Effects of substituted triphenyl phosphites on the radical polymerization of acrylonitrile

The radical polymerization of acrylonitrile in the presence of nuclear-substituted triphenyl phosphites (p-Cl, H, p-CH₃, p-OCH₃) initiated by α,α′-azobisisobutyronitrile at 50°C was investigated. It was found that the rate of polymerization decreased at low concentrations of phosphite, but after reaching a minimum the rate increased again with further increase in the phosphite concentration in the case of all substituted triphenyl phosphites. Formation of a weak complex between phosphite as donor and acrylonitrile as acceptor was confirmed from the change in chemical shifts of vinyl protons to higher magnetic fields on NMR spectroscopy. From the results of continuous variation method using NMR spectra, the complex was found to be of the 1:1 type. The effects of substituted triphenyl phosphite on the rate of polymerization and the chain-transfer reaction to substituted triphenyl phosphites are discussed on the basis of these results.     

Kinetic study of radical polymerization of acrylonitrile in the presence of triphenyl phosphite

In the presence of triphenyl phosphite (TPP), the radical polymerization of acrylonitrile (AN) with α,α′-azobisisobutyronitrile (AIBN) as the initiator was carried out at 50°C, and the effects of TPP on the polymerization were kinetically investigated. The rate of polymerization was found to be proportional to the first order of the AIBN concentration and the AN concentration, respectively, at all concentrations of TPP. However, the rate of polymerization was proportional to the reciprocal of the TPP concentration at low concentrations, but to the first order of the TPP concentration at high concentrations. On assuming two termination reactions, i.e., the usual unimolecular termination by occlusion of the polymer radical and a bimolecular termination between the propagating radical and TPP, and the formation of the weak n-π complex between AN and TPP which accelerates propagation step, the rate of polymerization and the degree of polymerization were kinetically discussed. The equations derived were in good agreement with the experimental results.     

Effects of trivalent phosphorus compounds on vinyl polymerizations. II. Photopolymerization of acrylonitrile in the presence of triphenylphosphite

It was found that acrylonitrile is polymerized by UV irradiation in the presence of triphenylphosphite under conditions where acrylonitrile alone does not polymerize. The rate of polymerization was found to be proportional to the monomer concentration, the phosphite concentration, and the light intensity. It was thought that a donor-acceptor complex formed between triphenylphosphite and acrylonitrile absorbs light and initiates the radical polymerization.     

Photopolymerization of acrylates in the presence of bipyridinium salts

The photopolymerization of acrylic monomers initiated by bipyridinium salts has been studied. It has been shown that active radicals are produced more efficiently in the presence of atmospheric oxygen than in vacuum. A scheme of the process including one-electron transfer involving oxygen has been proposed.     

Photopolymerization of methyl methacrylate in the presence of C-phenyl-N-tert-butylnitrone

The effect of C-phenyl-N-tert-butylnitrone as a source of nitroxyl radicals on the kinetic parameters of radical photopolymerization of methyl methacrylate and the molecular mass characteristics of the resulting polymer was studied. It was shown that the polymerization at 30°C in the presence of this additive proceeds without the gel effect, thus allowing poly(methyl methacrylate) synthesis with a narrower molecular-mass distribution than the additive-free process.     

Photopolymerization of vinyl monomers in the presence of chlorosilane compounds

The photopolymerization of vinyl monomers (methyl methacrylate and styrene) was investigated in the presence of chlorosilane compounds. It was found that these additives acted as photosensitizers. In the case of the photopolymerization of methyl methacrylate, the rate of polymerization was found to be proportional to the concentration of methyl methacrylate and to the square root of the chlorosilane concentration. The chain-transfer constants of these photosensitizers, SiCl₄, CH₃SiCl₃, (CH₃)₂SiCl₂, (CH₃)₃-SiCl, and (CH₃)₄Si, with ultraviolet irradiation were 25.6 × 10^?3, 18.4 × 10^?3, 17.5 × 10^?3, 14.4 × 10^?3 and 0.5 × 10^?3, respectively, for methyl methacrylate.     

