Boris E Krisyuk - Academia.edu (original) (raw)
Papers by Boris E Krisyuk
European Polymer Journal
A promoting effect of tensile stress has been revealed for the rate of oxidation of high- and low... more A promoting effect of tensile stress has been revealed for the rate of oxidation of high- and low-density polyethylene and isotactic polypropylene films with ozone. The degree of oxidation and the presence of overstressed bonds on the sample surface were detected by infrared spectroscopy in transmitted and reflected light. Overstressed bonds on the surface were set up by using various quenching regimes and in the bulk by applying a load. The stress-induced changes in segmental mobility of macromolecules were studied by ESR spectroscopy using a stable nitroxyl radical-probe. Supramolecular structure of the samples was investigated by using birefringence, polarized infrared spectroscopy and X-ray diffraction methods. A substantial difference has been found between the stress and the strain dependences of the rate of oxidation of the polymer films with ozone.
It is known that the action of ozone on polymers results in the formation of free radicals. This ... more It is known that the action of ozone on polymers results in the formation of free radicals. This study involves the initiating capability of ozone in reaction with powdered isotactic polypropylene (PP). The chemical reactions are presented on graphs.
Journal of Molecular Structure: THEOCHEM, 2005
Journal of Polymer Science: Polymer Physics Edition, 1983
ABSTRACT Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high... more ABSTRACT Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high-density and low-density polyethylene, and isotactic polypropylene. Experiments have been performed on thin (up to 20 μm) uniaxially oriented films under constant stress σ, under conditions where the chemical kinetics rather than diffusion dominates. It is found that the oxidation rate is proportional to exp(′σ/RT) where ′ is an empirical constant. The effects of unimolecular chain scission and the change of molecular polymer parameters under stress on this dependence are negligible. An analogy with the kinetics of oxidation of stressed cycloparaffins by ozone is noted. A mechanism is suggested to explain the accelerating effect of tensile deformations on chemical processes involving rehybridization of carbon atoms in the main chain from the sp3 to the sp2 state. An ESR study with a stable nitroxyl radical probe revealed a change in the segmental mobility of polymer chains in the course of loading.
Russian Journal of Physical Chemistry B, 2010
The influence of strain in the reaction center containing a double bond on double bond reactivity... more The influence of strain in the reaction center containing a double bond on double bond reactivity at the first stage of the reaction with ozone was studied by the B3LYP density functional theory method and ab initio MP2, CCSD, QCISD, and MRMP2 multireference methods. The 6 31+G** and 6 311+G** basis sets were used. The reactions of ozone with ethylene and butylene were studied. Deformation (ε) was intro duced by using the C=C bond length or the distance between extreme carbon atoms as a coordinate not sub jected to optimization. Stretching of the double bond was found to activate the reaction by the mechanisms of symmetrical and nonsymmetrical addition. The sensitivities to deformation were similar in the two chan nels. When the butene fragment as a whole was stretched, a different picture was observed, and the reaction with ozone was decelerated. In both cases, the logarithms of rate constants linearly depended on ε. The cal culation results were analyzed using the approach developed earlier, which allowed the calculation results to be used to obtain an analytic form of the dependence of activation energy E a on the strength of bonds and to relate deformation induced changes in E a to the length and rigidity of the initial and transition states.
