Molecular mass distribution of oligomers in products of tetrafluoroethylene radical telomerization

Kim, I. P.

doi:10.1007/s11172-013-0299-3

Cited by 2 publications

(2 citation statements)

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“…This structure of the oligomer solution was confirmed by quantum chemical calculations [4]. Studies of TFE polymerization in aprotic solvents (carbon tetra chloride) [9,10] showed that colloid and gel formation in these media occur in the same range of concentra tions, though they are dominated by weaker van der Waals interactions, but not by hydrogen bonds. It was found [3] that the phase separation time of a colloid solution in centrifugal fields depends non monotonically on the initial TFE concentration, which is not consistent with the model of precipitation of colloid particles with constant density and diameter and is more likely to resemble the viscoelastic phase separation.…”

Section: Introductionmentioning

confidence: 78%

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Radical polymerization of tetrafluoroethylene that forms a colloid solution and gel of oligomers

Kim

Benderskiĭ

2014

Russ. J. Phys. Chem.

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As the concentration of tetrafluoroethylene (TFE) in the solvent increases, its polymerization is shown to be accompanied by a transformation of the resulting homogeneous solution of oligomers into a col loid one, which then transforms into gel. The micron sized colloid particles consist of oligomers and solvent molecules, whose number per TFE unit in the oligomer decreases from 15-20 at the threshold of dense phase formation to 4-6 in a gel. A kinetic model of polymerization was suggested. In this model, the chain propa gation is limited by monomer diffusion to the growing macroradical and the chain transfer (oligomer forma tion and regeneration of the prime radical) is limited by the reaction of the growing macroradical with the solvent molecule. The model that allows for the decrease in the diffusion coefficients with increasing of the oligomer chain length and their local concentration leads to a spatially inhomogeneous molecular mass dis tribution, with long oligomers accumulated in the vicinity of the macroradical and short ones in the distant zone. The formation of colloid particles and gel occurs when the concentration of long oligomers shaped as rigid rods exceeds the critical value for the dense phase formation and the percolation threshold, respectively. The transition from the initial spatial distribution to the equilibrium distribution described by the phase dia gram was considered using the model of viscoelastic separation so that phases retain spatial continuity.

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Section: Introductionmentioning

confidence: 78%

“…A transition from one to two mode MMD was found at increased C for TFE poly merization in all solvents under study [9,10]. At low TFE concentrations, when the oligomer solutions remained homogeneous, the one mode MMD is described by Eq.…”

Section: (24)mentioning

confidence: 91%