D. A. Gordon

Methyl acrylate and methyl methacrylate oligomerization initiated by radicals generated via low-temperature treatment with molecular chlorine

By means of liquid chromatography, UV spectroscopy, calorimetry, and elemental analysis, it has been shown that the radicals generated spontaneously during low-temperature (77 K) mixing of the methyl acrylate (MA) and methyl methacrylate (MMA) monomers with molecular chlorine initiate the MA and/or MMA oligomerization reaction. The oligomerization and chlorination reactions occur as the mixtures prepared at 77 K are heated, having the reaction onset temperature below the chlorine melting point (170 K) and a maximal rate in the MA premelting region (180–190 K) for the MA-Cl2 mixture or the MMA melting range (220–230 K) for the MMA-Cl2 mixture.

Low temperature radiolysis of fullerene C60 and its solutions in isopropylbenzene and N-vinylpyrrolidone

Low-temperature (77 K) radiolysis of solid fullerene C60 and its glassy solutions in isopropylbenzene (IPB) and N-vinylpyrrolidone (N-VP) has been investigated with the use of ESR spectroscopy. Radiationchemical yields for the formation of paramagnetic centers (GPMC, 1/100 eV) have been determined to be ∼0.001 for pure fullerene and 0.3 and 0.7 for its solutions in IPB and N-VP, respectively. The low value of GPMC for fullerene indicates a high stability of this form of carbon. The increase in GPMC in solutions as compared to the pure solvents (0.15 for IPB and 0.3 for N-VP) indicates the sensitizing effect of C60.

Processes occurring during the interaction of molecular bromine with acrylamide at low temperatures and upon heating the mixture

It has been shown that the addition of molecular bromine to the monomer acrylamide (AA) results in the spontaneous formation of radicals. During heating the AA + Br2 mixture, the radicals initiate polymerization and bromination reactions. Beginning well below the melting point of bromine, both the reactions proceed at a noticeable rate at its melting temperature.

Spontaneous formation of free radicals in cryochemical reactions of halogenation of hydrocarbons and nanomaterials

A range of issues related to free-radical processes in polymer-monomer systems is considered. Spectral (EPR, IRS) and other physicochemical methods (calorimetry, chromatography, viscometry) are used to demonstrate that the low-temperature treatment of polymers and monomers with halogens (fluorine, chlorine) is accompanied by the spontaneous formation of free radicals. At F2 and Cl2 pressures below 100 Torr, the concentration of radicals reaches 1017–1019 spin/g, which can be reproduced in the case of radiolysis only by using doses of several hundred (or thousand) kGy. The formation of radicals through the cleavage of chemical bonds (without external energy impact on the system) is discussed in the framework of the model of low-temperature reactions in polymolecular complexes, involving the simultaneous occurrence of endothermic and exothermic steps in one elementary event with an overall exothermic effect. It is shown that the radicals formed can be used to initiate the polymerization of vinyl and acetylene monomers.

Characteristics of the radical polymerization of acetylene monomers

The radical polymerization of acetylene monomers is studied via electron spin resonance (ESR) spectroscopy, calorimetry, chromatography, and gravimetry within a wide range of temperatures (77–340 K). A growing macroradical with an unpaired electron localized on the terminal moiety of a macromolecule is shown to lose its activity, due to the delocalization of electron over the conjugated system of double bonds after attaining the very short length of 5–10 monomer units. This explains the low conversion and molecular masses of the synthesized polymers.

Synthesis of water-soluble fullerene-containing vinyl polymers by low-temperature radiation-induced living polymerization

Water-soluble polymers of acrylamide and acrylic acid that contain fullerene (more than 90% C60) have been prepared by the low-temperature radiation-induced living polymerization. In the absorption spectra of these polymers, a monotonically decaying absorption typical of the covalently bound fullerene or its associates is observed in the range 240–700 nm. The radiation initiation of the process allows preparation of high-purity polymers useful for designing medicinal preparations.

Processes occurring under the action of molecular bromine on methyl acrylate at low temperatures and during heating the resulting mixture

With the use of EPR, UV–VIS, and IR spectroscopy, calorimetry, and elemental analysis, it has been found that radicals are spontaneously formed under the action of molecular bromine on the methyl acrylate (MA) monomer at low temperatures; upon heating the system (225 K), these radicals initiate a polymerization reaction. This process is not efficient. The addition of bromine at the double bond of MA is the main reaction that occurs during the heating of the system (225 K).

Water-soluble fullerene С 60 derivative obtained by radiation polymerization of N -vinylpyrrolidone in the presence of С 60

Method of radiation polymerization of N-vinylpirrolidone (NVP) in the presence of fullerene C60 has been used to obtain water soluble compound containing fullerene C60. The yield of resulted product was ~10% in the case of low-temperature radiation polymerization of NVP—C60 mixture in ethanol and ~40% at 300 K. The content of C60 in obtained product was ~0.5 wt.%.

Features of the processes occurring during low-temperature reactions between molecular chlorine and monomers and during the heating of mixtures

Using EPR, UV, VIS, and IR spectroscopy; chromatography; calorimetry; elemental analysis; and gravity, it has been shown that low-temperature reactions between molecular chlorine and some acetylenic and/or vinyl monomers lead to the spontaneous formation of radicals without involving any external energy impact. The resulting radicals initiate polymerization and chlorination reactions that occur during the heating of mixtures prepared at 77 K. In mixtures where the monomers are solids under normal conditions, the polymerization and chlorination reactions occur in the range of the melting point of chlorine. In mixtures where the monomers are liquids, the reactions begin at temperatures below the melting point of chlorine (170 K) and occur at a maximum rate in the region of the melting point of the monomer. The main reaction products are oligomers. The last-mentioned fact suggests that the spontaneously formed chloroalkyl radicals more readily react with the monomer molecules than with the caged chlorine radical.

Reactions between Molecular Chlorine and Acrylates over a Wide Range of Temperatures

EPR, UV, VIS spectroscopy, chromatography, calorimetry, elemental analysis, and gravimetry are used to show that radicals formed spontaneously upon low temperature (77 K) interaction between molecular chlorine and methyl acrylate and/or methyl methacrylate initiate reactions of polymerization and chlorination that proceed under heating in a monomer system + Cl2 prepared at 77 K. It is established that beginning at the premelting temperature of chlorine, both reactions mostly proceed at the temperatures of monomer melting, and the main reaction products are oligomers. It is concluded that chloroalkyl radicals formed spontaneously at 77 K react more readily with monomer molecules than do chlorine radicals in a cell.