Segmental Dynamics in a Glassy Polyelectrolyte: Solid‐State ²H‐NMR

The segmental dynamics of a special “ionene” polyelectrolyte, poly[(dimethylimino)decamethylene‐tetra‐fluoroborate]‐[–(CH 2 ) 10 –N + (CH 3 ) 2 –] n *BF 4 − , has been investigated by applying one‐and two‐dimensional deuteron NMR techniques. Selective deuteration in the methyl groups and in the α‐, β‐ and γ‐positions of the methylene chain allow for investigation of the molecular mobility of each site. Below the glass transition the ammonium groups are essentially static, due to strong Coulombic interactions between the cationic centres, whereas the methylene chains undergo trans‐gauche isomerizations. At T g the ammonium groups become mobile, and we discuss the coupling of this glass transition process to the local methylene dynamics.