Investigation of relaxation processes and phase transition in the polyethylene glycol 400 using IR spectra in a wide temperature range

Abstract

We examined the amorphocrystalline structures of polyethylene glycol 400 (PEG-400) using thermogravimetric, calorimetric, X-ray phase analysis, dielectric and IR spectroscopies. The physical properties of such a system are affected by the presence of water, due to the formation of the hydration shell. When the amorphic-crystalline PEG-400 is heated, it undergoes first low-temperature and then high-temperature dielectric relaxation. We demonstrate that the low-temperature dielectric relaxation is due to conformational motion of the PEG molecule's HO-CH2-CH2- end groups. In contrast to that, the high-temperature relaxation is due to the conformational motion in the central parts of the PEG molecule, due to the motion of local topological defects along the backbone of the molecule.