When the potential of average force based on the excluded volume affects the relative motions of the polymer radicals, the specific rate for bimolecular reaction between them can be approximated as kt = const. (ns)−a, where a = 0.153(2b − 1), b being a constant in the Mark‐Houwink equation, and n and s being degrees of polymerization. Introduction of such a rate into kinetic equation yields a relative molecular weight distribution: G(n) = (n/m)2–2a exp {ph(m1–a − n1–a)}, where m = (2/ph)1/(1–a) is a degree of polymerization for the maximum in G(n) and ph is a parameter denoting kinetic character. Further, the relationship between polymerization rate Rp, monomer concentration [M], and initiator concentration [ε] is found to be: where σ is a parameter denoting primary radical termination and η and η⊖ are viscosities for an arbitrary solvent and ⊖‐solvent, respectively. These relationships are sufficiently applicable to the data obtained in the polymerizations of styrene and methyl methacrylate.

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The dependence of the polymerization rate on initiator concentration over a wide range of conversion is analyzed by an equation derived on the assumption that the primary radical termination is important and another equation derived on the assumption of the chain length dependence of the termination. The analytical result by the former equation, is nearly equivalent to the result by the later when transfer predominates. Fujita‐Doolittle theory is applicable to both results. In the apparent termination, small polymer radicals not exceeding the size of the segment play an important role.

SynopsisThe thermal decomposition and hydrolysis of 2,2'-azobis(2amidinopropane) were examined as functions of pH. The rate of decomposition decreased with increasing pH. The specific rates at 60°C were 3.85 X l/sec at. p H > 8.5. The hydrolysis in alkaline solution yielded 2,2'-azobis(Z-carbarnylpropane)which was stable to thermal decomposition. The relation between the specific rate of hydrolysis kh' and the concentration of hydroxyl ion was obtained as kh' = 4.0 X [OH]0.60 l/sec at 60°C. In alkaline solution, the rate of hydrolysis was considerably larger than that of thermal decomposition. A mechanism for t.his hydrolysis is propcsed. l/sec a t pH 0.90 and 2.5 X 's buffer solution (pH = 1.81-11.98) was prepared by using acetic acid, phosphoric acid, boric acid, and sodium hydroxide of reagent grades. The solution of pH 0.90 was prepared by adding reagent grade HCl solution to the pH 1.81 buffer solution.The author wishes to thank Wako Pure Chemical Industries for supplying AAP.2HC1.

In consideration of the modern idea of reptation, it is proposed that the rate of termination is proportional to n-112 (n =chain length) when n is less than a critical chain length nc, but the rate is proportional to n-2 when n > nc. The molecular weight in terms of the gel effect is calculated by using such a rate. This molecular weight fits sufficiently to the experimental molecular weight obtained previously in a radical polymerization of methyl methacrylate. Further, the rate constant of termination between small polymer radicals is discussed by the free volume theory.