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SynopsisThe general kinetics of alternating inter-intramolecular propagation are presented and discussed. The major factor which determines the microstructure of the polymer, the relative rates of the intramolecular and intermolecular reactions is examined. From the general kinetics methods are proposed for the determination of the ratio of rate conatants for these reactions.[ml]/ [M3] = 1 + (kc/kll)(l/[Ml]o), where [ml] is the concentration of monomer units in the polymer, [M3] is the concentration of uncyclized units, [MI] is a parameter related to monomer concentration, k, is the rate constant for cyclization and k11 the rate constant for linear propagation. Other methods which may give information on the nature of the termination reaction are discussed.

The solution polymerization of methacrylic anhydride, a monomer which undergoes predominantly inter‐intramolecular propagation, shows kinetics similar to vinyl polymerization. The overall rate of polymerization is proportional to the square root of the initiator concentration and to the 3/2 power of the monomer concentration. The apparent, overall energy of activation was found to be 23.0 kcal./mole when azobisisobutyronitrile was used as the initiator. The value of Ep − Et/2 obtained is 8.0 kcal./mole. This compares with the value of Ep − Et/2 found for methacrylic acid in the same solvent (DMF) of 9.8 kcal./mole. Both values are in the range of values for other vinyl monomers. The polymer obtained from reactions carried out at monomer concentrations of 17% and lower were completely soluble, showed low amounts of residual unsaturation, and did not appear to be branching to a measureable extent. At higher monomer concentrations, gel was formed, and the polymers showed higher residual unsaturation levels. Poly(methacrylic anhydride) hydrolyzed to the polyacid did not show any enhancement in crystallinity over the polyacid prepared directly from methacrylic acid. Both show only low orders of crystalline content.

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A study has been carried out on the kinetics of the emulsion polymerization of 2,3‐dimethylbutadiene‐1,3. The kinetic treatment of Smith and Ewart was applied for the direct determination of the absolute propagation rate constant kp. The following expression was obtained: kp = 8.9 × 107 exp {−9000/RT} liter/mole/sec. A previously developed treatment was applied to the determination of the relative and absolute crosslinking rates of 2,3‐dimethylbutadiene‐1,3. The results led to the following expression for the absolute crosslinking rate constant kx: kx = 3.0 × 106 exp {−14400/RT} liter/mole/sec. A comparison of these rate constants was made for the three dienes, viz., butadiene, isoprene, and dimethylbutadiene. The propagation rate constants were found to vary only by a factor of 2–3. However, the crosslinking rates were found to decrease considerably in going from butadiene to isoprene to dimethylbutadiene. This was attributed, mainly, to the decreased side‐vinyl content of the latter two monomers, compared to butadiene, as well as to the steric hindrance imposed by the presence of the methyl group.