Volume Effect Of Activation Research Articles

Uniaxial stretching induced pore nucleation and growth in row-nucleated crystalline hard-elastic polypropylene film: The effect of activation volume and stretching work

In this paper, the pore nucleation and growth during uniaxial stretching of polypropylene hard-elastic film at different temperatures were followed. The stretching-induced microstructure including lamellar clusters, fibrillar crystals and pores were tracked by in-situ x-ray scattering. The correlation between activation volume and lamellar clusters thickness and the relationship between stretching work and the new formed fibrillar crystals/pore surface area were built. It was found that compared with that obtained at 105 °C, the hard-elastic film stretched at 145 °C induced larger lamellar cluster thickness, longer fibrillar crystals and fewer pores with larger size. With the stretching temperature increasing, the chain segment activation volume increases, whereas the activation energy and stretching work decreases. During uniaxial stretching, the stretching work was mainly dissipated by forming new surfaces. Higher activation volume lead to larger lamellar cluster thickness and less pore number in unit area, whereas lower activation energy induced longer fibrillar crystals and lower stretching work resulted in less new surface. This paper clarifies how the stretching temperature affect pore formation and growth during the uniaxial tensile deformation of hard elastic film and the obtained results are beneficial for the pore control during the industrial fabrication of polypropylene microporous membrane.

Effect of activation volume on the induced superconductivity in tenary system[formula omitted

Using the theory of absolute reaction or transition state theory to calculate the temperature-dependent resistance tuned by the activation energy as well as the activation volume considering the presumed wavy-roughness along the sub-nano domains we can identify critical dynamical transitional phases of electronic liquids in a tenary system: (AusAg1−s)yYb1−y (0 ≤ s ≤ 1.0 and 0 ≤ y ≤ 1.0). After calibation or validation of our approach with previous measurements we for the first time found the critical temperature relevant to the sudden jump to almost-zero normalized resistance states or nearly frictionless transport of many condensed electrons in above mentioned tenary system being around 12 K.

Effect of activation volume on the defect-induced anomalous electronic transport in Rb $$_{0.8}$$ 0.8 Fe $$_2$$ 2 Se $$_2$$ 2

We adopted an absolute-reaction model which is considering the hole(defect)-induced charged frictionless transport to explain the unusual experiment: Two single crystalline samples of the same nominal composition Rb $$_{0.8}$$ Fe $$_2$$ Se $$_2$$ were prepared using the self-flux technique via two different precursor routes. Although the difference in the final chemical composition falls within a narrow range, one was superconducting with a $$T_c \sim 31$$ K, while the other behaves like a narrow gap semiconductor.

Influence of water fugacity and activation volume on the flow properties of fine‐grained anorthite aggregates

To specify quantitatively the effect of pressure and water weakening on the flow strength of feldspar we performed triaxial creep experiments in a gas deformation apparatus at temperatures of 1000–1150°C, confining pressures of 100–450 MPa, and axial stresses of 10–400 MPa, resulting in strain rates of ∼6 × 10−7 to 3 × 10−3 s−1. Dense samples with a grain size of ∼3 μm were prepared by hot‐isostatic pressing of anorthite glass powder. Hydrous samples contain about 0.33 ± 0.14 wt % H2O and dry specimens 0.0005–0.02 wt % H2O. The estimated residual glass content of wet samples is <2 vol %. Samples deformed by grain boundary diffusion‐controlled creep at low stresses and dislocation creep at stresses ≳150 MPa. We estimate an activation volume of V ≈ 24 cm3mol−1 for anhydrous samples deforming in diffusion creep. For wet samples, deformed in hydrous conditions with varying buffers fixing oxygen fugacity, the activation volume is about 38 cm3 mol−1. Creep rate of hydrous anorthite aggregates depends on water fugacity raised to a power of r = 1.0 ± 0.3, suggesting hydrolysis of oxygen bonds. Considering the effect of activation volume and water fugacity on extrapolation of constitutive laws to conditions prevailing in the continental lower crust, viscosities of hydrous feldspar aggregates increase by a factor of <3.

