MONOMER-MEDIATED RELAXATION IN LIVING POLYMERS

We study the relaxation kinetics in living polymer systems, such as po ly(alpha-methylstyrene), where association-dissociation processes are monomer mediated. so that the molecular weight distribution adapts rev ersibly to the new thermodynamic parameters by monomer exchange at act ive sites at chain ends. Using both a system of rate equations for the concentration of l-mers, which is solved numerically, and Monte Carlo simulations in terms of a bond fluctuation model. we find a good desc ription of the dynamic response of the system to large deviations from equilibrium in terms of a single relaxation tau(L) proportional to L- 5, where L is the average chain length in equilibrium. The response it self is found to decay with time t as t(-1) in the late stages of rela xation. In contrast to wormlike micelles with scission-recombination k inetics. the: average lifetime tau(l) of chains of length I is found t o be practically independent of I for l much greater than 1 for given rate of dissociation which map essentially determine the dynamics of s uch systems.