Russian Journal of Physical Chemistry B, 2010
The UQCISD, UB3LYP, UMP2, and MRMP2 methods in conjunction with the 6 31+G**/6 311+G** and aug cc... more The UQCISD, UB3LYP, UMP2, and MRMP2 methods in conjunction with the 6 31+G**/6 311+G** and aug cc PVDZ basis sets are used to study the primary reaction of ozone with chlorinated eth ylene derivatives: tetrachloroethylene, trichloroethylene, 1,2 trans dichloroethylene, 1,2 cis dichloroethyl ene, 1,1 dichloroethylene, and chloroethylene. The reaction is studied for both concerted and nonconcerted ozone addition. The UB3LYP DFT method in conjunction with the 6 31+G** basis set is used to examine various modes of addition of ozone to these chlorinated ethylenes by the Criegee and DeMore mechanisms. The geometry and energy of the transition states, the enthalpy and entropy, and the rate constants and ratios thereof for all the reactions are calculated. The UB3LYP method generally satisfactorily describes the two reaction pathways and, largely correctly predicts the rate constants, in agreement with the available experi mental data. At the same time, this method appears to be inapplicable to modeling the interaction of ozone with 1,1 dichloroethylene. In this case, the single determinant approximation turns out to be unsuitable, and, therefore, MCSCF methods should be used. The MRMP2 method yields reasonable values of the rate constants for the DeMore mechanism, whereas in the case of the Criegee mechanism, the MP2 method does well. The UB3LYP/6 31+G** and UQCISD/aug cc PVDZ methods give similar values of the ratio between the rate constants for the two pathways, a result that demonstrates the versatility of the first one.
Kinetics and Catalysis, 2015
ABSTRACT Quantum chemical calculations have been carried out for the ozonolysis of monofluoro-, m... more ABSTRACT Quantum chemical calculations have been carried out for the ozonolysis of monofluoro-, monochloro-, 1,1-difluoro-, and 1,1-dichloroethylene using the aug-cc-pVDZ basis set by the B2PLYP (B2LYP-D) double-hybrid method involving the Møller-Plesset perturbation theory, the CASSCF multiconfigurational ab initio method with MRMP2 corrections, and the CCSD coupled cluster method. The mechanisms of concerted (Criegee) and nonconcerted (DeMore) additions have been investigated. The CCSD method more precisely simulates these reactions. With the MRMP2 method, the overall reaction rate constant is underestimated because of incomplete geometry optimization, but on the whole the dependence of the rate constant on the nature and number of substituents is practically identical to the dependence predicted by the two other methods. Polar substituents in the molecule increase the contribution from the nonconcerted addition mechanism, which reaches 50% for 1,1-difluoroethylene and 98% for 1,1-dischloroethylene.
Russian Chemical Bulletin, 2004
The N—H bond dissociation energy (DNH) in the 4-anilinodiphenylaminyl radical formed from N,N&... more The N—H bond dissociation energy (DNH) in the 4-anilinodiphenylaminyl radical formed from N,N'-diphenyl-1,4-phenylenediamine was experimentally determined and calculated by the quantum-chemical method. The experimental DNH value was found from the enthalpy of the reaction of N,N'-diphenyl-1,4-benzoquinonediimine with 4-hydroxydiphenylamine taking into account the bond dissociation energies in 4-hydroxydiphenylamine and its aminyl and phenoxyl radicals, which were determined by the intersecting parabolas
Polymer Science U.S.S.R., 1987
ABSTRACT Rate constants of the spin exchange between nitroxide radicals and oxygen in oriented an... more ABSTRACT Rate constants of the spin exchange between nitroxide radicals and oxygen in oriented and isotropic samples of polypropylene, high density and low-density polyethylene were measured over the temperature range of 290–373 K by the method of continuous saturation of the EPR spectrum of the spin probe, and used to calculate oxygen permeability. The results agree with literature data for isotropic samples, but are smaller by 1·5 to 2·5 times upon orientation.
Polymer Science U.S.S.R., 1988
ABSTRACT The rate constant of the reaction of ozone with powdered polypropylene and with isotropi... more ABSTRACT The rate constant of the reaction of ozone with powdered polypropylene and with isotropic or oriented polypropylene films was determined over the temperature interval 300 to 370 K by measuring absorption of ozone. An acceptor of free radicals, (4,4′-dimethoxyphenyl nitroxide), was used to measure the rate of radical formation in polymer samples. The probability that the radical leaves the cage is 2·5-3% in isotropic and 4·5% in oriented polypropylene at 333 K. The results are discussed in terms of anisotropic microdiffusion and extended cage shape in oriented polymers.
