Influence of the p-toluenesulphonylation of cellulose on the polymer dynamics investigated by dielectric spectroscopy

Cellulose p-toluenesulphonates (tosyl cellulose) were studied by dielectric spectroscopy. Two relaxation processes were observed for samples of low degrees of substitution (DS) in the low temperature range (−130 to 0 °C). These are related to the local chain and the tosyl substituent motion, β- and γ-relaxations, respectively. For DS values higher than 1.4, the dielectric spectra no longer could be separated into the individual processes, because the dielectric response became reduced in intensity and its distribution in the frequency scale was broadened by cross-correlation of different motions between the modes of the substituents and the segmental motions of the chain. Significantly, different local chain (β-relaxation) behaviour was found for derivatives of DS≈0.9 with block-like and random distribution of substituents along the backbone. The dynamic behaviour of the tosylated polymers is compared with other cellulose derivatives and revealed similar qualitative behaviour, but the type of the substituents at the anhydroglucose unit has a characteristic influence on the dynamic parameters of the relaxation time, the activation energy related and the shape parameter of the relaxation processes.