Reactions at Polymer Interfaces: Transitions from Chemical to Diffusion-Control and Mixed Order Kinetics

We study reactions between end-functionalized chains at a polymer-polymer interface. For small chemical reactivities (the typical case) the number of diblocks formed, Rt, obeys 2nd order chemically controlled kinetics, Rt ∼ t, until interfacial saturation. For high reactivities (e.g. radicals) a transition occurs at short times to 2nd order diffusion-controlled kinetics, with Rt ∼ t/ ln t for unentangled chains while t/ ln t and t 1/2 regimes occur for entangled chains. Long time kinetics are 1st order and controlled by diffusion of the more dilute species to the interface: Rt ∼ t 1/4 for unentangled cases, while Rt ∼ t 1/4 and t regimes arise for entangled systems. The final 1st order regime is governed by center of gravity diffusion, Rt ∼ t .