Non-ideal radical polymerization

When the assumptions under which relations (23), (28), (31) and (35) have been derived are not fulfilled, these relations are no longer valid. This is manifested by a change in the reaction orders with respect to initiator and to monomer with changing concentration of these components. One of the most general causes of deviations from ideality is termination by primary radicals. 

Deb and Gaba [14] studied the polymerization of styrene with diben-zoylperoxide and 2,2 -azobisisobutyronitrile. When deriving the kinetic relations, they considered mutual combination of primary radicals (and of their 

Substituting for [R ] and [1R ] from eqns. (47) and (48) into eqn. (49), they obtained the equation 

This equation is too complicated to be confronted with experimental results. It can be greatly simplified when reaction (46) is neglected. The assumption about the small importance of macroradical termination by phenyl radicals appears acceptable. First of all, the concentration of phenyl radicals is much smaller than that of benzoyloxyl radicals, kt pr should not substantially differ from kt pr, and finally the reactive phenyl radical should be immediately consumed by initiation. Equation (51) then assumes the form 

The expression for u [eqn. (53)] indicates how important it is to consider primary radical dissociation [the term 1fed/(ki[M])] when correct values of kt pr/fkjkp) are to be obtained, even when termination of macroradicals by secondary phenyl radicals is neglected. In Fig. 6, a graphical representation of eqn. (55) for styrene polymerization with dibenzoylperoxide in benzene is shown. When this dependence is measured for two monomer concentrations, fct pr/(kikp) and kj/kj can be calculated from the slope u. To reduce error, 

The expression for u [eqn. (53)] indicates how important it is to consider primary radical dissociation [the term fcd/( i[ ])] when correct values of pr/( i p) obtained, even when termination of macroradicals by 

Sets of rate constants for non-ideal styrene polymerization in benzene with dibenzoylperoxide initiation at 333 K [14], 

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