Quantum-chemical study of CnF2 n+2 conformers. Structure and IR spectra

Ignatieva, L. N.; Beloliptsev, A. Yu.; Kozlova, S. G.; Бузник, В. М.

doi:10.1007/s10947-005-0034-5

Cited by 18 publications

(43 citation statements)

References 16 publications

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“…Similar bands are observed in the spectrum of fine-grain PTFE [5]. It was demonstrated by the method of magnetic resonance [5] and quantum-chemical calculations [6] that the first band corresponds to the olefin end groups CF CF 2 , and the second band corresponds to rocking vibrations CF 3 groups. The presence of these bands confirms depolymerization of PTFE chains and formation of oligomers.…”

supporting

confidence: 69%

Gas-jet synthesis of silver-polymer films

Ребров

Сафонов

Тимошенко

et al. 2010

J Appl Mech Tech Phy

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A new method of gas-jet deposition of metal-polymer composites with simultaneous deposition of polymer matrices and silver clusters from two gas-dynamic sources is presented. Specific features of cluster deposition and the properties of composite films are described. Results on the antibacterial effect of silver-polymer composites on stock cultures of various bacteria are reported.Antibacterial activity of silver has been known since ancient times. The recent interest in silver agents is caused by the necessity of solving problems of antibiotic applications (habituation of microorganisms to antibiotics, deletion of useful bacterial populations, etc.). The use of media containing ions and nano-sized clusters of silver turned out to be extremely effective. Most methods of cluster synthesis are based on chemical transformation of silver nitrites to the final product containing silver clusters 5-20 nm in size. These clusters are deposited onto surfaces by various methods. Environmentally friendly "dry" vacuum technologies based on re-condensation of the initial products in vacuum are available [1, 2].The present paper describes a new method: deposition of silver clusters onto a polymer matrix from supersonic jets, as it was realized in [3,4]. One variant of this method is deposition of silver and polytetrafluoroethylene (PTFE) as a polymer matrix whose precursor is tetrafluoroethylene (C 2 F 4 ). PTFE is chosen as a matrix material owing to its high stability to thermal and chemical effects and by its biological compatibility. Implementation of the method required creation of two high-temperature sources: for formation of a high-temperature C 2 F 4 flow and for evaporation of silver in the argon environment. Simultaneous deposition of the polymer and silver clusters onto a target placed alternatively under one flow and the other was performed (Fig. 1).The precursor gas (C 2 F 4 ) acquires the initial state (stagnation parameters) in a reactor where PTFE decomposition occurs at a pressure of several millimeters of the mercury column and at a stagnation temperature T = 500-700 • C. The flow of PTFE decomposition products becomes expanded in a sonic nozzle (nozzles 3 and 10 mm in diameter were used). Deposition of the metal-polymer film is performed on the target placed into supersonic jets of C 2 F 4 and argon with silver vapors.A steady flow of a mixture of argon and silver vapors is formed by a high-temperature source at a stagnation temperature T = 900-1000 • C. The jet is formed behind a conical supersonic nozzle with a total apex angle of 54 • , throat diameter of 3 mm, and geometric Mach number M = 10.5; the distance between the nozzle and the target is L = 15-20 mm. Typical mass flows of C 2 F 4 and argon are approximately 0.1 g/sec; the mass flow of silver vapors in the argon flow is approximately 10 −4 g/sec.To find the specific features of cluster formation, we studied the influence of the distance between the nozzle and the target on the character of silver deposition with the polymer being absent.

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supporting

confidence: 69%

Gas-jet synthesis of silver-polymer films

Ребров

Сафонов

Тимошенко

et al. 2010

J Appl Mech Tech Phy

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“…Nevertheless, a number of parameters characterizing the molecular structure of small macromolecules would be also valid for polymers built from the above fragments and, moreover, lowmolecular forms (telomers, fluoro paraffins) themselves have been recently in high practical demand as coatings, nanofilms and composites [7,8]. In the latter case the problem of unambiguous and reliable interpretation of empirical data can be solved by performing quantum chemistry calculations of geometric parameters, conformation, IR-, Raman and NMR-spectra of small macromolecules comprising the polymer forming units [6,[9][10][11]. In [11][12][13] we demonstrated that within the scopes of ab initio quantum chemistry methods the calculations of the electronic structure, geometric parameters and some physical-chemical characteristics of the conformers C 13 F 26 could be performed with an acceptable accuracy.…”

Section: Introductionmentioning

confidence: 99%

“…In the latter case the problem of unambiguous and reliable interpretation of empirical data can be solved by performing quantum chemistry calculations of geometric parameters, conformation, IR-, Raman and NMR-spectra of small macromolecules comprising the polymer forming units [6,[9][10][11]. In [11][12][13] we demonstrated that within the scopes of ab initio quantum chemistry methods the calculations of the electronic structure, geometric parameters and some physical-chemical characteristics of the conformers C 13 F 26 could be performed with an acceptable accuracy. The obtained theoretical data can be useful in studying the mechanisms of radiolysis (formation of radicals, sites of chain disruption etc.)…”

Section: Introductionmentioning

confidence: 99%

Quantum chemistry studies of unbranched fluoropolymers

Ignatieva

Bouznik

2011

Journal of Fluorine Chemistry

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“…The CCCC dihedral angle was calculated to be 17 o ± 1 o from trans using this method, in good agreement with previous computational studies. 7,[9][10][11][12][13][14] In the same study, the structure of perfluoropropane (C 3 F 8 ) was…”

Section: Introductionmentioning

confidence: 92%

“…Experimental and computational studies on smaller perfluoroalkane oligomers also show the lowest energy structures to be helical, beginning with perfluorobutane (C 4 F 10 ). [5][6][7][8][9][10][11][12][13][14][15] The helical (trans), gauche, and ortho (τ ~ 90 o ) conformers of C 4 F 10 were observed by nitrogen matrixisolated IR spectroscopy. 8 Only the gauche form was observed in a microwave study, 16 with the helical form apparently having too small a dipole moment to be observable and the ortho form relaxing to the lower energy gauche form.…”

Section: Introductionmentioning

confidence: 99%

Microwave spectroscopy and characterization of the helical conformer of perfluorohexane

Bohn¹,

Fournier²,

Phan³

2010

Arkivoc

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The lowest energy conformer of perfluorohexane (C 6 F 14 ) is helical and its microwave rotational spectrum has been observed and assigned. The helicity along the carbon chain results in overall C 2 symmetry with the C 2 axis corresponding to the c-principal axis. The assignment of a c-type spectrum confirms the structure of C 6 F 14 to be helical. The rotational constants are A 824.9001(9) MHz, B 202.2195(8) MHz, and C 198.3355(10) MHz. The molecular parameters were characterized by scaling computed models by the square root of the ratio of the observed second moments to those computed. The scaled structures exactly reproduce the observed second moments. From this scaling approach, the exterior C 1 C 2 C 3 C 4 dihedral angle is 16.

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Quantum-chemical study of CnF2 n+2 conformers. Structure and IR spectra

Cited by 18 publications

References 16 publications

Gas-jet synthesis of silver-polymer films

Gas-jet synthesis of silver-polymer films

Quantum chemistry studies of unbranched fluoropolymers

Microwave spectroscopy and characterization of the helical conformer of perfluorohexane

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