XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
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T1: P–29
SiCO materials obtained from cross-linked polysiloxanes differing
in architecture and contents of Si-H groups
Monika Wójcik-Bania
1,2
, Anna Nyczyk-Malinowska
2
, and Magdalena Hasik
2
1
Faculty of Geology, Geophysics and Environment Protection, AGH University of Science
and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland, e-mail: wojcikm@agh.edu.pl
2
Faculty of Materials Science and Ceramics, AGH University of Science and Technology,
Al. Mickiewicza 30, 30-059 Kraków, Poland
Polysiloxane networks, in which Si–O and Si–C bonds occur, are precursors of SiCO
ceramic materials. Silicon oxycarbides are analogues of amorphous silica in which some of the
divalent oxygen atoms have been replaced by tetravalent carbon atoms [1]. In stoichiometric
silicon oxycarbides all carbon atoms are connected to silicon atoms, whereas, in most of the
SiCO materials studied, excess carbon as the free phase is observed [2]. Both, stoichiometric
SiCO and those containing the free carbon phase are called silicon oxycarbides or black glasses
due to the amorphous structure and black color [3].
In the present work, cross-linked polysiloxanes of various architectures and content of Si-H
groups have been studied as precursors to SiCO materials. Poly(methylhydrosiloxane) (PMHS),
with hydrogen atom at each silicon atom in the polymer chain, was cross-linked with three
vinylsiloxanes. Linear, difunctional 1,3-divinyltetramethyldisiloxane (
Vi
MM
Vi
), cyclic,
tetrafunctional 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclo-trisiloxane (D
4
Vi
) and branched,
tetrafunctional tetrakis(vinyldimethylsiloxy)silane (QM
Vi
4
) served as cross-linking agents. The
hydrosilylation reaction was carried out in the presence of Karstedt catalyst at three molar ratios
of Si-H groups to Si-CH=CH2: 1.5:1, 3:1 and 6:1. The cross-linked polymers were pyrolyzed in
a quartz tube furnace in the flowing Ar atmosphere at 1000°C.
FTIR spectra of the pyrolysis products are typical of SiCO ceramics and contain only the
bands related to vibrations of Si–O and Si–C bonds. Yields of ceramics formed upon pyrolytic
transformation of the studied PMHS systems depend on the type of cross-linking agent applied
and the molar ratio of the reactive groups at which crosslinking was conducted. XRD
measurements have revealed that the samples subjected to pyrolysis are amorphous materials,
but a broad peak with low intensity centered at 2θ angle equal to ~25° (CuKα radiation), which
can be assigned to a lamellar structure, such as graphitic carbon, is present in the XRD patterns
of the studied pyrolyzed PMHS networks. Raman investigations of the pyrolyzed materials
confirmed the presence of free carbon in the systems. Carbon domain sizes were calculated
based on the deconvoluted Raman spectra.
Keywords: PMHS networks; Si-H groups; SiCO materials
Acknowledgment
The work was financed by Polish National Science Center (NCN) project number 014/13/B/ST5/01924 and
partially by Faculty of Geology, Geophysics and Environment Protection, AGH Dean’s Grant number
15.11.140.994.
References
[1] C. G. Pantano, A. K. Singh, H. Zhang, J. Sol-Gel Sci. Technol. 14 (1999) 7.
[2] H. Bréquel, J. Parmentier, S. Walter, R. Badheka, G. Trimmel, S. Masse, J. Latournerie, P. Dempsey,
C. Turquat, A. Desmartin-Chomle, L. Le Neindre-Prum, U. A. Jayasooriya, D. Hourlier, H.-J. Kleebe,
G. D. Sorarù, S. Enzo, F. Babonneau, Chem. Mater. 16 (2004) 2585.
[3] G. A. Zank, Preceramic polymer – derived silicon oxycarbides. In: R.G Jones, W. Ando, J.
Chojnowski, editors, Silicon-Containing Polymers. The Science and Technology of Their
Synthesis and Applications, Kluwer Academic Publ., Dordrecht 2000.
XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
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T1: P–30
Polysiloxane-silazane networks as supports for metallic platinum
Justyna Olejarka
1
, Magdalena Hasik
1
, Joanna Strzezik
2
, Mateusz Marzec
3
,
Andrzej Bernasik
4
, and Monika Wójcik-Bania
5
1
Faculty of Materials Science and Ceramics, AGH-University of Science and Technology, Poland,
e-mail: olejarka@agh.edu.pl
2
Faculty of Chemistry, Silesian University of Technology, ul. ks. M. Strzody 9, 44-100 Gliwice,
Poland
3
Academic Centre for Materials and Nanotechnology, AGH-University of Science and Technology,
Al. Mickiewicza 30, 30-059 Kraków, Poland
4
Faculty of Physics and Applied Computer Sciences, AGH-University of Science and Technology,
Al. Mickiewicza 30, 30-059 Kraków, Poland
5
Faculty of Geology, Geophysics and Environment Protection, AGH-University of Science and
Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland
Metallic platinum is an effective catalyst of a wide range of chemical processes. Incorporation of
metals into polymeric networks has been attracting attention. These hybrid materials can be used e.g.
as catalysts.
In the present work platinum particles were immobilized in the cross-linked
poly(methylhydrosiloxane). Networks were obtained by hydrosilylation reaction between -Si-H
groups of the polymer and vinyl groups of the cross-linking agent. 1,1,3,3-tetramethyl- 1,3-
divinyldisilazane was used as the cross-linking agent. Three different molar ratios of Si-H groups to
vinyl groups were applied in the process. Reaction was conducted in the inert atmosphere (Ar) at
60oC for 24 hours. Karstedt catalyst was applied. Then platinum was incorporated into the prepared
systems. The process was conducted in two different ways - from the solution of platinum(IV)
chloride in tetrahydrofuran and from the solution of dimethyl(1,5-cyclooctadiene) platinum(II) (COD)
in toluene. Incorporation of platinum from PtCl
4
was conducted in the inert atmosphere at room
temperature and controlled by UV-Vis spectroscopy. Incorporation of platinum from COD was
carried out in the inert atmosphere at the temperature of 80°C for 24 hours.
The obtained materials were characterized by several methods. For the initial networks swelling
measurements were performed. Based on the results of these experiments it was established that the
prepared polysiloxane-silazane networks showed various cross-linking degrees. FTIR spectroscopy
showed that Pt
4+
ions were reduced by the excessive Si-H groups remaining in the systems. Using X-
ray diffraction measurements it was found that Pt incorporation processes is connected with the
reduction of Pt
4+
to Pt
0
. Scanning electron microscopy (SEM) showed morphology of the obtained
materials. BSE investigations showed platinum particles dispersion on the surface of the polymer
supports. X-ray florescence measurements allowed determining contents of palladium in the prepared
systems. X-ray photoelectron spectroscopy measurements were performed. Catalytic properties were
verified by test reaction - conversion of isopropyl alcohol. It was found that all the examined systems
exhibit mainly redox activity in catalytic tests.
The study shows that polysiloxane-silazane networks can be successfully used as supports for
platinum particles. Furthermore the obtained Pt-supports are active redox catalysts.
Keywords: polysiloxane; polysilazane; platinum
Acknowledgment
The work was financially supported by the Polish National Science Centre (NCN) grant No.
2014/13/B/ST5/01924
References
[1] P. Bhanu, S. Chauhan, B. Balagam, Macromolecules 39 (2006) 2010.
[2] P. Bhanu, S. Chauhana, A. Sarkara, M. Chauhanb, A. Rokab, Appl. Organometal. Chem. 23 (2009) 385.
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