Effect of High Pressure on the Kinetics and Mechanism of Thermolysis of Organic Peroxides in Solution

AbstractFor Abstract see ChemInform Abstract in Full Text.

Effect of High Pressure on the Kinetics and Mechanism of Thermolysis of Organic Peroxides in Solution

This review analyzes published data and experimental results obtained by the authors concerning the effect of high pressure on the chemical kinetics of thermal decomposition of the main types of organic and organosilicon peroxides in solution. The volume effect of activation was found to depend on the mechanism of peroxide decomposition and on the properties of solvents.

Effect of the pressure on the rate of menschutkin reactions and analysis of the volume effects of activation of sterically hindered reactions

1. The equation which describes the effect of the pressure on the rate of nonionic organic reactions is also applicable to Menschutkin reactions, processes with a strongly polar transition state. 2. The explanation of the additional decrease in the volume effect of activation in sterically hindered Menschutkin reactions by movement of the transition state along the reaction coordinate is unsubstantiated. This effect is attributed to the steric interaction of valence-nonbound groups of atoms. 3. Solvation of the strongly polar transition state results in an increase in the isothermal compressibility coefficient ΔV0≠.

Influence of the pressure on the rate constants of the elementary stages of the homolytic decomposition of organic compounds

1. An equation describing the influence of the pressure on the rate constant of liquid-phase homolytic bond-cleavage reactions has been obtained. 2. A difference in the values of (∂ΔV≠/∂p)p=0/ΔV0≠ in addition and homolytic bond cleavage reactions and in diffusional processes has been found which is explained by the different contribution of the free volume to the volume effect of activation (ΔV0≠). In addition reactions and reactions involving the radical detachment of a hydrogen atom the values of (∂ΔV≠/∂p)p=0/ΔV0≠ are close to one another, and the contributions of the free volume to ΔV0≠ are approximately the same. 3. An equation has been proposed for describing the influence of the pressure on the viscosity of liquids. It has been shown that a linear relationship of free energies with a change in the pressure is inapplicable for this process.

Linear correlation between constants of substituents and volume effects of activation

Linear correlation between constants of substituents and volume effects of activation

Influence of high pressure on the reaction of radical substitution

1. The volume effect of activation in radical reactions of chain transfer through CCl4 depends little on. the structure of the radical and is close to the corresponding effect in the reaction of chain propagation. 2. Substantial changes in the volume effect of activation of the reaction of stripping of a hydrogen atom by a free radical are associated chiefly with the difference in the lengthening of the C-H bond in the formation of the transition state. Calculation showed that the stretching of the C-H bonds may reach a value of the order of 80% of its normal length.

Effect of high pressure on the radical polymerization of methyl methacrylate, inhibited by p-benzoquinone

The inhibition by p-benzoquinone (BQ) of polymerization of methyl methacrylate in the presence of 2·08 × 10 −2mole/1. of azobisisobutyronitrile has been studied at 50° (2·08 × 10 −3mole/1 of BQ) and at 70° (2·08 × 10 −2 mole/1. of BQ) at pressures from 1 to 8000 kg/cm 2. Pressure has practically no accelerating effect under these conditions and this is explained by a low probability of chain regeneration (⪡1) at all pressures. The volume effect of activation in the reaction of addition of a polymeric radical to monomer (chain propagation) is 2·9−7·4 cm 3/mole greater in absolute value than in addition of the same radical to BQ.

Influence of pressure on asymmetric synthesis

1. The influence of pressure on asymmetric diene condensation of butadiene with di-(−)-menthyl fumarate was investigated. At atmospheric pressure (70°), the optical yield is equal to 0; at 5000 kg/cm2, an excess of the di-(−)-menthyl ester of (+)-Δ4-trans-cyclohexene-1,2-dicarboxylic acid is formed with an optical yield of 4.7%. 2. In the reaction studied, the transition state in the formation of the dimenthyl ester of the (+)-acid is characterized by lower values of the energy, entropy, and volume than in the case of the (−)-acid. 3. The role of the change in the free volume as a component of the volume effect of activation was discussed. It was concluded that there is a relationship between the steric hindrance of the reaction and the change in the free volume in the formation of the transition state. 4. Hypotheses are expressed on the principles of the influence of pressure on asymmetric synthesis.