Polymer Science U.S.S.R., 1988
ABSTRACT In practical application, polymeric products are often subjected to mechanical stress. T... more ABSTRACT In practical application, polymeric products are often subjected to mechanical stress. This can be connected both with changes in the rates of chemical reactions in the polymer, and with changes in the diffusion rates of reagents. Previously it has been shown that by drawing of PP [1–3] and PE [3, 4], the accumulation rate of oxygen containing groups formed by polymer interaction with ozone, is enhanced. However, these groups (carbonyls and hydroperoxides) are secondary reaction products of radicals generated in the polymer by the action of ozone. The aim of this work was a study of the effect of drawing stress α on the rate constant of ozone absorption sko3 (s is the coefficient of ozone sorption by PP), on the rate constant of radical formation by this reaction ski, and also on the ozone permeability of PP, sD (D is the diffusion coefficient of O3).
Polymer Science U.S.S.R., 1986
ABSTRACT The authors examine and systematize the experimental data on the dynamics of movements o... more ABSTRACT The authors examine and systematize the experimental data on the dynamics of movements of spin probes in polymers exposed to uniaxial stretching or all-sided compression. It is shown that these results may be explained both in terms of the thermodynamic approach to diffusion and within the framework of the model of the static (rigid) cell of the polymer matrix. The data on the influence of the molecular mobility in polymers on the kinetics of radical reactions are analysed.
Polymer Science U.S.S.R., 1980
ABSTRACT The effect of tension on the oxidation rate of isotactic polypropylene (PP) by ozone has... more ABSTRACT The effect of tension on the oxidation rate of isotactic polypropylene (PP) by ozone has been investigated. The tested films had over-stressed bonds present at the surface. The H atom dissociation was determined from decrease of the long wave wing of the 972 cm−1 IR spectral line recorded by partial internal reflexion. The reaction efficiency was established from the carbonyl groups absorption in the 1700 cm−1 range. The rate of the H atoms dissociation was found to be largest in the overstressed chains. The proportion of deformed bonds dropped during reaction and approached the value typical for a tempered sample. There was no further change in the shape of the absorption line as a result of further oxidation. The supermolecular structure strongly affected the oxidation rate. A % crystallinity and spherule size increase greatly increased the PP stability and ozone resistence, as does thermal-oxidative degradation.
Polymer Science U.S.S.R., 1983
... at least for model compounds, that the ratios kn/ke coincide for seconderT and tel~iary carbo... more ... at least for model compounds, that the ratios kn/ke coincide for seconderT and tel~iary carbon atoms [8]. Figure 2 gives results obtaLaed for the oxidation of IPP films, loaded at ... F. KHUDOSHEV, NI POPIK, MV S~A~LIOr~ and GI KUDRYAVTSEV "Khimvolokno" Production Dept. ...
Polymer Science U.S.S.R., 1983
ABSTRACT The ESR method used to measure the consumption of the stable nitroxyl radical has been e... more ABSTRACT The ESR method used to measure the consumption of the stable nitroxyl radical has been employed to study the kinetics of rupture of the C-C bonds in preoriented isotactic polypropylene under a constant stress σ in isothermal conditions. The kinetics of the consumption of is described by the empirical formula
Polymer Science U.S.S.R., 1986
ABSTRACT The temperature dependence of the static elastic modulus and correlation time of rotatio... more ABSTRACT The temperature dependence of the static elastic modulus and correlation time of rotation of 2, 2, 6, 6-tetramethylpiperidine-1—oxyl has been studied at 210<T<370 K for oriented films of isotactic polypropylene and low- and high-density polyethylene. A parallel trend has been demonstrated in the changes in elastic modulus and correlation time of rotation during the heating and orientation of the polymer, which is evidence that the most defective part of the amorphous phase where the probes are located plays an important part. The proportion of tie chains has been assessed and does not exceed 7%.
