MOLECULAR-DYNAMICS IN GLASSY POLYELECTROLYTES - A NMR-STUDY

The segmental dynamics of a special "ionene" polyelectrolyte, poly[(dimethylimino) decamethylene-tetrafluoroborate] ([-CH2)10-N+(CH3)2-]n.nBF4-), have been investigated by applying one- and two-dimensional deuteron NMR techniques. Selective deuteration in the methyl groups and in the alpha-, beta- and gamma-positions of the alkyl chain allowed for investigation of the molecular mobility of each site. Due to strong Coulombic interactions between the cationic centres, the ammonium groups are essentially static below the glass transition, whereas the alkyl chains undergo trans-gauche isomerizations. At T(g) the ammonium groups become mobile, and we discuss here the coupling of this glass transition process to the local methylene unit dynamics.