Nafion acid, dynamic mechanical

Partially Neutralized Nafion-Cs. Dynamic mechanical studies of partially neutralized Nafion-Cs from the Nafion acid was performed by Kyu et al (58). The starting material used in their study was Nafion acid of equivalent weight 1155. The acid samples were first boiled in distilled water to ensure extensive swelling, and then Immersed in... 

Tant et al. reported a dynamic mechanical transition of around 100 °C (maximum in G") for acid form Nafion having 1140 EW. o Since this transition also appeared for the sulfonyl fluoride precursor, but at a much lower temperature ( 0 °C), they concluded that it involved main chain motions that are restricted by the conversion to the acid form. These motions were further restricted by the conversion to the Na " sulfonate form owing to strong ionic associations between the side chains. In contrast with the work of Kyu and Eisenberg, no transition appeared at 0 °C in addition to that at 100 °C. While the equivalent weights of the samples utilized by Eisenberg and Kyu and Tant et al. were not quite the same, the notable difference in matrix Tg assignment is cause for confusion. 

Miura and Yoshida noted a dynamic mechanical tan (5 peak at 120 °C at 1 Hz, labeled a, for dry 1100 EW acid form Nafion. These investigators assigned this transition to motions within the polar clusters because it was sensitive to cation type. 

Cable and Moore performed DMA (dynamic mechanical analysis) studies of various Nafion membranes including the acid form. ° A tan <3 peak with maximum at 110 °C, referred to as Tg , was seen, and there is a suggestion of a shoulder on the low temperature side that might arise from another mechanism. As this membrane was dried at only 60 °C, the possibility of residual water incorporation exists. Moore and Cable concluded that the a relaxation was due to chain motions within and/or near the ion-rich domains and that the ji relaxation was... 

---