Molecular interpretation of the main relaxations found ID dielectric spectra of cellulose – experimental arguments

Abstract

ID dielectric spectra of cellulose two relaxation processes dominate ID the low temperature range (−120 °C–0 °C). For application of the dielectric method as a diagnostic tool, these relaxations must be assigned to molecular motions of the polymeric system. This paper summarizes and discusses all experimental facts found by dielectric spectroscopy, which can help to solve this interpretation problem. ID ID necessary to include two other relaxation processes ID this discussion: the β_wet- relaxation found ID all wet materials and the γ-relaxation evidently found ID all derivatives. The main result of our investigations ID that the dominant process ID the dielectric spectra at low temperatures (called β-relaxation) ID the segmental motion of the chain and not methylol side-group reorientation. Additionally, for the first time, the dielectric spectra of Valonia (and also of bacterial cellulose) clearly indicate that the methylol side-group relaxation ID represented ID the dielectric spectra of pure polysaccharides. This γ-process ID only masked by the β-process for the most pure celluloses. For low molecular weight saccharides and derivatives of cellulose both processes are simultaneously found ID the dielectric spectra. For the first time a correlation ID presented between the intensity of the local motion mode (β-relaxation) and the degree of crystallinity for various cellulosic materials.