Cyclization in crosslinking polymerization. II. Chain polymerization of a bis unsaturated monomer (polydisperse case)

The procedure suggested for the description of ring‐chain competition in the polymerization of a bis unsaturated monomer derived in Part I for monodisperse primary chains was extended to include the case of polydisperse primary chains. The cyclization probability and differential fractions of units in the chain are regarded as different for each group of r‐mers. The composition of primary chains remains practically unchanged at r > 100, and the summations were therefore truncated at r = 100. Model calculations show that trends in the composition change of the polymer and of the gel point as a function of the degree of polymerization of primary chains, of the distribution width, and of dilution are in accord with experimental findings. Comparison with the data published on the polymerization of dialiyl phthalate (with a marked cyclization and short primary chains) has revealed that the model is generally satisfactory, but that it somewhat underestimates cyclization because of the neglected effect of cycles on the conformational statistics of chains, or the neglected effect of excluded volume. This is particularly reflected in a lower calculated conversion at the gel point. This underestimation may partially be compensated for by assuming a higher chain flexibility.