Deformation of poly(dimethylsiloxane) oligomers under uniaxial tension: Quantum chemical view

Journal of Physical Chemistry A

Volumn 103, Issue 51, 1999, Pages 11355-11365

  Nikitina, E A ^a   Khavryutchenko, V D ^b   Sheka, E F ^c   Barthel, H ^d   Weis, J ^d  

^a INSTITUTE OF APPLIED MECHANICS   (Russian Federation)

^b INSTITUTE OF SURFACE CHEMISTRY   (Ukraine)

^c PEOPLES FRIENDSHIP UNIVERSITY OF RUSSIA   (Russian Federation)

^d WACKER CHEMIE AG   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0002690806     PISSN: 10895639     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp990221v     Document Type: Article

References (40)

1. Mark, J. E.; Erman, B. Rubberlike elasticity; Wiley: New York, 1988.
2. Tashiro, K. Prog. Polym. Sci. 1993, 18, 377.
3. Klei, H. E.; Stewart, J. P. Int. J. Quantum Chem. Symp. 1986, 230, 529.
4. Wierschke, S. G. Mater. Res. Soc. Symp. Proc. 1989, 134, 313.
5. Bordeaux, D. S. J. Polym. Sci., Polym. Phys. Ed. 1973, 11, 1285.
6. Yushchenko, V. S.; Ponomareva, T. P.; Shchukin, E. D. J. Mater. Sci. 1992, 27, 1659.
7. Yushchenko, V. S.; Shchukin, E. D.; Hotokka, M. J. Mater. Sci. 1993, 28, 920.
8. Khavryutchenko, V.; Nikitina, E.; Malkin, A.; Sheka, E. Phys. Low-Dimens. Struct. 1995, 6, 65.
9. Khavryutchenko, V. D.; Khavryutchenko, A. V., Jr. DYQUAMECH, Dynamical-Quantum Modelling in Mechanochemistry Software for Personal Computers; Institute of Surface Chemistry, National Academy of Science of Ukraine: Kiev, 1993.
10. Zhurkov, S. N.; Vettegren, V. I.; Korsukov V. E.; Novak I. I. Fracture 1965, 545.
11. Kuzminski, A. S.; Sedov, V. V. Khimicheskie prevrashchenia elastomerov (Chemical Transformations of Elastomers); Khimia: Moskwa, 1984.
12. Pluvinage, G. Machanique Elastoplastique de la Rupture; Cepad: Tuluse, 1989.
13. Bartenev, G. M. Prochnost i mekhanizin razrushenia polimerov (Strength and Destruction Mechanism of Polymers); Khimia: Moskwa, 1984.
14. Stepanov, V. A.; Peschanskaya, N. N.; Shpeyzman, V. V. Prochnost i relaksacionnye javlenia v tverdykh telakh (Strength and Relaxation Phenomena in Solids); Nauka: Leningrad, 1984.
15. Gutman E. M. Mekhanokhimia metallov i zashchita ot korrosii (Mechanochemisrty of Metals and Protection from Corrosion); Metallurgia: Moskwa, 1974.
16. Baranbojm, N. K. Mekhanokhimia vysokomolkulyarnykh soedinenij (Mechanochemistry of High-Molecular Compounds); Khimia: Moskwa, 1978.
17. Avvakumov, E. G. Mekhanicheskie metody aktivacii khimicheskich processov (Mechanical Ways for Chemical Process Activation); Nauka: Novosibirsk, 1979.
18. Tobolski, A.; Eyring, H. J. Chem. Phys. 1943, 11, 125.
19. Dewar, M. J. S. Fortschr. Chem. Forsch. 1971, 23, 1.
20. Khavryutchenko, V. D.; Khavryutchenko, A. V., Jr. DYQUAMOD, Dynamical-Quantum Modelling Software for Personal Computers; Joint Institute for Nuclear Researchs, Dubna and Institute of Surface Chemistry: National Academy of Science of Ukraine: Kiev, 1993.
21. Sheka, E. F.; Khavryutchenko, V. D.; Nikitina, E. A. Phys. Low-Dimens. Struct. 1995, 1, 1.
22. Ignatjev, I. S.; Tenisheva, T. F. Kolebatelnye spectry i elektronnoje stroenie molekul s uglerod-kislorodnymi i kremnij-kislorodnymi suyasyami (Vibrational Spectra and Electronic Structure of Molcules with C-O and Si-O bonds); Nauka: Leningrad, 1991.
23. Pulay, P. Theor. Chim. Acta 1979, 50, 299.
24. Clark, T. A Handbook of Computational Chemistry. A Practical Guide to Chemical Structure and Energy Calculations; Wiley-Interscience: New York, 1985.
25. Stewart, J. P. J. Comput. Chem. 1989, 10, 209, 221.