Russian Journal of Physical Chemistry B, 2008
The initial stage of the reaction between ozone and hexafluoropropylene (HFP) was studied by the ... more The initial stage of the reaction between ozone and hexafluoropropylene (HFP) was studied by the DFT/B3LYP quantum-chemical method using the family of 6-31G basis sets and the cc-pVDZ+ basis set. Two reaction paths were compared, concerted (the Criegee mechanism) and nonconcerted (the DeMore mechanism) addition. For both reaction paths, the geometry and transition state energies, entropy, and thermodynamic and electronic enthalpy were calculated and the rate constants of the reaction were estimated. It was shown that the DeMore mechanism should be given preference for the reaction of HFP with ozone. UB3LYP calculations for the DeMore mechanism give reaction rate constants close to the experimental values.
Polymer Science U.S.S.R., 1989
ABSTRACT
Polymer Degradation and Stability, 1984
ABSTRACT The effect of stresses on the reactivity of macromolecules in chemical reactions has bee... more ABSTRACT The effect of stresses on the reactivity of macromolecules in chemical reactions has been studied. This effect may be a promoting, inhibiting or neutral effect. Experimental results are satisfactorily explained in terms of a transition complex approach and conformation analysis, by comparison of the energy changes in the initial and transition states under structural strain in a reacting fragment. Our concept, based on the reactivity change, has shed new light on the well-known ‘critical’ strain phenomenon in the ozone corrosion of rubbers. In the case of saturated polyolefins (polyethylene and polypropylene) it was found that the oxidation rate is proportional to exp σ, where σ is the stress, applied to uniaxially oriented films.
Polymer, 1986
ABSTRACT The drawing of semicrystalline polymers induces a wide structural rearrangement that aff... more ABSTRACT The drawing of semicrystalline polymers induces a wide structural rearrangement that affects the organization of the crystalline component and the properties of the amorphous phase. In particular, drawing strongly reduces mobility in the amorphous phase, and this is expected to play a role in the glass transition that is directly connected with mobility in the amorphous component. In agreement with this picture, the elastic modulus data and the electron paramagnetic resonance spectra indicate indirectly that Tg increases on increasing the degree of drawing. This effect depends quantitatively on differences in the degree of drawability of the various samples.
European Polymer Journal
A promoting effect of tensile stress has been revealed for the rate of oxidation of high- and low... more A promoting effect of tensile stress has been revealed for the rate of oxidation of high- and low-density polyethylene and isotactic polypropylene films with ozone. The degree of oxidation and the presence of overstressed bonds on the sample surface were detected by infrared spectroscopy in transmitted and reflected light. Overstressed bonds on the surface were set up by using various quenching regimes and in the bulk by applying a load. The stress-induced changes in segmental mobility of macromolecules were studied by ESR spectroscopy using a stable nitroxyl radical-probe. Supramolecular structure of the samples was investigated by using birefringence, polarized infrared spectroscopy and X-ray diffraction methods. A substantial difference has been found between the stress and the strain dependences of the rate of oxidation of the polymer films with ozone.
It is known that the action of ozone on polymers results in the formation of free radicals. This ... more It is known that the action of ozone on polymers results in the formation of free radicals. This study involves the initiating capability of ozone in reaction with powdered isotactic polypropylene (PP). The chemical reactions are presented on graphs.
Journal of Molecular Structure: THEOCHEM, 2005
Journal of Polymer Science: Polymer Physics Edition, 1983
ABSTRACT Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high... more ABSTRACT Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high-density and low-density polyethylene, and isotactic polypropylene. Experiments have been performed on thin (up to 20 μm) uniaxially oriented films under constant stress σ, under conditions where the chemical kinetics rather than diffusion dominates. It is found that the oxidation rate is proportional to exp(′σ/RT) where ′ is an empirical constant. The effects of unimolecular chain scission and the change of molecular polymer parameters under stress on this dependence are negligible. An analogy with the kinetics of oxidation of stressed cycloparaffins by ozone is noted. A mechanism is suggested to explain the accelerating effect of tensile deformations on chemical processes involving rehybridization of carbon atoms in the main chain from the sp3 to the sp2 state. An ESR study with a stable nitroxyl radical probe revealed a change in the segmental mobility of polymer chains in the course of loading.
