ON THE EVOLUTION OF RELAXATION PROCESSES DURING THE FORMATION OF A MACROMOLECULE

The dielectric relaxation spectra of a liquid undergoing chemical reactions to produce a macromolecule have been measured at different instants of reaction and in the GHz frequency range. As the reaction proceeds, a second and slower relaxation process separates out from a faster relaxation process. The rate of the faster process changes little but its strength decreases with increase in the molecular weight of the macromolecule. Quantitative information on these changes show that the negative feedback between chemical reactions and molecular diffusion, which is irreversible in nature, has the same consequences for the relaxation behaviour as supercooling of a molecular or polymeric liquid. This implies that for each macromolecular state characterized by its molecular weight, there is a corresponding state of its unreacted components at low temperatures with similar thermodynamic and kinetic properties. Under certain condition, the extent of chemical reaction can be determined from dielectric measurements at a single GHz frequency.