Donor-Acceptor Molecular Complexes in Alternating Copolymerization and in the Polymerization of Metal Halide-Complexed Vinyl Monomers

Abstract

Polar monomers containing pendant nitrile or carbonyl groups complex with Lewis acids with a resultant increasein their electron-accepting ability relative to that of the uncomplexed monomer. Complexed monomer participates in a one-electron transfer reaction with uncomplexed monomer or another electron donor monomer-e.g., olefin or conjugated diene-to form a charge transfer complex, which is a dipolar, diradical species analogous to the proposed intermediate in certain Diels-Alder reactions. The charge transfer complex may open spontaneously-e.g., olefin-acrylonitrile-alkylaluminum halide, styrene-methyl methacrylatealkylaluminum halide, isoprene-acrylonitrile-zinc chloride -or under the influence of free radicals-e.g., olefin-or allyl monomer-acrylonitrile-zinc chloride. The process involves spontaneous or radical-initiated homopolymerization of a Lewis acid activated, diradical charge transfer complex.'T^he free radical initiated polymerization of polar monomers containing -** pendant nitrile and carbonyl groups-e.g., acrylonitrile and methyl methacrylate-in the presence of metal halides such as zinc chloride and aluminum chloride, is characterized by increased rates of polymerization (2,3,4,5,10,30,31,32,33,34,53,55,65,66,75,76,77,87). Imoto and Otsu (30,33,34) have attributed this effect to the formation of a complex between the polar group and the metal halide. The enhanced reactivity of the complexed monomer extends to copolymerization with uncomplexed monomers, such as vinylidene chloride, which are readily responsive to 94 Downloaded by UNIV OF CALIFORNIA SAN DIEGO on August 21, 2015 |

Quantitative Theory of Free-Radical Copolymerization Allowing for the Phenomenon of Preferential Sorption

“…The second model implies the formation of a complex between the components of the polymerization mixture and their involvement in subsequent polymerizations. Kinetic equations based on this second approach consider all possible reactions between the growing macroradicals, the complexes and the monomers, as well as the effect of the solvent. − …”

“…Kinetic equations based on this second approach consider all possible reactions between the growing macroradicals, the complexes and the monomers, as well as the effect of the solvent. [7][8][9][10][11] Both theories pay almost exclusive attention to the kinetics and mechanism of the propagation step without considering the important role played by physical factors. Proper consideration of the latter has been introduced only recently.…”