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We report on the first observation of the dynamics of correlated hydrogen switching among the six Slater D2PO4 configurations, induced by unpaired D3PO4 and DPO4 Takagi group diffusion in a deuteron glass Rb0.5(ND4)0.5D2PO4. The results obtained by two-dimensional (2D) 31P exchange NMR prove the validity of the Slater-Takagi ice rules and allow for the direct determination of the correlation time for the unpaired Takagi group visits to a given D2PO4 group.

In isotactic poly͑methyl methacrylate͒ ͑PMMA͒, we investigate the dynamics of the ester methyl groups by means of deuteron magnetic resonance ͑DMR͒ in a deuterated sample. We find that the motion of the CD 3 -group affects the deuteron spin-lattice relaxation as well as the DMR line shape in a characteristic way. Quadrupolar order spin lattice relaxation measurements between T ϭ291 K and Tϭ70 K reveal a broad temperature dependent probability distribution of autocorrelation times c for the 2 /3 reorientation. This broad distribution corresponds to a temperature independent Gaussian distribution of activation energies (E a ) with variance E a ϭ13.8Ϯ0.5 meV ͑1.33 kJ/mol͒. The line shape transition between Tϭ70 K and Tϭ23 K is explained with the freezing in of the methyl group reorientation. By comparing our results in an 88% isotactic sample with results obtained from a 50% syndiotactic, 30% atactic, and 20% isotactic sample of a previous investigation, we demonstrate the higher local order of the 88% isotactic sample, which corresponds to a ratio of 1.6 in the relative width E a /E a of the E a distribution. We show that different stereospecific forms of PMMA can be easily distinguished by the characteristics of their line shape transition between Tϭ70 K and Tϭ23 K.

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