KINETICS OF THE DISPERSION RING-OPENING POLYMERIZATION OF EPSILON-CAPROLACTONE INITIATED WITH DIETHYLALUMINUM ETHOXIDE

Dispersion polymerization of epsilon-caprolactone initiated with dieth ylaluminum alkoxide, carried out in the 1,4-dioxane:heptane (1:9 v/v) mixture at room temperature in the presence of poly(dodecyl acrylate)- g-poly(epsilon-caprolactone) used as the surface active agent, proceed s in two stages. In the first stage the growth of the poly(epsilon-cap rolactone) chains is initiated in solution and, when the molecular wei ght of growing macromolecules comes close to 1000, the primary particl es are nucleated and all propagating chains become incorporated into g rowing microspheres. In the second stage the polymerization process co nsists of propagation taking place inside microspheres into which mono mer molecules diffuse from solution. During the first stage the appare nt propagation rate constant is low and does not exceed 1 x 10(-2) L . mol(-1). s(-1). In the second stage, due to the high local concentrat ion of growing species confined in polymer particles, the apparent pro pagation rate constant becomes much higher. For monomer concentrations in the region from 3.9 x 10(-1) mol . L(-1) to 4.3 x 10(-1) mol . L(- 1) and for initiator concentrations ranging from 3.4 x 10(-3) mol . L( -1) to 2.6 x 10(-2) mol . L(-1) the apparent propagation rate constant (k(p)(app)) varied from 4.79 x 10(-1) L . mol(-1). s(-1) to 6.5 x 10( -2) L . mol(-1). s(-1).