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Materials Characterization

Neutrons reveal key role of water in polyelectrolyte dynamics


Molecular dynamics simulation showing water (red) within the polyelectrolyte (blue), which leads to the enhanced dynamics observed in quasielastic neutron scattering.

Combined neutron scattering and computational results show that the charge on a water-dissolved polymer accelerates its dynamics through an increase in the amount of water contained within the molecule. Such polyelectrolytes, i.e. water-soluble polymers composed of charged groups, are important in numerous energy storage and conversion approaches, and understanding their dynamics is key to optimizing the efficiency in such applications. The current work shows that local interactions between the polymer and only the first few nearest neighbor water molecules drives the faster dynamics of polyelectrolyte. This water-driven mechanism of the polyelectrolyte dynamics is a surprise to the soft matter physics community since the current theories have been developed based on an average interaction between the polymer and water where local interactions don’t play a role. In addition to this scientific importance, the results provide guidance to the tailoring of the microstructure of polyelectrolyte-based materials to achieve substantial improvements via optimizing the water-polymer interaction.

For more information, please contact Wei-Ren Chen, chenw@ornl.gov.

Bin Wu, Yun Liu, Xin Li, Eugene Mamontov, Alexander I. Kolesnikov, Souleymane O. Diallo, Changwoo Do, Lionel Porcar, Kunlun Hong, Sean C. Smith, Li Liu, Gregory S. Smith, Takeshi Egami, and Wei-Ren Chen, “Charge-Dependent Dynamics of a Polyelectrolyte Dendrimer and Its Correlation with Invasive Water,” Journal of the American Chemical Society, DOI: 10.1021/ja3125959, Publication Date (Web): March 12, 2013.

 

 

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