Russian Journal of Physical Chemistry B, 2010
The influence of strain in the reaction center containing a double bond on double bond reactivity... more The influence of strain in the reaction center containing a double bond on double bond reactivity at the first stage of the reaction with ozone was studied by the B3LYP density functional theory method and ab initio MP2, CCSD, QCISD, and MRMP2 multireference methods. The 6 31+G** and 6 311+G** basis sets were used. The reactions of ozone with ethylene and butylene were studied. Deformation (ε) was intro duced by using the C=C bond length or the distance between extreme carbon atoms as a coordinate not sub jected to optimization. Stretching of the double bond was found to activate the reaction by the mechanisms of symmetrical and nonsymmetrical addition. The sensitivities to deformation were similar in the two chan nels. When the butene fragment as a whole was stretched, a different picture was observed, and the reaction with ozone was decelerated. In both cases, the logarithms of rate constants linearly depended on ε. The cal culation results were analyzed using the approach developed earlier, which allowed the calculation results to be used to obtain an analytic form of the dependence of activation energy E a on the strength of bonds and to relate deformation induced changes in E a to the length and rigidity of the initial and transition states.
Russian Journal of Physical Chemistry B, 2010
The UQCISD, UB3LYP, UMP2, and MRMP2 methods in conjunction with the 6 31+G**/6 311+G** and aug cc... more The UQCISD, UB3LYP, UMP2, and MRMP2 methods in conjunction with the 6 31+G**/6 311+G** and aug cc PVDZ basis sets are used to study the primary reaction of ozone with chlorinated eth ylene derivatives: tetrachloroethylene, trichloroethylene, 1,2 trans dichloroethylene, 1,2 cis dichloroethyl ene, 1,1 dichloroethylene, and chloroethylene. The reaction is studied for both concerted and nonconcerted ozone addition. The UB3LYP DFT method in conjunction with the 6 31+G** basis set is used to examine various modes of addition of ozone to these chlorinated ethylenes by the Criegee and DeMore mechanisms. The geometry and energy of the transition states, the enthalpy and entropy, and the rate constants and ratios thereof for all the reactions are calculated. The UB3LYP method generally satisfactorily describes the two reaction pathways and, largely correctly predicts the rate constants, in agreement with the available experi mental data. At the same time, this method appears to be inapplicable to modeling the interaction of ozone with 1,1 dichloroethylene. In this case, the single determinant approximation turns out to be unsuitable, and, therefore, MCSCF methods should be used. The MRMP2 method yields reasonable values of the rate constants for the DeMore mechanism, whereas in the case of the Criegee mechanism, the MP2 method does well. The UB3LYP/6 31+G** and UQCISD/aug cc PVDZ methods give similar values of the ratio between the rate constants for the two pathways, a result that demonstrates the versatility of the first one.
Kinetics and Catalysis, 2015
ABSTRACT Quantum chemical calculations have been carried out for the ozonolysis of monofluoro-, m... more ABSTRACT Quantum chemical calculations have been carried out for the ozonolysis of monofluoro-, monochloro-, 1,1-difluoro-, and 1,1-dichloroethylene using the aug-cc-pVDZ basis set by the B2PLYP (B2LYP-D) double-hybrid method involving the Møller-Plesset perturbation theory, the CASSCF multiconfigurational ab initio method with MRMP2 corrections, and the CCSD coupled cluster method. The mechanisms of concerted (Criegee) and nonconcerted (DeMore) additions have been investigated. The CCSD method more precisely simulates these reactions. With the MRMP2 method, the overall reaction rate constant is underestimated because of incomplete geometry optimization, but on the whole the dependence of the rate constant on the nature and number of substituents is practically identical to the dependence predicted by the two other methods. Polar substituents in the molecule increase the contribution from the nonconcerted addition mechanism, which reaches 50% for 1,1-difluoroethylene and 98% for 1,1-dischloroethylene.
