Retardation resulting from encapsulation of catalyst by insoluble polymer

5 Retardation resulting from encapsulation of catalyst by insoluble polymer 

The growth of insoluble polymer around catalyst particles forms a barrier through which monomer must diffuse and, if this is slow in comparison with reaction, a gradient of monomer concentration will be established with a progressive fall in rate to a steady value. 

Allen and Gill [154] considered the effect of this on change of polymerization rate with time for two models distinguished by either a steady concentration of monomer in the polymer layer or by a falling concentration of monomer through the polymer coating, viz. 

With the first model the rate declines from the normal unobstructed rate to a steady rate when the particles are completely covered, viz. 

With the diffusion controlled model it was deduced that the rate of polymerization per particle was given by 

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