M. I. Cherkashin

Intermolecular interaction in polyconjugated systems

1. n nThe thermochemical characteristics of a number of low-molecular and polymer compounds with a system of conjugation were investigated. n n n n n2. n nThe energies of stabilization of the systems studied were found, and it was proposed that they are due chiefly to intermolecular interaction.

Direct detection of free radicals by EPR method during the polymerization of compounds of the acetylenic series

When the thermal bulk polymerizat ion of phenylacetylene, diphenylacetylene, p-iodophenylacetylene, phenoxyacetylene and diphenylbutadiyne (DPBD) is ca r r i edou t directly in an EPR spec t romete r at 150 o an intense EPR signal is observed immediately. In all cases , with the exception of DPBD, the EPR signal represen ts a single absorption line with a g factor that is close to the g factor of a free electron. In the polymerizat ion of DPBD the EPR signal has a hyperfine s t ruc ture (HFS) that consists of at least four lines, with a splitting of 35 Oe between the ext reme components. The two middle HFS lines are masked by an intense central signal, which has the same nature as the single absorption line in polyphenylacetylene, polydiphenylbutadiyne, and other polymers containing a conjugation system. Since the EPR signal disappears when the mater ia l is cooled to a t empera ture where the polymerizat ion of the corresponding monomer fails to occur , and the process is inhibited by N,N-diphenylpicrylhydrazyl , it may be assumed that we were the f i rs t to use the EPR method to direct ly detect the free radicals that take part in the polymerizat ion of c o m pounds of the acetylenic se r i es .

Photoelectric properties of a system of polymer with conjugated bonds and electron acceptor compound

1. n nThe presence of a photoeffect in polymers with a system of conjugation was demonstrated in an electrophotographic system, but the value of the photosensitivity is small. n n n n n2. n nThe introduction of low-molecular electron acceptor compounds into polymers with a system of conjugation leads to an appreciable increase in the electrophotographic sensitivity. n n n n n3. n nFor the donor polymer-acceptor polymer system, an increased photosensitivity is observed, with a simultaneous conservation of film-forming properties and thermal stability. n n n n n4. n nThe mechanism of the chemical sensitization of the photoconductivity was studied in a heterophase system of conjugated polymer-electron acceptor compound. In such a system the process consists of sensitization of the organic semiconductor by electron acceptor compounds, adsorbed on its surface with polymer molecules.

Nitration of polyarylvinylenes

1. n nThe nitration of polyarylvinylenes, which proceeds according to the type of electrophilic substitution, leads to the formation of polymer-analog products. n n n n n2. n nThe introduction of a nitro-group into polyphenylacetylene is accompanied by the appearance of a hyperfine structure in their EPR spectra as a result of interaction of the unpaired electrons with the nitrogen nucleus.

Hydrogenation of polyarylvinylenes

1. n nPolyarylvinylenes are distinguished by low activity in hydrogenation reactions, which is due to the presence of a highly developed system of conjugation. n n n n n2. n nThe hydrogenation of catalytic and thermal polyphenylacetylenes is accompanied by a decrease in the concentration of paramagnetic centers, permitting the conclusion that they belong to polyconjugated macromolecules, and not to impurities. n n n n n3. n nFrom the nature of the NMR spectra of the hydrogenation products it can be concluded that hydrogenated polyphenylacetylene has an atactic structure. n n n n n4. n nIt is believed that the hydrogenated polymers are a difficult-to-separate mixture of entirely hydrogenated and unhydrogenated macromolecules.

Some principles of the thermal polymerization of phenylacetylene and 2-methyl-5-ethynylpyridine

1. n nThe kinetics of the polymerization of phenylacetylene and 2-methyl-5-ethynylpyridine was studied, and the rate constants of the thermal polymerization and observed activation energies were determined. n n n n n2. n nOn the basis of an analysis of the products of thermolysis and ozonization of polyphenylacetylene it was shown that the chain of polymer is constructed chiefly according to the “head-to-tail” principle. n n n n n3. n nA biradical mechanism of the initiation of the thermal polymerization of phenylacetylene was proposed.

The structure of the chain of polyphenylacetylene

To elucidate the structure of the polymeric chain of polyphenylaeetylenes obtained b~polymerization in the catalytic system TiC1 + AI(C2Hs) 3 (Mn = 5100, 2600) and by thermal polymerization (M n = 1100), we carried out the ozonolysis of the polyphenylaeetylenes in CC14 solution at --30~ The ozonization products were oxidized to acids and these were converted into esters by methylation with diazomethane. A chromatographic analysis showed that the yield of diketone (CGttsCOCOC6IIs) , corresponding to head to head addition, did not exceed 5-7%, while the total yield of methyl esters of phenylglyoxalie and benzoic ackts amounted to ~75%. Consequently, the polyphenylaeetylene chain is consh~cted mainly in the ,,head to taW manner.

Structure of polymers of dimethylbutadiyne

1. n nThe thermal and catalytic polymerization of dimethylbutadiyne leads to polymers that are readily oxidized by atmospheric oxygen. n n n n n2. n nAs a result of polymerization, a block copolymer is formed, containing fragments of a substituted polyene and polyacene, together with a small amount of double bonds of the basic chain, isomerized into the side chain. n n n n n3. n nThe insolubility of the thermal polymer is apparently due to the formation of a three-dimensional structure during synthesis, while for the catalytic polymer this apparently occurs at the stage of its treatment.

Thermochemical investigations of copolymers and block copolymers containing polyvinylene blocks in their structure

1. n nA thermochemical method was used to analyze the composition and structure of copolymers and block copolymers containing polyvinylene blocks in a macrochain. n n n n n2. n nIn the copolymerization of phenylacetylene with maleic anhydride, products with a structure containing blocks of conjugation are formed. n n n n n3. n nThe values of the molecular weights of the block copolymers of polyphenylacetylenes with maleic anhydride and furmarodinitrile were estimated on the basis of a determination of the heats of combustion.

Possibility of determining the composition and structure of cyclic products formed in the polymerization of phenylacetylene by the NMR method

1. n nA simple method was proposed for determining the content and composition of cyclic trimers in the polymer according to the NMR spectra. n n n n n2. n nThe possibility of using data on cyclic trimers to solve the problem of the mechanism of the polymerization process and the structure of the polymer chain was demonstrated.