Russian Chemical Bulletin, 2004
The N—H bond dissociation energy (DNH) in the 4-anilinodiphenylaminyl radical formed from N,N&... more The N—H bond dissociation energy (DNH) in the 4-anilinodiphenylaminyl radical formed from N,N'-diphenyl-1,4-phenylenediamine was experimentally determined and calculated by the quantum-chemical method. The experimental DNH value was found from the enthalpy of the reaction of N,N'-diphenyl-1,4-benzoquinonediimine with 4-hydroxydiphenylamine taking into account the bond dissociation energies in 4-hydroxydiphenylamine and its aminyl and phenoxyl radicals, which were determined by the intersecting parabolas
Polymer Science U.S.S.R., 1987
ABSTRACT Rate constants of the spin exchange between nitroxide radicals and oxygen in oriented an... more ABSTRACT Rate constants of the spin exchange between nitroxide radicals and oxygen in oriented and isotropic samples of polypropylene, high density and low-density polyethylene were measured over the temperature range of 290–373 K by the method of continuous saturation of the EPR spectrum of the spin probe, and used to calculate oxygen permeability. The results agree with literature data for isotropic samples, but are smaller by 1·5 to 2·5 times upon orientation.
Polymer Science U.S.S.R., 1988
ABSTRACT The rate constant of the reaction of ozone with powdered polypropylene and with isotropi... more ABSTRACT The rate constant of the reaction of ozone with powdered polypropylene and with isotropic or oriented polypropylene films was determined over the temperature interval 300 to 370 K by measuring absorption of ozone. An acceptor of free radicals, (4,4′-dimethoxyphenyl nitroxide), was used to measure the rate of radical formation in polymer samples. The probability that the radical leaves the cage is 2·5-3% in isotropic and 4·5% in oriented polypropylene at 333 K. The results are discussed in terms of anisotropic microdiffusion and extended cage shape in oriented polymers.
Polymer Science U.S.S.R., 1988
ABSTRACT In practical application, polymeric products are often subjected to mechanical stress. T... more ABSTRACT In practical application, polymeric products are often subjected to mechanical stress. This can be connected both with changes in the rates of chemical reactions in the polymer, and with changes in the diffusion rates of reagents. Previously it has been shown that by drawing of PP [1–3] and PE [3, 4], the accumulation rate of oxygen containing groups formed by polymer interaction with ozone, is enhanced. However, these groups (carbonyls and hydroperoxides) are secondary reaction products of radicals generated in the polymer by the action of ozone. The aim of this work was a study of the effect of drawing stress α on the rate constant of ozone absorption sko3 (s is the coefficient of ozone sorption by PP), on the rate constant of radical formation by this reaction ski, and also on the ozone permeability of PP, sD (D is the diffusion coefficient of O3).
Polymer Science U.S.S.R., 1986
ABSTRACT The authors examine and systematize the experimental data on the dynamics of movements o... more ABSTRACT The authors examine and systematize the experimental data on the dynamics of movements of spin probes in polymers exposed to uniaxial stretching or all-sided compression. It is shown that these results may be explained both in terms of the thermodynamic approach to diffusion and within the framework of the model of the static (rigid) cell of the polymer matrix. The data on the influence of the molecular mobility in polymers on the kinetics of radical reactions are analysed.
Polymer Science U.S.S.R., 1980
ABSTRACT The effect of tension on the oxidation rate of isotactic polypropylene (PP) by ozone has... more ABSTRACT The effect of tension on the oxidation rate of isotactic polypropylene (PP) by ozone has been investigated. The tested films had over-stressed bonds present at the surface. The H atom dissociation was determined from decrease of the long wave wing of the 972 cm−1 IR spectral line recorded by partial internal reflexion. The reaction efficiency was established from the carbonyl groups absorption in the 1700 cm−1 range. The rate of the H atoms dissociation was found to be largest in the overstressed chains. The proportion of deformed bonds dropped during reaction and approached the value typical for a tempered sample. There was no further change in the shape of the absorption line as a result of further oxidation. The supermolecular structure strongly affected the oxidation rate. A % crystallinity and spherule size increase greatly increased the PP stability and ozone resistence, as does thermal-oxidative degradation.
