TY - JOUR
T1 - Effect of Annealing on Structure and Diffusion in Hydrated Nafion Membranes
AU - Lyulin, Alexey V.
AU - Sengupta, Soumyadipta
AU - Varughese, Anna
AU - Komarov, Pavel
AU - Venkatnathan, Arun
PY - 2020/11/13
Y1 - 2020/11/13
N2 - The annealing of polymer electrolyte membranes is known to affect the membrane structure and proton conductivity. The observed changes depend drastically upon the annealing temperatures and cooling rates. In this study, we have performed a fully atomistic classical molecular dynamics simulation of hydrated Nafion at various hydration levels and annealing rates. The simulations show the compression of hydrophobic Nafion domains by larger water clusters, with a strong antiplasticization effect upon hydration, demonstrated by increasing the glass-transition temperature. The close-range proximity of sulfonate-sulfonate groups of Nafion pendant side chains remains unchanged with the simulated cooling rates. The water clusters in hydrated Nafion become more disconnected and larger in size with slower cooling rates/increased annealing time. This results in the decrease of water and hydronium diffusivity and the corresponding conductivity, thereby explaining qualitatively the experimental observations.
AB - The annealing of polymer electrolyte membranes is known to affect the membrane structure and proton conductivity. The observed changes depend drastically upon the annealing temperatures and cooling rates. In this study, we have performed a fully atomistic classical molecular dynamics simulation of hydrated Nafion at various hydration levels and annealing rates. The simulations show the compression of hydrophobic Nafion domains by larger water clusters, with a strong antiplasticization effect upon hydration, demonstrated by increasing the glass-transition temperature. The close-range proximity of sulfonate-sulfonate groups of Nafion pendant side chains remains unchanged with the simulated cooling rates. The water clusters in hydrated Nafion become more disconnected and larger in size with slower cooling rates/increased annealing time. This results in the decrease of water and hydronium diffusivity and the corresponding conductivity, thereby explaining qualitatively the experimental observations.
KW - aging
KW - glass transition
KW - molecular dynamics simulation
KW - Nafion
KW - polyelectrolyte membrane
UR - http://www.scopus.com/inward/record.url?scp=85097556879&partnerID=8YFLogxK
U2 - 10.1021/acsapm.0c00875
DO - 10.1021/acsapm.0c00875
M3 - Article
AN - SCOPUS:85097556879
VL - 2
SP - 5058
EP - 5066
JO - ACS Applied Polymer Materials
JF - ACS Applied Polymer Materials
SN - 2637-6105
IS - 11
ER -