Photopolymerization of methyl methacrylate in the presence of tertiary amines

The sensitization effect of tertiary amines on the photopolymerization of methyl methacrylate was studied. N,N-Dimethylbenzylamine, triethylamine, and N,N-dimethylaniline increased the rate of polymerization in this order, but pyridine did not show any effect. A free-radical mechanism was confirmed by the tacticity of polymer, the retarding effect of hydroquinone, and the copolymer composition with styrene. On the basis of the detailed kinetics of the sensitized polymerization and the ultraviolet spectra of the reaction mixtures, a sensitization mechanism is proposed, in which the excited monomer and the amine form a complex and generate an initiating radical.     

Polymerization of acrylonitrile in presence of tributylborine

Summary It was found that acrylonitrile polymerizes in presence of tributyiborine activated by the boron trifuloride ether complex.     

On acrylonitrile polymerization in the presence of zinc salts

Acrylonitrile polymerization photoinitiated at 365 nm by pyrene and/or azobisisobutyronitrile in the presence of zinc salts in N,N-dimethylformamide solution has been studied by the rotating sector method. It was found that the ratio of the rate constants for propagation and termination (k_p/k_t) increases on addition of zinc salts (chloride, nitrate, acetate). This increase was more pronounced for the azobisisobutyronitrile photoinitiated polymerization of acrylonitrile then for its pyrene photoinitiated polymerization. The results confirm the previously expressed view concerning the dual role of zinc chloride in initiation as well as in propagation steps of acrylonitrile polymerization photoinitiated by aromatic hydrocarbons.

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Thermal properties of post-consumer PET processed in presence of phosphites

Thermal properties of recycled triphenylphosphite (TPP) chain extended poly(ethylene terephthalate) (PET) was investigated. As the TPP concentration increases, both reaction residues and molecular mass increase affecting significantly the thermal properties and crystallization behavior of the material. The presence of TPP residues did not affect the crystalline melt temperature (T _m), but modified the glass transition temperature (T _g), the crystallization temperature on heating (T _hc) and the crystallization temperature on cooling (T _cc). In the samples submitted to extraction with acetone, the properties were influenced by molecular mass changes, probably due to the presence of some insoluble reaction residue. The thermal stability of the sample purified by extraction after chain extension was comparable to that of the non-extended sample when heating was carried out under nitrogen atmosphere.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis and structures of substituted triphenyl(phenylimino)phosphoranes

Three substituted triphenyl(phenylimino)phosphoranes, namely (4‐cyanophenylimino)triphenylphosphorane, C₂₅H₁₉N₂P, (I), (4‐nitrophenylimino)triphenylphosphorane, C₂₄H₁₉N₂O₂P, (II), and (3‐nitrophenylimino)triphenylphosphorane, C₂₄H₁₉N₂O₂P, (III), were synthesized as precursors for the preparation of substituted diphenylcarbodiimides. All three compounds display a supramolecular arrangement in which the substituted benzene rings are organized in an antiparallel fashion. The nitro group on the ring participates in C—H...O and O...π interactions, forming intermolecular dimers. Compound (III) shows disorder which involves the rotation of one of the phenyl rings of the triphenylphosphine group.     

Photopolymerization of (meth)acrylates in the presence of polyheteroarylenes

The free-radical photopolymerization of (meth)acrylates in the presence of a polyheteroarylene dissolved in a monomer has been studied. The kinetics of the radical polymerization of these monomers mediated by polyheteroarylene and the corresponding model compound has been investigated by differential scanning photocalorimetry and IR spectroscopy. Based on the experimental data, it is inferred that copolymers form due to chain transfer and/or chain termination to polyheteroarylene macromolecules. With the use of ESR spectroscopy, new radicals generated upon the addition of model polyheteroarylene compound to the initial solutions are discovered and characterized. The mechanism of the formation of copolymers is advanced.     

The palladium-catalysed reaction of butadiene with acetic acid in the presence of phosphites

The palladium-catalysed co-oligomerisation of butadiene with acetic acid in the presence of various phosphites has been studied. It has been found that the use of ortho-alkyl or ortho-aryl substituted triaryl phosphites as ligands enables almost quantitative yields of acetoxyoctadienes to be obtained. Furthermore a significant degree of control of isomer ratios can be achieved.