Polymer Science U.S.S.R., 1983
... at least for model compounds, that the ratios kn/ke coincide for seconderT and tel~iary carbo... more ... at least for model compounds, that the ratios kn/ke coincide for seconderT and tel~iary carbon atoms [8]. Figure 2 gives results obtaLaed for the oxidation of IPP films, loaded at ... F. KHUDOSHEV, NI POPIK, MV S~A~LIOr~ and GI KUDRYAVTSEV "Khimvolokno" Production Dept. ...
Polymer Science U.S.S.R., 1983
ABSTRACT The ESR method used to measure the consumption of the stable nitroxyl radical has been e... more ABSTRACT The ESR method used to measure the consumption of the stable nitroxyl radical has been employed to study the kinetics of rupture of the C-C bonds in preoriented isotactic polypropylene under a constant stress σ in isothermal conditions. The kinetics of the consumption of is described by the empirical formula
Polymer Science U.S.S.R., 1986
ABSTRACT The temperature dependence of the static elastic modulus and correlation time of rotatio... more ABSTRACT The temperature dependence of the static elastic modulus and correlation time of rotation of 2, 2, 6, 6-tetramethylpiperidine-1—oxyl has been studied at 210<T<370 K for oriented films of isotactic polypropylene and low- and high-density polyethylene. A parallel trend has been demonstrated in the changes in elastic modulus and correlation time of rotation during the heating and orientation of the polymer, which is evidence that the most defective part of the amorphous phase where the probes are located plays an important part. The proportion of tie chains has been assessed and does not exceed 7%.
Russian Journal of Physical Chemistry B, 2008
The initial stage of the reaction between ozone and hexafluoropropylene (HFP) was studied by the ... more The initial stage of the reaction between ozone and hexafluoropropylene (HFP) was studied by the DFT/B3LYP quantum-chemical method using the family of 6-31G basis sets and the cc-pVDZ+ basis set. Two reaction paths were compared, concerted (the Criegee mechanism) and nonconcerted (the DeMore mechanism) addition. For both reaction paths, the geometry and transition state energies, entropy, and thermodynamic and electronic enthalpy were calculated and the rate constants of the reaction were estimated. It was shown that the DeMore mechanism should be given preference for the reaction of HFP with ozone. UB3LYP calculations for the DeMore mechanism give reaction rate constants close to the experimental values.
Polymer Science U.S.S.R., 1989
ABSTRACT
Polymer Degradation and Stability, 1984
ABSTRACT The effect of stresses on the reactivity of macromolecules in chemical reactions has bee... more ABSTRACT The effect of stresses on the reactivity of macromolecules in chemical reactions has been studied. This effect may be a promoting, inhibiting or neutral effect. Experimental results are satisfactorily explained in terms of a transition complex approach and conformation analysis, by comparison of the energy changes in the initial and transition states under structural strain in a reacting fragment. Our concept, based on the reactivity change, has shed new light on the well-known ‘critical’ strain phenomenon in the ozone corrosion of rubbers. In the case of saturated polyolefins (polyethylene and polypropylene) it was found that the oxidation rate is proportional to exp σ, where σ is the stress, applied to uniaxially oriented films.
Polymer, 1986
ABSTRACT The drawing of semicrystalline polymers induces a wide structural rearrangement that aff... more ABSTRACT The drawing of semicrystalline polymers induces a wide structural rearrangement that affects the organization of the crystalline component and the properties of the amorphous phase. In particular, drawing strongly reduces mobility in the amorphous phase, and this is expected to play a role in the glass transition that is directly connected with mobility in the amorphous component. In agreement with this picture, the elastic modulus data and the electron paramagnetic resonance spectra indicate indirectly that Tg increases on increasing the degree of drawing. This effect depends quantitatively on differences in the degree of drawability of the various samples.