133Cs NMR investigation of anisotropic block copolymers

Anisotropic polyamide-polyether block copolymers doped with several cesium salts were studied with Cs-133 NMR. These materials;are highly hydrophilic. In the first set of experiments the evolution of the spectra was measured as a function of the swelling ratio in H2O/D2O mixtures. The evolution of the spectral parameters (Cs-133 chemical shifts and the quadrupolar splittings of Cs-133 and H-2) indicates that strong interactions exist between the Csf ions and the polymeric chains. At high swelling ratios the cations freely probe the anisotropic property of the polyether chains. In a second set of experiments dried materials were studied as a function of the sample temperature. Surprisingly, a significant increase in the anisotropic character of the Csf reorientation was measured when the temperature was raised. The increase of the electric field gradient could be considered as a measurement of some "apparent ionic order", which would be related to the modification of the averaged cation complexation site and to the dynamics of these ions. These measurements may serve as a new approach to the investigation of the nature of ion-polymer interactions.