Termination and other processes in the polymerization of p-methoxystyrene and 2,2-dideutero-p-methoxystyrene

The uncatalysed thermally initiated free radical bulk polymerization of ?-methoxystyrene and 2,2-dideutero-?-methoxystyrene (65% deuterated) have been studied at 80, 100 and 120°.Both the rate of polymerization and the degree of polymerization are increased by deuteration, as would be expected from the deuterium kinetic isotope effect if disproportionation plays a part in the radical termination process. The effect of deuteration is least at the highest temperature, but it is shown that this does not mean that the extent of disproportionation decreases with increasing temperature.From a comparison of the effect of deuteration on the polymerization rate with its effect on the degree of polymerization, it is concluded that the transfer constant to monomer is less for the deuterated material than for the undeuterated material. It is suggested that the transfer process probably involves the donation of a deuterium or hydrogen atom from the growing radical to the monomer.     

Direct photolysis of acetyl benzoyl peroxide and benzoyl peroxide

Conclusion The quantum yields were found for the photodissociation of the O-O bond for acyl peroxides (0.12–0.14). In the framework of our assumptions, the increase in with increasing peroxide concentration may be related to conversion of the triplet excimer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2815–2817, December, 1986.     

The interaction between polymerization initiators and inhibitors in solutions—II. The reaction between benzoyl peroxide and p-benzoquinone in concentrated solutions; Some observations on the induced decomposition of the peroxide

The reaction between benzoyl peroxide and p-benzoquinone in concentrated solutions in a wide variety of solvents has been investigated by isolation and identification of the reaction products. Despite the high efficiency of p-benzoquinone as a trap for benzoyloxy radicals, partial decarboxylation to phenyl radicals usually occurs. Complete suppression of decarboxylation is achieved only when p-benzoquinone is present at such a high concentration that it is effectively the solvent for the reaction.The benzoyloxy- and phenyl semiquinones show marked differences in reactivity, the former tend to combine to form dibenzoyloxy dibenzoquinone while disproportionation is favoured by the latter to form quinhydrone of monophenylbenzoquinone.At lower quinone ratio, the peroxide undergoes induced decomposition by phenyl radicals both in “reactive” and “unreactive” solvents. The induced decomposition involves the formation of radical intermediates which undergo disproportionation, but not intramolecular rearrangement, to form p-phenylbenzoyloxy radicals. The latter can be captured, before undergoing decarboxylation, by the benzoyloxysemiquinones formed in the reaction.A correlation between the electron donating property of a radical and its capability to induce the decomposition of the peroxide was developed.     

Rigorous approach to kinetic parameters: polymerization of styrene with benzoyl peroxide in carbon tetrachloride

Both the rate constant of initiator dissociation, k_d, and the chain transfer constant, C_x, are determined by monitoring the rates of monomer and transfer agent conversions in a chain polymerization. Statistical analysis that takes into account the errors of experimental variables has been used to treat the kinetic data for the polymerization of styrene initiated by benzoyl peroxide (Bz₂O₂) in carbon tetrachloride at 60°C. Values of k_d and C_x produced by this error-in-variable method (EVM) are in accordance with those reported in literature. More important, the EVM algorithm always results in the smallest standard deviations of estimates, and hence, it is superior to the usual least-squares calculations. Other distinct features of the method are outlined. The initiator efficiency for Bz₂O₂ is estimated to be 0.72 under the present conditions.     

Determination of rate constants of benzoyl peroxide and azobisisobutyronitrile dissociation via polymerization kinetics

A linear expression is derived from Tobolsky's equation related to the dead-end polymerization method to determine the rate constant for the initiator dissociation. This novel graphical method applies remarkably well to the kinetic data collected by dilatometry from the polymerization of methyl methacrylate initiated by 2,2′-azobisisobutyronitrile and benzoyl peroxide in toluene at 60°C. Results obtained for these two initiators are consistent with those published in the literature. Applicability of the method is confined to at least 5% and at most 13% decomposition of initiator. However, these limiting values are sensitive to the experimental techniques employed. The effects of induced decomposition of benzoyl peroxide and thermal polymerization of methyl methacrylate are shown to be negligible in the present investigations.     

