LIVING POLYMERIZATION REACTORS - PART III - TOWARDS MOLECULAR-WEIGHT DISTRIBUTION CONTROL IN A CSTR THROUGH PERIODIC FEED PERTURBATIONS

A novel algorithm has been described for the fast calculation of compl ex molecular weight distributions (MWD) produced in living anionic pol ymerisation conducted in periodically perturbed continuous stirred lan k reactor (CSTR), the predictions of which have been tested experiment ally using a limited set of conditions in a computer controlled labora tory-scale polymerisation reactor (Part I and II: Gosden et al., 1995a and 1997a). In this work, the prospect of using the algorithm for the control of flow reactors is explored giving particular attention to t he square-pulse feed strategies and reaction mechanism which have been used previously to demonstrate the influence of reactor feed conditio ns on polymer molecular weight distribution. Both initiator and monome r pulsed feeds are examined the main variables being pulse width, puls e period, the phase of initiator pulse relative to monomer pulse, mean residence time, average feed concentration of monomer and initiator, and the rate constants of initiation and propagation. The influence of these factors on the average molecular weight, molecular weight distr ibution and dispersity index of the product is considered. The use of pulsed feeds to a CSTR for tailoring polymer molecular weight distribu tion are briefly considered as are the ways in which the algorithm may be extended to other polymerisation chemistries, notably to pulsed la ser free-radically initiated polymerisation (PLP) processes.