Modeling the Nanophase Structural Dynamics of Phenylated Sulfonated Poly Ether Ether Ketone Ketone (Ph-SPEEKK) Membranes as a Function of Hydration
Solvated phenylated sulfonated poly ether ether ketone ketone (Ph-SPEEKK) membranes in the presence of hydronium ions were modeled by classical molecular dynamics simulations. The characterization of the nanophase structure and dynamics of such membranes was carried out as a function of the water content lambda, where lambda is the number of water molecules per sulfonate group, for lambda values of 3.5, 6, 11, 25, and 40. Analysis of pair correlation functions supports the experimental observation of membrane swelling upon hydration as well the increase in water and hydronium ion diffusion with increasing lambda. While the average number of hydrogen bonds between hydronium ions and sulfonate groups is dramatically affected by the hydration level, the average lifetime of the hydrogen bonds remains essentially constant. The membrane is found to be relatively rigid and its overall flexibility shows little dependence on water content. Compared to Nafion, water and ion diffusion coefficients are considerably smaller at lower hydration levels and room temperature. However, at higher lambda values of 25 and 40 these coefficients are comparable to those in Nafion at a lambda value of 16. This study also shows that water diffusion in Ph-SPEEKK membranes at low hydration levels can be significantly improved by raising the temperature with important implications for proton conductivity.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1009725
- Report Number(s):
- PNNL-SA-76059; 24811; 40083; KC0302020; TRN: US201107%%834
- Journal Information:
- Journal of Physical Chemistry B, 115(8):1817-1824, Vol. 115, Issue 8; ISSN 1520-6106
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CORRELATION FUNCTIONS
DIFFUSION
ETHERS
FLEXIBILITY
HYDRATION
HYDROGEN
KETONES
LIFETIME
MEMBRANES
OXONIUM IONS
PROTONS
SIMULATION
SULFONATES
SWELLING
WATER
fuel cells
proton-exchange membrane
solvation
diffusion coefficient
molecular dynamics simulation
Environmental Molecular Sciences Laboratory