Experimental study of dielectric relaxation in supercooled alcohols and polyols

Abstract

The nature of dielectric relaxation has been studied in a number of alcohols and polyols in the frequency range 106–10-3 Hz and the temperature range 77–368 K. Differential scanning calorimetry measurements have also been carried out on all the systems. In all the cases, the main dielectric relaxation rates were found to be strictly non-Arrhenius in nature. In the monohydroxy alcohols studied here, viz. 1-propanol, 1-pentanol and 2-ethylhexan-1-ol, the main relaxation process in the dielectric measurements was found to be Debye down to the glass transition temperature. With increase in the number of —OH groups on the molecule, the main dielectric process (namely the α process) was found to become increasingly non-Debye. Our measurements indicate that the main dielectric relaxation process in alcohols is perhaps due to the flipping of the—OH group in the linear chains from one oxygen atom to the other during the several breaks and reforming of the intermolecular hydrogen bonds, as was proposed originally by Hassion and Cole. An attempt has been made to explain the non-Debye behaviour of the polyols in terms of the above mechanism. The nature of the other processes observed is also discussed in detail.