V. P. Volkov

The mechanism of decay of active centres in polymerization of trioxan in solution

As a result of kinetic and spectrophotometric studies of the polymerization of trioxan with B+A− salts as catalysts (where B+ = Ph3C+, CH3CO+ or CH3OCH2+, and A− = SbCl6− or SbF6−) it has been found that termination of the growing chains involves both physical and chemical processes the ratio of the two being dependent on the structure of the active centres and on the conditions of polymerization.

The mechanism of initiation of polymerization of trioxan in the presence of tritylium salts

A study has been made of the mechanism of initiation of the polymerization of trioxan in benzene, catalysed by tritylium salts. Polymerization of trioxan in the presence of Ph3C+SbF6− (in the absence of water) is initiated by abstraction of a hydride ion from the monomer molecule. When Ph3C+SbCl6− is used SbCl5, formed by decomposition of the trytilium salt in solution, plays an important part in initiation. Efficient hydride ion donors (1,3-dioxolane, tetrahydrofuran) and also linear acetals and epoxides, substantially increase the rate of initiation in polymerization of trioxan in the presence of trityl salts. Compounds containing hydroxyl groups (water, alcohols), cycloheptatiene and triethylsilane inhibit the initiation reaction.

Kinetics and mechanism of polymerization of 1,3-dioxolane in various media under the action of methoxymethylhexachlorantimonate☆

The polymerization of 1,3-dioxolane under the action of CH3OCH2SbCl6 and PhCSbF6 has been investigated in various media. The effective constants for the dissociation of active propagating sites with a hexachlorantimonate counter ion, to molecular forms, have been determined and the dependence of these constants on the dielectric permeability of the medium has been discussed. It is shown that the rate constants for chain propagation at the free ion and at an ion pair differ by a factor of 3. It has been establishedthat an increase in the ionic strength of the polymerization solution leads to an increase in the concentration of active site having a hexachlorantimonate counter ion and to a decrease in the polymerization rate constant.

Relation between synthesis processes and structure formation of polyoxymethylene

It was found that the conformation structure of (CH2O)n chains recorded during crystallization of polyoxymethylene in the course of synthesis, depends on conditions of polymerization of trioxane (type of catalyst, presence of chain carriers and comonomer, solvent, temperature) and is determined by the physical condition of active centres of growing macromolecules localized on the surface of crystallites or in solution. The physical condition of active centres determines the relation between polymer structure and its evolution during polymerization and process kinetics.

Effect of functionality of oligophenolic hardener on structural and kinetic features of formation and on properties of epoxy-phenolic cross-linked polymers

Kinetics of the reaction of resorcinol diglycidyl ether with novolac phenol-formaldehyde resins of various functionalities were studied over a wide temperature range by isothermal calorimetry. The effects of the functionality of oligophenols on curing of epoxy-phenolic composites, structure of the resulting polymer at the chemical, topological, and supramolecular levels, its mechanical and relaxation properties, and the mechanism of its fracture were analyzed.

Phenomenological Description of the Mechanisms of Deformation and Degradation of Polypropylene Particles during Mechanochemical Modification in the Solid Phase

This work considers the mechanism of deformation and degradation of polypropylene (PP) particles during solid phase mechanochemical modification in an extruder. Electron microscopy was used to investigate the morphological changes to particles of different dimensions (4 hierarchical levels), their internal structure and surface during increases in the duration and intensity of their exposure to mechanochemical impacts in an extruder. We provided a detailed description of the morphology of the original PP in references (refs.. 1–3). Table 1 contains information on the structure of the particles of the original PP.

Influence of Time and Intensity of Solid Phase Mechanochemical Modification on the Morphology of Polypropylene Particles

An investigation of the dynamics of the change to the granulometric structure of polypropylene (PP) when modified in a solid state of aggregation (ref. 1) identified a correlation between the degree of grafting of a comonomer with the degree of plastic deformation of the polymer particles. The plastic deformation of the material is assessed (ref. 1) from the change in the particle dimensions by means of particle size analysis. The objective of this work was to investigate the influence of the intensity and time of mechanochemical modification of PP in a solid state of aggregation on the morphology of the particles and to compare the results of electron microscopy with the results of particle size analysis. The particles were grouped in four different hierarchical levels differentiated by order of magnitude. The levels were as follows: 1 – (0.1–1.0 μm), 2 – (1.0–10 μm), 3 – (10–100 μm) and 4 – (10000 μm). The fourth structural level of the polymer contained particles from all three finer levels (for more details see [refs. 2–4]). Where plastic deformation and the degradation of the material caused a change to the specific surface of the polymer, we evaluated it for materials produced in different conditions. The results obtained were compared with a number of grafted –COOH groups in different material fractions produced in similar conditions (refs. 1, 5).

Spectrophotometric study of the structure and reactivity of organic salts of hexachloroantimonic acid

Abstract In a study of the electronic spectra of onium and carbonium salts of hexachloroantimonic acid it has been found that the absorption band with λ max = 272 nm is produced by electronic transitions in the free SbCl 6 − anion and in the ion pair R + SbCl 6 − , and is independent of the nature of the cation. The cation strongly affects the stability of the SbCl 6 − anion. It is shown that carboxonium salts, which are active centres for polymerization of cyclic acetals or are formed in initiation of polymerization of tetrahydrofuran by trityl hexachloroantimonate, are unstable and decompose reversibly to the molecular forms.