Influence of pressure on the particular transfer constants and stereodirectedness of radical telomerization of ethylene and propylene with carbon tetrachloride and chloroform

1. The particular constants of chain transfer in the telomerization of ethylene with CCl4 and CHCl3 and propylene with CCl4 at 95° and a pressure of 150–180 or 2400 kg/cm2 were determined. The change in the rate of reactions of substitution with cleavage of a C-H bond with increasing pressure (and the volume effects of activation) is substantially lower than for substitution of the C-Cl bond with the participation of the same trichloroalkyl radicals. 2. Increasing the pressure increases the probability of the formation of the racemic iso-modification of 1,1,1,1-tetrachloro-3,5-dimethyloctane in the radical telomerization of propylene with CCl4. The reaction of addition or substitution of CCl3[CH2CH(CH3)]n radicals with conservation of the configuration of the preceding unit proceeds through transition states with a somewhat smaller volume than for processes with syndiotactic chain propagation.

Volume effects of activation in certain reactions of aromatic substitution

1. A calculation was made of the “volumes of overlapping” according to the models of the activated complex for the homolytic phenylation of tert-butylbenzene by benzoyl peroxide in the ortho-and parapositions. The results of the calculation are in satisfactory agreement with the difference of the volume effects of activation in the formation of ortho-and para-tert-butyl diphenyls, found according to the data on the influence of pressure upon the structural direction of the indicated reaction. 2. A calculation was made of the “volumes of overlapping” in the formation of unstable intermediate addition products in reactions of nucleophilic aromatic substitution —the interaction of n-butyl-and tertbutylamines with 2,4-dinitrochlorobenzene. The calculation was based upon the presumed structure of the addition product. The results of the calculation proved close to the values of the volume effects of activation found according to data on the influence of pressure upon the rate of these reactions. However, the difference in the calculated volume effects in the case of tert-butyl-and n-butylamines was appreciably greater than that found experimentally, which is evidently due to steric hindrance of the solvation of the intermediate addition product in the reaction with tert-butylamine. 3. The results of the work confirm the possibility of using models of the activated complex for a priori comparison of the steric hindrance and the accelerating effect of pressure in a series of monotypic chemical reactions.

Influence of pressure on the radical polymerization of styrene in solution Communication 2. Polymerization in para-butyraldehyde, butyraldehyde, and their mixtures

1. The radical polymerization of styrene in para-butyraldehyde, included by azoisobutyrodinitrile, was investigated at 50°. The rate and average degree of polymerization increase substantially when the pressure is raised to 4000 kg/cm2. On the basis of the data on the influence of pressure on the rate and average degree of polymerization, it was concluded that the rate constants of initiation and chain termination decrease with increasing pressure. The values of the volume effects of activation in initiation and chain termination were estimated. 2. The dependence of the change in the average degree of polymerization on the molar ratio butyraldehyde: styrene was investigated at pressures up to 4000 kg/cm2. The data obtained confirm our earlier conclusion of a substantial decrease in the ratio of the rate constants of chain transfer through butyraldehyde and chain propagation in the polymerization of styrene at increased pressure.

Effect of pressure on structural and steric orientation in diene synthesis Communication 1. Condensation of 1-vinylcyclopentene with methyl acrylate

1. Increase in pressure from atmospheric to 6000 Kg/cm2 leads to a change in structural and steric orientation in the diene condensation of 1-vinylcyclopentene with methyl acrylate which favors the formation of the ortho-cis isomer. The relative amounts of the other three isomers scarcely change when pressure is applied. 2. For the analysis of the volume effects of activation in the system studied a cyclic transition state was assumed with a structure intermediate between that of a model with a parallel arrangement of the planes of the diene and dienophile, on the one hand, and the structure of the adduct, on the other. Such a transition state is in full accord with the experimental data obtained. 3. In the reaction studied the relative amounts of the stereoisomeric ortho adducts are determined mainly by electronic, not steric, effects.