26. The molecular force field has been obtained quantum chemically and then corrected in the course of the inverse spectral problem solution to fit precisely the experimental vibrational spectra of the molecule recorded by IR transmission and inelastic neutron scattering: Sheka, E. F.; Khavryutchenko, V. D.; Nikitina, E. A.; Natkaniec, I.; Barthel, H.; Weiss, J. Proceedings of the German Russian Users Meeting. Condense Matter Physics with Neutrons at IBR-2; Frank Laboratory of Neutron Physics, JINR: Dubna, 1998;p 122.
27. Since the bond breaking disjoins electrons of atoms involved in the bond, a question arises of whether the closed-shell approximation used throughout the paper is valid for the bond rupture description. As shown in the current study, the approximation correctly describes space structure and heat of formation of the molecule under deformation at every step, including the bond rupture. However, at the very point of the bond breaking, it fails in describing the quantities related to the electron density matrix since it does not distinguish α and β spins. This makes difficult a proper characterization of final products of the reaction. To remove the difficulty, the values given in Table I were obtained in the open-shell approximation of the PM3 technique (for reference, see: HyperChem. Computational Chemistry; Hypercube, Inc.: Waterloo, 1994; Part 2). As in the case of the closed-shell one, a spin-singlet configuration of the molecular electronic state was considered only.
28. Semenov, S. G. In Razvitije uchenia o valentnosti (Evolution of the Valency Doctrine); Khimia: Moskva, 1977; p 117.
29. Wiberg, K. B. Tetrahedron 1968, 24, 1083.
30. Khavryutchenko, V.; Sheka, E.; Aono, M.; Huang, D. H. Phys. Low-Dimens. Struct. 1996 11/12, 1.
31. Coulson, C. A. Valence, 2nd ed.; Oxford University Press: New York, 1961.
32. Khavryutchenko, V.; Sheka, E.; Aono, M.; Huang, D. H. Phys. Low-Dimens. Struct. 1998, 3/4, 81.
33. Berstein, V. A. Mechanogidroliticheskie processy i prochnost tverdykh tel (Mechanohydrolitic Processes and Strength of Solids); Nauka: Leningrad, 1987.
34. Data obtained at Wacker Chemie GmbH.
35. Sometimes, the rubber-like high elasticity is presented as an entropy-driven process while the elastic and plastic regions are connected with changes in enthalpy. This picture correlates well with the vibration-dynamical presentation discussed in section 2. Actually, the entropy is the most essential when the related enthalpy is small. These conditions are met at Stages 1 and 2 of the deformational process considered. As is known (Dewar, M. J. S.; Ford, G. J. Am. Chem. Soc. 1977, 99, 7822), the most valuable contribution to the entropy of a molecular system is provided by the lowest frequency vibrations, which are presented by torsions and bendings in the studied case.
36. Enziklopedia polimerov (Polymer Enciclopedia); Sovetskaja enciklopedia: Moskwa, 1974; t.2, p 230.
37. Tashiro, K.; Kobayashi, M. Polymer 1991, 32, 454.
38. 1
39. -1 for the C-C and Si-O bonds, respectively. The ratio of squared frequencies, which determines the ratio of the corresponding Young's moduli, ranges between 1.5 and 2.5. As seen from Tables 2 and 3, the calculated E values provide the ratios falling into the interval of 1.5-2.74, which is perfectly consistent with the above-mentioned data.
40. It should be taken into account as well that, unlike the majority of organic polymers, silicone polymers are cross-linked, which may provide additional ways for the polymers to be strengthened.