The dynamics of regioregulated poly͑4-methylthiazole-2,5-diyl͒ ͑HH-P4MeTz͒ was investigated by solidstate 1 H, 2 D, and 13 C NMR spectroscopies, and differential scanning calorimetry ͑DSC͒ measurements. DSC, 2 D quadrupolar echo NMR, 13 C cross-polarization and magic-angle spinning ͑CPMAS͒ NMR, and twodimensional spin-echo CPMAS NMR spectroscopy suggest existence of a quasiordered phase in which backbone twists take place with weakened stackings. Two-dimensional exchange 2 D NMR ͑2DEX͒ detected slow dynamics with a rate of an order of 10 2 Hz for the CD 3 group in d 3 -HH-P4MeTz at 288 K. The frequency dependence of proton longitudinal relaxation rate at 288 K shows a −1/2 dependence, which is due to the one-dimensional diffusionlike motion of backbone conformational modulation waves. The diffusion rate was estimated as 3 ± 2 GHz, which was approximately 10 7 times larger than that estimated by 2DEX NMR measurements. These results suggest that there exists anomalous dispersion of modulation waves in HH-P4MeTz. The one-dimensional group velocity of the wave packet is responsible for the behavior of proton longitudinal relaxation time. On the other hand, the 2DEX NMR is sensitive to the phase velocity of the nutation of methyl groups that is associated with backbone twists. From proton T 1 and T 2 measurements, the activation energy was estimated as 2.9 and 3.4 kcal/ mol, respectively. These were in agreement with 3.0 kcal/ mol determined by a Møller-Plesset molecular orbital calculation. We also performed a chemical shielding calculation of the methyl carbon in order to understand chemical shift tensor behavior, leading to the fact that a quasiordered phase coexists with the crystalline phase.

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