Diffusion-controlled copolymerization kinetics

The Smoluchowski equation is used to derive equations for predicting the values of diffusion-controlled propagation and termination rate coeffs. in copolymn. None of the resulting expressions are any more complicated than the analogous homopolymn. results. Diffusion-controlled propagation rate coeffs. in copolymn. are predicted to depend only very weakly on chain-end type, and thus the propagation kinetics of high-conversion copolymns. are expected to be considerably simpler than those of low conversions. In considering termination, expressions for the rate coeff. for termination by reaction diffusion are first derived. It is possible that under some conditions (for example, high conversions) these expressions describe the overall rate of termination, but in general, overall rates of termination will be detd. by rates of center-of-mass diffusion, which are chain-length dependent. For this reason, the reaction-diffusion results are incorporated into a more general treatment of termination in which chain-end motion is both by translational and reaction diffusion; this treatment is envisaged as applying from intermediate conversions onward. Considerable effort is subsequently invested in developing simple descriptions of copolymn. in which rate coeffs. (and in particular those for termination) are allowed to be chain-length dependent. An important feature of application is that for every parameter utilized, a means of assocg. to it a value appropriate for a real system is discussed; in most cases this assocn. is readily carried out. [on SciFinder (R)]