Radiation synthesis of telomers at a constant tetrafluoroethylene concentration in acetone

Radiation-initiated polymerization of tetrafluoroethylene (TFE) in acetone has been carried out in a specially designed reactor, which makes it possible to maintain a constant concentration of the monomer in a solution during synthesis. The features of the telomerization process at different initial concentrations (pressures) of TFE have been studied. Concentrated solutions of telomers have been obtained. The carrying out of the process at different pressures in the reactor makes it possible to obtain telomers differing in molecular mass and thermal resistance.     

Radiation-chemical synthesis of tetrafluoroethylene telomers in chloropentafluorobenzene and perfluoroxylene

The kinetics of radiation-induced telomerization of tetrafluoroethylene in chloropentafluorobenzene and perfluoroxylene have been studied. Colloidal solutions of thermally stable tetrafluoroethylene telomers with a chain length of 50–160 units have been obtained. A comparative analysis of the reactivity of some monohalogenated benzene derivatives used as telogens has been performed.     

Radiation synthesis of tetrafluoroethylene telomers in chlorosilanes and their use for modification of aluminoborosilicate glass fabric

The kinetics of radiation-initiated telomerization of tetrafluoroethylene in dichlorodimethylsilane and chlorotrimethylsilane have been studied, and the molecular structure and properties of the telomers have been revealed. It has been shown that the introduction of ~3.5 wt % product telomer into aluminoborosilicate glass fabric gives a fluorinated glass-reinforced polymer material with good hydrophobicity.     

NMR identification of the terminal groups of the telomers of tetrafluoroethylene with tetrahydrofuran

¹H, ¹³C, and ¹⁹F high-resolution NMR spectra with heteronuclear spin-spin decoupling and without it were recorded for identification of the terminal groups of oligomers obtained by radical polymerization of tetrafluroethylene (TFE) in tetrahydrofuran (THF) solutions. The analysis of the spectra and their comparison with the quantum-chemically calculated spectra of possible polymerization products led to the conclusion that the terminal groups of oligomers are the α radical of THF and the hydrogen atom. The structure of oligomers found in this study opens up an opportunity of synthesizing from them polymers consisting of a flexible main chain with substituents in the form of rigid perfluorinated rods.     

Tetrafluoroethylene telomers with reactive end groups: radiation-initiated synthesis,properties, and prospects for applications

Russian Chemical Bulletin - The results of studies on radiation-initiated telomerization of tetrafluoroethylene and on the properties of telomers with reactive terminal hydroxyl, amino, and silane...     

Spectral Characteristics and Transformations of Intermediates in Irradiated Freon 11, Freon 113, and Freon 113a

Optical absorption bands observable in Freon 11, Freon 113, and Freon 113a irradiated at 77 K were assigned to various intermediates (radical cations, radical ion pairs, and complexes of radicals with ions). The transformations of these species in thermal and photochemical reactions occurring at 77 K were studied. On the basis of experimental results, it was suggested that the radical anions of Freon 11 and Freon 113 are unstable at 77 K and the spatial distribution of the intermediates produced is inhomogeneous.     

Expedient synthesis of pyrazoles substituted with amino, hydroxyl and thioamide groups

The reaction of α,β-acetylenic γ-hydroxy nitriles with thiosemicarbazide, under mild conditions (rt, no catalyst, in 1:1 aqueous ethanol, 4-14 h), proceeds chemo-, regio- and stereoselectively to give atypically so far inaccessible tri-functionalized (amino, hydroxyl and thioamide groups) pyrazoles in 53-91% yields. The hydroxyl function is easily protected by using the corresponding acetals of the starting acetylenic hydroxy nitriles.     

Surface modification of cellulose-containing materials with solutions of tetrafluoroethylene telomers

Russian Journal of Applied Chemistry - Modification of cellulose-containing materials (wood veneer, paper) with solutions of radiationsynthesized tetrafluoroethylene telomers was studied. Treatment...     

Radiation-chemical synthesis of tetrafluoroethylene telomers and their use for preparation of thin protective fluoropolymer coatings

The specific features and possibilities of preparation of protective coatings and composite materials based on fluoromonomers using high-energy rays (⁶⁰Co γ-rays, fast electrons) were analyzed. The emphasis was placed on synthesis and application of tetrafluoroethylene telomers in acetone. The structure and properties of telomers were examined by IR and NMR spectroscopy, as well as by X-ray diffraction analysis and diathermy. The radiation initiation allows preparation of new products with a broad spectrum of functional properties and opens wider prospects for technological application of fluoromonomers.     

Radiation-initiated synthesis of tetrafluoroethylene telomers in 1,2-dibromotetrafluoroethane at a constant pressure of the monomer in the reactor

The kinetics of radiation-initiated telomerization of tetrafluoroethylene in a 1,2-dibromotetrafluoroethane solution at a constant concentration (pressure) of the monomer in the reactor was studied. The properties, molecular structure, and morphology of the telomers were studied by IR spectroscopy, scanning electron microscopy, and elemental and thermal gravimetric analyses. The synthesized telomers show promise for the development of fluoropolymeric nanocomposites and protective hydrophobic and antifriction coatings.     

