Dipole relaxation and proton transport in polycrystalline γ-cyclodextrin hydrate: A dielectric spectroscopy study

摘要: Abstract The polycrystalline γ-cyclodextrin hydrate (γ-CD·12.2H 2 O) has been investigated via dielectric spectroscopy over a frequency range of 0–100 kHz and the temperature ranges 108.0–298.5 K (cooling) 109.0–433.0 K (heating). At T trans  = 186.7 K) reappears upon heating (  = 194.5 K).  > 250.0 K, permittivity e ′ loss ″ increase abruptly due to proton dc-conductance γ-CD·12.2H O which interpreted in terms theoretical model (Pnevmatikos, 1988) being consistent with generation ionic defects their combination dipole reorientations collective motion soliton-type. influence simultaneous dehydration process on this charge transport mechanism relies very sensitive balance between diffusive water molecules (exchange symmetry related positions) removal from crystal lattice. Arrhenius semiconductive behavior ac-conductivity 257.1–313.2 K E  = 0.42 eV) 331.2–385.1 K  = 0.39 eV) implies dominance diffusion conserves structural integrity endless hydrogen-bonded chains transfer along them. limited decrease 313.2 331.2 K its rapid above 385.1 K, indicates that rules out motion. Cole–Cole diagrams vs. ′) make clear during grain boundary polarization gradually becomes more significant than interior one. In 348.0–385.1 K, constrictive resistances are totally eliminated allowing extensive through grains specimen.