Neutron time-of-flight data of polybutadiene and polyisoprene in a wide temperature range around the glass transition are reported. The anharmonic part of the spectra is evaluated using a recently developed time domain Fourier transform technique. The results corroborate the recent finding of two different time domains in the dynamics, one above a crossover time of about 2 ps and the other below it. Two different interpretations of the short time behavior are considered, namely a fast Debye regime of the α relaxation and a vibrational softening of the boson peak.

Studying the dynamic structure factor of polybutadiene in the first valley of S(Q) we observed a decoupling of microscopic and macroscopic time scales about 40° above ${\mathit{T}}_{\mathit{g}}$. At higher temperatures the time scale set by the viscosity scales with the microscopic scale, while at lower T strong decoupling effects occur. We present evidence that the decoupled low-temperature relaxation is distinctly different from the high-frequency ‘‘β process.’’ The decoupling temperature coincides with the critical temperature of the mode coupling theory.

The dynamics of water between highly oriented multilayers of 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC) has been studied in two time domains at different hydration levels. Incoherent quasielastic neutron scattering (QENS) and deuterium‐nuclear magnetic resonance (NMR) longitudinal (T₁) relaxation were employed to investigate both the high‐frequency motions of water (10⁻⁹–10⁻¹¹ s time scale) and their anisotropy, while 2H‐NMR transverse (T₂) relaxation was used for obtaining information on low frequency dynamical processes (microsecond time scale). Our results show that high frequency dynamics (picosecond‐time scale) at low hydration (three to four water molecules per lipid) can be understood solely as a uniaxial rotation of the water molecules tightly bound to DPPC head groups with a correlation time τ_rot≊62 ps at 55 °C and a rotational radius of 1±0.1 Å, but with no detectable translational degrees of freedom. The 2H‐NMR T₁ data (nanosecond‐time scale) can be explained satisfactorily on the basis of fast rotations with the correlation time above and a slower reorientation of the rotational axis (correlation time τ₁≊6 ns). Both QENS and 2H‐NMR T₁ measurements provide an apparent activation energy of E_a=32±1.0 kJ/mol for this process. Increasing the hydration level of the multilayers leaves the rotational motion essentially unchanged, but enables additional translational motion which can be considered as a jump diffusion process (diffusion coefficient D=16±1×10⁻¹⁰ m²/s at 44 °C and a mean residence time of τ₀=2.0±0.5 ps) of nonbound water. It is interesting to note that this diffusion is completely isotropic on the characteristic length scale of this QENS experiment (≤10 Å). Temperature variation shows that the phase state of the lipids has no significant effect on the high frequency dynamics of the water molecules. Measurements of the 2H‐NMR quadrupolar splitting of water (D₂O) at temperatures around the phase transition temperature T_m of the oriented DPPC multilayers clearly show a coexistence of the crystalline L_β