ESR and NMR study of the γ‐ray‐induced postpolymerization of vinyl monomers adsorbed on zeolite

Abstract

The γ‐ray‐induced postpolymerization of acrylonitrile and methyl methacrylate adsorbed on Linde zeolite 13X irradiated at 77°K has been studied between 303 and 343°K as a function of the amount of adsorbed monomer and of the irradiation dose. The change in the nature and the concentration of free radical with temperature and duration of the postpolymerization was followed by the ESR method, whereas the formation of polymer was monitored continuously by the decay of the 1H‐NMR absorption line of the monomer under high‐resolution conditions. It was found that the overall postpolymerization kinetics may be accounted for by assuming an exponential decay of radical propagation and recombination reactions with chain length. The tacticity of the polymer recovered by destroying the matrix in hydrofluoric acid was determined by 13C‐NMR. The probability of isotactic addition of AN and MMA is larger than in the radical polymerization in solution owing likely to the association of adsorbed monomer molecules in pairs preforming an isotactic diad.

Stereospecific Living Radical Polymerization: Dual Control of Chain Length and Tacticity for Precision Polymer Synthesis

“…[181][182][183] For tacticity of the polymers obtained from the absorbed monomers, γ-ray-induced polymerizations of AN and MMA adsorbed on Linde zeolite 13X were studied as a function of the amount of adsorbed monomer and the irradiation dose. 184 For tacticity of poly-(AN) and poly(MMA), which could be recovered by destroying the host matrix in hydrofluoric acid, isotactic specificities were higher than those obtained in solution (mm/ mr/rr ) 25/48/28 for MMA and 39/46/15 for AN, respectively). These were most likely because the adsorbed monomer molecules preformed an isotactic diad placement.…”

“…As in the inclusion polymerization in the organic clathrate compounds, radical polymerizations in porous inorganic materials with a larger channel have also been studied. The early studies had focused on the graft polymerization onto the inorganic substance, on which the absorbed monomers underwent polymerization. − For tacticity of the polymers obtained from the absorbed monomers, γ-ray-induced polymerizations of AN and MMA adsorbed on Linde zeolite 13X were studied as a function of the amount of adsorbed monomer and the irradiation dose . For tacticity of poly(AN) and poly(MMA), which could be recovered by destroying the host matrix in hydrofluoric acid, isotactic specificities were higher than those obtained in solution ( mm / mr / rr = 25/48/28 for MMA and 39/46/15 for AN, respectively).…”

Controlled polymerizations with constrained geometries

“…Historically, radical polymerization of polar vinyl monomers has most extensively been studied with microporous zeolites, by focusing attention on (1) possible elongation effects on the lifetime of growing radicals 51 and (2) possible steric effects on the chain growth step. 52 Recently, microporous zeolites have been used as catalyst supports for the polymerization of olefins, in which, however, spatial effects of the microporous cavities are not very clear. For example, in the polymerization of ethylene with supported zirconocenes by microporous zeolites, coupled with methylalumoxane (MAO) as cocatalyst, the activity is not related to the internal surface area of the zeolite, but the external surface area and the content of aluminium in the silicate framework appear to be more important.…”

Monomer- and polymer radicals of vinyl compounds: EPR and DFT studies of geometric and electronic structures in the adsorbed state

“…Electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) studies of radiation induced postpolymerization of acronitrile (AN) and methyl methacrylate (MMA) adsorbed on zeolite 13X show that overall postpolymerization kinetics may be accounted for by assuming an exponential decay of radical propagation and recombination reactions [13]. Studies of methylacetylene (MA) gas reaction in acid forms of the mordenite, omega, L, Y, beta, ZSM-5 and SAPO-5 molecular sieves indicate that MA reacts with acid sites of zeolites and forms large, conjugated polymeric species within the zeolites channels [14].…”