an entropic nature) [1, 2]; estimated how A depends on σ and the chain length (L); and calculated its thermal energy-agitated chain conformation fluctuation that slows down the adsorption kinetically. After comparing A with the thermal energy, we are able to predict how both L and affect the protein repelling and explain why PEG performs better than others. Our predictions are surprisingly and quantitatively comparable with those literature results [3, 4].
We will also illustrate how to develop some novel anti-biofouling coatings for shipyard/marine applications by using an integrated design that combines different existing strategies; namely, the self-polishing, the self-structure and the self-generated soft and dynamic surface [5, 6].
1. Fan Jin, Chi Wu, Physical Review Letters, 96, 237801 (2006)
2. Lianwei Li, Cheng He, Weidong He, Chi Wu, Macromolecules, 45, 7583-7589 (2012).
3. Tengjiao Hu, Chi Wu, Physical Review Letters, 83, 4105-4107 (1999)
4. Guangming Liu, Yijian Chen, Guangzhao Zhang, Shihe Yang Physical Chemistry Chemical Physics, 9, 6073-6082 (2007)
5. Laiyong Xie, Fei Hong, Chuanxin He, Chunfeng Ma, Jianhong Liu, Guangzhao Zhang, Chi Wu, Polymer, 52, 3738-3744 (2011)
6. Fei Hong, Laiyong Xie, Chuanxin He, Jianhong Liu, Guangzhao Zhang, Chi Wu, Journal of Materials Chemistry B, 1, 2048-2055 (2013)