Rate coefficients for propagation

Granted the invariance of the rate coefficients for propagation, kp, and catalyst split-off, trm, the net rate of formation of an adduct Pj, with j + 1 monomer units is... 

Absolute rate coefficients for propagation via free anions (fep at 25 C (1 mole sec ) in the polymerization of styrene.)... 

If initiation is sufficiently rapid that it can be considered as complete prior to propagation, then the observed rate coefficient, fe, will approximate to the rate coefficient for propagation, fep. Thus considering data at time t = 0 yields the equation... 

Rate coefficients for propagation at 30 C, with molecular iodine as initiator [62-65]. 

Higashimura [7] has used a crude statistical thermodynamic approach to compare pre-exponential factors for free ion, free radical and ion pair propagation reactions. According to Eyring s theory the rate coefficient for propagation has the form... 

Application of these techniques and interpretations to the polymerization of THF by Et3 0 BF4 in methylene chloride at 0°C has yielded a value for the rate coefficient for propagation, fep, of 3.5 x 10 1 mole sec , which agrees closely with the results obtained by Tobolsky. The corresponding termination coefficient, fet, is 2 x 10 sec . When Etj O " AlCl was used as the initiator excessive termination was shown to... 

The detailed mechanism of oxidation of butane [35] is well accounted for by the same elementary steps as for isobutane but with two important differences. First, the rate coefficient for propagation at 100°C in n-butane is only 1/10 as large as for isobutane, as expected for abstraction of a sec-C—H bond stronger by 3.5 kcal mole"1 than the f-C—H bond. The second, more important, difference arises in the self-reaction of sec-R02 radicals, viz. 

The form of Eq. (47) is analogous to the homopolymerization rate expression [Eq. (10)], with a copolymer-averaged rate coefficient for propagation (generalized for a system with Nmon different monomers) defined in Eq. (50). 

In the case of copolymerization, the copolymer-averaged rate coefficient for propagation shonld be used instead of k and [A/]p represents the total monomer concentration in the polymer particles [11]. 

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