Transfer in Undiluted Monomer Evaluation of Parameters

Chain Transfer in Undiluted Monomer Evaluation of Parameters.—In the absence of solvent the second term vanishes, leaving 

This quadratic in Rp is of the form required by the data for styrene-benzoyl peroxide shown in Fig. 14. The first term, corresponding to the intercept, represents the creation of chain ends through transfer with monomer. It occurs to an extent which is independent of the polymerization rate. The second term corresponds to 1/2 according to Eq. (27) it represents the pairs of ends created at the initiation step. Its coefficient is given by the initial slope of the line in Fig. 14. The third term, which accounts for the curvature at higher rates, represents the contribution of chain transfer with benzoyl peroxide. This becomes more prominent at higher rates because of the larger amounts of the initiator which are present. The marked rise in the curves for 

Over the range in which the rate of polymerization is proportional to the square root of the initiator concentration, Rj, may be replaced in Eq. (36) with the coefficients of the terms being appropriately altered. The contributions of the various sources of chain ends in the polymerization of styrene with benzoyl peroxide at 60°C are shown in Fig. 15 as functions of the initiator concentration.The uppermost curve represents the total number of polymer molecules per unit, and the differences between successive curves represent the contributions of the separate processes indicated. 

The initial linear portion of the curve shown in Fig. 14 (see inset) is given by the equation 

by comparison with Eq. (36), evidently Cm = 0.60X10 , i.e., chain radicals at 60°C prefer to add monomer rather than undergo transfer with monomer by the factor (1/0.60) X10. Knowing the value of Cm, one may replot the quantity l/Xn CM)/Rp against Rp. The slope of the resulting linear plot is equal to the coefficient of the last term in Eq. (36). In this way, the complete expression 

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