Synthesis of polymers with hydroxyl end groups by atom transfer radical polymerization

Polymers prepared by atom transfer radical polymerization (ATRP) contain end groups defined by the initiator used. Alkyl halides, used as initiators, lead to polymers with an alkyl group at one end and a halide as the other chain end. Using functionalized initiators such as 2‐hydroxyethyl 2‐bromopropionate, hydroxyl groups can be directly incorporated at one polymer chain end while the other end functionality remains a halogen. The direct displacement of the halogen end groups with hydroxyl groups was unsuccessful due to side reactions such as elimination (for polystyrene) or hydrolysis of ester functions (for polyacrylate). Another approach to generate hydroxyl end groups was based on the substitution of the halogen end groups by ethanolamine. This was successful for polystyrene but additional substitution at the backbone esters was observed in polyacrylates. Multiple substitution reactions could be avoided by using 4‐aminobutanol instead of 2‐aminoethanol. Hydroxyl terminated polyacrylates were also obtained by extending the polyacrylate chain end with one allyl alcohol unit in a one‐pot process by adding an excess of allyl alcohol at the end of e polymerization of acrylate.     

Surface-grafting onto aramid powder: reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl or amino groups

The surface-grafting of polymers onto aramid, poly(p-phenylene terephthalamide), powder surface by the reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl and amino groups was investigated. The introduction of acyl chloride groups onto the aramid powder surface was achieved by the reaction of the aramid powder with adipoyl dichloride: the acyl chloride group content of the surface was estimated to be 1.14 mmol/g (0.17 mmol/m²) by elemental analysis. It was found that by the reaction of acyl chloride groups on the surface with functional polymers, such as terminal diol-type poly(propylene oxide) (PPG) and terminal diamine-type poly(dimethylsiloxane) (SDA), these polymers were grafted onto the aramid powder surface; the percentage of surface grafting of PPG and SDA onto the aramid powder was 16.7 and 22.4%, respectively. The thermogravimetric curve of PPG surface-grafted aramid powder exhibited an initial weight loss at about 250°C and a second weight loss at about 500°C. This indicated that the grafting of PPG is limited to the powder surface. The wettability of the aramid powder surface turned from hydrophobic to hydrophilic by the surface-grafting of PPG onto the surface.     

Amino acid end-group in commercial heparin. I. Determination of the number of amino and hydroxyl end groups in heparin

Three commercial heparins of different molecular weights and anticoagulant activities were dinitrophenylated (DNP) with 2,4-dinitrofluorobenzene under aqueous conditions. The absorption spectra observed for DNP heparins in a 1% NaHCO₃ solution consisted of the two absorption spectra characteristic of DNP—amino (N—DNP) and DNP—hydroxyl (O—DNP) groups. The number of N—DNP, O—DNP, and (N + O)—DNP groups were determined as well as the number of N—DNP groups per heparin chain; different values (i.e., 0.16, 0.17, and 0.55) for the latter were obtained with the three heparins. Further calculations showed that two of the heparins had approximately two (N + O)—DNP groups per chain (i.e., 2.1 and 1.8) whilst the third sample, considered to be a “cruder” heparin, had a value of 1.4.     

Preparation and properties of composites based on caramelized aluminoborosilicate fabric and tetrafluoroethylene telomers

New composites based on activated caramelized aluminoborosilicate glass fabric and radiationsynthesized tetrafluoroethylene telomer solutions were prepared, and their properties were studied. The properties of materials prepared from standard commercial and caramelized glass fabrics were compared.     

Quantum-chemical simulation of the nanostructure of colloid particles and gels of tetrafluoroethylene telomers in acetone

The telomers H(C₂F₄) _n CH₂COCH₃, where n = 3,7; their complexes with acetone molecules; and the entities composed of two complexes were calculated by the quantum-chemical method of the density functional theory using the software program Priroda. The existence of two configurations of the complexes with the bond energies of 2 to 6 kcal/mol per acetone molecule was established. The bonding of acetone molecules with the macroradical during the chain transfer reaction ensures the spatially correlated arrangement of telomers and leads to the formation of a network, which determines the internal structure of both colloid particles and the gel into which the colloid particles transform with an increase in the network density.     

New polydimethylsiloxanes with bulky end groups: synthesis and properties

Russian Chemical Bulletin - New polydimethylsiloxanes (PDMS) containing bulky end groups were obtained. The structure of all obtained compounds was confirmed by a combination of physicochemical...     

Synthesis and characterization of functional fluorinated telomers

The synthesis and characterizations of fluorinated telomers based on vinylidene fluoride (VDF) by iodine transfer polymerization (ITP) are presented. These telomers were prepared in the presence of ω‐iodoperfluorinated functional chain transfer agents, C₆F₁₃I or C₄F₉I. ITPs were initiated by thermal decomposition of bis(4‐tert‐butylcyclohexyl) peroxydicarbonate (BBCHPDC), in solution (in the presence of acetonitrile). The obtained telomers were characterized by different analyses such as elemental analyses, nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy, size exclusion chromatography, X‐ray diffraction (XRD), and finally by thermal analyses such as differential scanning calorimetry (DSC) and thermogravimetric analyses. These technical analyses enabled one to assess their chemical structures, various thermal properties, and their crystalline forms. The assignments of the characteristic signals obtained by ¹⁹F NMR spectroscopy enabled one to calculate the average degrees of polymerization (DPn) and percentages of ? CH₂CF₂I end group functionalities that depend on the initiator and the fractionation process after reaction. A good control of polymerization was shown by the absence of reversed ? CH₂CF₂? CF₂CH₂? (VDF–VDF dyads) and narrow polydispersity indices (<1.2). The XRD and DSC evidenced the influence of the chain length of the telomers on the crystallinity rate (>70%) and indicated two crystalline forms, α and β, that depended on DPn values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010