The Fundamental Basis for Cyclopolymerization. V. A Kinetically Based Explanation for the Enhanced Rate

Abstract

Abstract The enhanced rate of cyclopolymerization of divinyl monomers over that of the corresponding monovinyl monomers is considered. The relative polymerization rates of the following monovinyl-divinyl monomer pairs were determined: methyl methacrylate-methacrylic anhydride; 2-cyano-l-heptene-2,6-dicyano-l, 6-heptadiene; and 2-phenyl-l -hepteneh-2,6-diphenyl-1,6-heptadiene. An attempt was made to prepare methacrylic isobutyric anhydride as the monovinyl monomer to compare with methacrylic anhydride but its inherent instability precluded its isolation in pure state. The over-all rate of the divinyl monomer in every case was considerably greater than that of the corresponding monovinyl monomer, the ratios varying from two to ten. From the rate data obtained it was possible to estimate the effective concentration of the intramolecular double bond with respect to the radical, and values greater than 20 M at 50° were obtained in the case of 2,6-dicyano-l,6-heptadiene. This value compares favorably with a concentration of 21.8 M for liquid ethylene at -102°. These results can be interpreted most satisfactorily in terms of a concerted cyclization step which requires considerable preorientation prior to reaction. This favorable preorientation could be interpreted as an electronic interaction between the developing radical cite and the intramolecular double bond.