E. Ya. Davydov

Influence of Filler on Kinetics at Low-Temperature Conversion of Macroradicals

Abstract In poly(methyl methacrylate) and polyvinylpirrolydone the influence of aerosil on the kinetics of macroradical transformation at 120–220 K is established. The effect of filler is explained by the changes of the structural–physical properties of the polymer binder transformed into the interface state. From the kinetic data the effective thickness of interfaces is estimated.

Influence of Structure-Physical Properties of Polymer Matrix on Kinetics of Inside Cell Radical Reactions

Abstract In polymethylmethacrylate and cellulose acetate the kinetics of triplet cyclohexadienone carbenes decay by 77–135 K including a hydrogen atom transfer from C[sbnd]H bonds of macromolecules with the radical pair formation was examined. The kinetics of this process reflects the influence of peculiarities on a level of cells. The influence of external magnetic field on the decay of carbenes was established. The character of the magnetic is different in two polymers. Its determined by the cell recombination efficiency of radicals and the exchanged energy in radical pairs depending on mutual radical configurations. The structure-physical modification of polymers by aerosil filling connected with the formation of interfaces influences strong on the rate of carbenes conversions.

Effect of Polymer Matrix on Kinetics and Mechanism of Carbene Reactions

The features of kinetics and mechanism of the cage radical reactions initiated by carbenes in solid polymers has been considered. The peculiar low temperature reaction of arylcarbenes is their interaction in clusters with formation of biradicals (BR). The yield of BR is a measure of the distribution non-homogeneity of the carbene precursors in polymers. The reaction of BR formation allows us to study the molecular dynamics at cryogenic temperatures. The main factor determining the kinetic non-equivalence of triplet carbenes in low temperature reaction of the hydrogen atom abstraction is the dispersion of the cage distances between carbenes and C-H bonds of macromolecules. The strong effect of structural modifications in filled polymers on the thermal decay of carbenes has been established. The matrix effect on the mechanism of the product formation in the carbene reactions, associated with the relaxation processes, has been recognized by the example of the polyvinylalcohol cross-linkage. The advantage of polyisoprene stabilization against thermoxidation by the phenol grafting in carbene synthesis has been shown.

Kinetics and Mechanism of Liquid-Phase Nitration of 2, 4, 6-Tri-t-Butylphenol

Abstract Rates of reaction of 2,4,6-Tri-t-butylphenol with nitrogen dioxide (1000 ppm) have been determined in a batch reactor. The kinetics of reaction has qualitative distinctions according to the initial phenol concentration in the hexadecane solution. The phenol decay proceeds with fixed rate in time depending on the flow rate of NO2 at [PhOH]0 = 4.0·10 At[PhOH]0 = 6.0·10−5M the kinetics is controlled by the first order law. The rate constant of the phenolic hydrogen atom abstraction by NO2 is k1 = 5.9·-103 exp (-10kJ/RT), M−1s−1. At 22°C the rate constant of NO2 and phenoxy radical recombination is 76.5 M−1s−1. The formation of the reaction products has been studied by UV spectroscopy. The mechanism of nitration and side reactions in a batch reactor has been discussed.

Dynamics of Biradicals Formation by Low Temperature Conversions of Carbenes in Polymers

Abstract The kinetics of diphenylcarbene (DPC) conversions in clusters with biradicals (BR) formation has been studied in polycarbonate (PC) and polymethylmethacrylate (PMMA) at 77–125 K. The portion of carbene precursor-diphenyldiazomethane (DDM) iocalized in micropores has been evaluated from concentration dependences of BR yield. The correlation of kinetic parameters of BR low temperature formation with molecular dynamic properties of spin probe has been observed in studied polymers. The structural modification of PC by aerosil filling effects on conversion kinetics of BR.

Interaction of cyclohexadienone carbene with piperylene oligomer

Conclusions1.In the photodecomposition of p-benzoquinonediazide in a frozen matrix of piperylene oligomer, the formation of triplet cyclohexadienone carbene has been registered by means of ESR, along with allyl radicals of the matrix and phenoxyl radicals in the isolated state and in the form of radical pairs.2.When the carbene interacts with the matrix, it is inserted at C-H bonds of the macromolecules.3.A tunneling mechanism of H atom transfer has been proposed in the reaction of the carbene with the matrix. Estimates of the height and width of the potential barrier of the reaction are given.

Mechanism of transformation of diphenylcarbene into an oligomer of piperylene

Conclusions1.Formation of diphenylcarbene (DPC) and the radical pairs which arise as a result of migration of an H atom from the tertiary C-H bonds of the macromolecules into the DPC was recorded during photodecomposition of diphenyldiazomethane into an oligomer of piperylene by EPR at 77‡K.2.The process of thermal quenching of DPC passes through a stage of formation of radical pairs and is caused by migration of an H atom from the macromolecules of the matrix to the DPC by a tunnel mechanism.3.The kinetic principles of thermal quenching of DPC were explained by the distribution of the distances between the carbenes and C-H bonds in the macromolecules. The characteristics of this distribution of distances were estimated.

Investigation by the ESR method of the nature of free radicals of cellobiose, induced by photoreduction of Fe3+ ions

1. The nature of the free radicals formed inβ-D-cellobiose in the photoreduction of ferric chloride was studied by the ESR method at 77°K. 2. The conversions of the primary radicals at increased temperatures were investigated, and processes of their isomerization and dehydration were detected.

Transformation of polycarbonate based on 1,1-di-(4-hydroxyphenyl)-1-phenylethane under the influence of light in the presence of ferric chloride

The photodecomposition of ferric chloride in a polycarbonate based on 1,1-di-(4-hydroxyphenyl)-1-phenylethane leads to cleavage of the macromolecule at the carbonate group and the formation of radicals presumably of the phenyl type, which are localized on the macrochains.

Study of free radical conversions of a polycarbonate based on 1,1-di-(4-hydroxyphenyl)cyclohexane (ilon) by the esr method

1. The interaction of ilon and chlorine atoms produced by the photoreduction of additions of ferric chloride, was investigated by the ESR method at 77°K. 2. Under the action of light, an impurity of ferric chloride may lead to destruction of the polymer with breakdown of the macromolecules at the carbonate groups and C-Ar bonds. 3. Chlorine atoms also strip H atoms from the cyclohexane ring of the macromolecule with the formation of substituted cyclohexyl radicals.