Catalytic oxidation of catechins to p-benzoquinones with hydrogen peroxide/methyltrioxorhenium

New p-benzoquinones were obtained by oxidation of catechin and epicatechin derivatives with the hydrogen peroxide/methyltrioxorhenium catalytic system. Reactions were carried out both in homogeneous and heterogeneous conditions and proceeded with high conversion and moderate yields. Polymer-supported methyltrioxorhenium systems were used as heterogeneous catalysts. After the first oxidation, the catalytic systems can be recovered and reused for five consecutive times without loss of stability and efficiency.     

Free radicals in benzoyl peroxide/amine initiating system

In an ESR study of donor-acceptor pairs consisting of benzoyl peroxide and tetramethyl-p-phenylenediamine or 2,4,6-tri-tert-butylaniline, two radicals were detected — the cation radical of tetramethyl-p-phenylenediamine and the 2,4,6-tri-tert-butylaminyl radical. As in Russian original; this term is used throughout article, but is probably a misprint for tert-butylanilinyl — Translator. Branch of the M. V. Lomonosov Moscow State University in the city of Ul’yanovsk, 42L Tolstoy Street, Ul’yanovsk 432700, Russia. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 88–90, March–April, 1997.     

Non-ideality in vinyl polymerization—VI: Polymerization of methyl methacrylate initiated by benzoyl peroxide

The polymerization of methyl methacrylate in benzene was initiated by benzoyl peroxide and examined by kinetic analysis particularly from the point of view of primary radical termination. It is concluded that the velocity constant for dissociation of the benzoyloxy radical to give the phenyl radical is affected by the nature of the medium.     

Reactions of methyl radicals with polymers—part 1: Abstraction reactions with poly(p-methoxystyrene)

The kinetics of hydrogen abstraction by methyl radicals from poly(p-methoxystyrene) have been investigated, methyl radicals being produced by the photolysis (λ = 254 nm) of the polymer under high vacuum. A new differential equation has been derived to describe simultaneous diffusion and reaction of methyl radicals; its solution, along with experimentally determined yields of methane, have been used to obtain a value for the rate constant for H abstraction from the polymer. The value of this constant is compared with previous data for poly(styrene) and the apparent agreement is found to be fortuitous. Relative to similar gas phase abstractions, the rate constants are lower by about four orders of magnitude; some of the factors contributing to this difference are discussed.     

Non-ideal kinetics in vinyl polymerization: Note on primary radical termination in benzoyl peroxide initiated polymerization of vinyl chloride in dichloroethane

The kinetics of vinyl chloride polymerization initiated by benzoyl peroxide doubly labelled with ¹⁴C and 'H were studied in 1,2-dichloroethane solution at 60°. The importance of primary radical termination in the polymerization is examined by kinetic analysis and by analysis of polymers for combined initiator fragments.     

Reaction of benzoyl peroxide with n-butyl orthotitanate

Conclusions n-Butyl orthotitanate (BT) reacts with a stoichiometric amount of benzoyl peroxide (BP) to form complexes of composition [3BT·BP] and [BT·BP]. The fastest decomposition of BP proceeds via the [3BT-BP] complex, i. e., with an excess of BT relative to BP. Butoxyl radicals are formed during the decomposition of the complexes. The end product when BP is decomposed by BT is di-n-butoxytitanium dibenzoate, which does not accelerate the decomposition of BP.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 714–717, March, 1978.     

Ferrocene polymers. synthesis and polymerization of p-ferocenecenylphenylacetylene

To investigate the influence of the ferrocenyl residue on the reactivity of phenylacetylene towards polymerization and on the properties of polyphenylacetylene, p-ferrocenylphenylacetylene has been synthesised and then polymerized with initiation by free radicals. Theoretical studies on the reactivity of p-ferrocenylphenylacetylene showed good agreement with the observation that the reactivity of this monomer is lower when compared to that of ferrocenylacetylene. The polymers synthesised showed good thermal stability