Study of Polycondensation of Tetraethoxysilane Catalyzed with Dibutylbis[1-oxo(dodecyl)oxy]stannane Using 1H NMR and 29Si NMR Spectrometry and Quasi Elastic Light Scattering

[img]PDF - Authorized users only
Language: English
104Kb
Title:Study of Polycondensation of Tetraethoxysilane Catalyzed with Dibutylbis[1-oxo(dodecyl)oxy]stannane Using 1H NMR and 29Si NMR Spectrometry and Quasi Elastic Light Scattering
Creators:
Brus, Jiří
Kotlík, Petr
Karhan, Jiří
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 62, 3, pp. 442-456
Uncontrolled Keywords:QELS, NMR, <sup>1</sup>H, <sup>29</sup>Si, <sup>29</sup>Si CP/MAS, Dibutylbis[1-oxo(dodecyl)oxy]stannane, Sol-gel polycondensation, Tetraethoxysilane

Abstract

The polycondensation of tetraethoxysilane (TEOS) catalyzed with dibutylbis[1-oxo(dodecyl)oxy]stannane (dibutyltin dilaurate, DBTDL) has been investigated with the help of <sup>1</sup>H and <sup>29</sup>Si NMR spectrometry and quasi elastic light scattering (QELS). It has been found that in contrast to the acid catalyzed polycondensation the siloxane chain grows in linear and branched way, the proportion of cyclization reactions being slight. The rate of chain growth is relatively high, which is indicated by the impossibility to detect the presence of shorter oligomers in the reaction mixture by means of <sup>29</sup>Si NMR. The found rate constant of polycondensation of TEOS catalyzed with DBTDL is <i>k</i> = 0.052 dm<sup>6</sup> min<sup>-1</sup> mol<sup>-1</sup>. From the determined condensation degree at the gelation point (0.20-0.35) and the ratio of consumed amount of ethoxysilane units to the consumed amount of monomer at the gelation point (0.49-0.69) it follows that the gel is predominantly formed by cross-linking of branched macromolecules, the reaction mixture containing no distinct proportions of polycyclic and highly condensed structural units. The density of network of the gel formed is relatively low, which was proved by <sup>29</sup>Si CP/MAS NMR spectra of the solid gels. Investigation of QELS of the reaction mixture showed that the relatively large particles, microgels, were formed practically immediately after the reaction had started. The presence of such particles in the reaction mixture of acid catalyzed polycondensation of TEOS was not proved.

Title:Study of Polycondensation of Tetraethoxysilane Catalyzed with Dibutylbis[1-oxo(dodecyl)oxy]stannane Using 1H NMR and 29Si NMR Spectrometry and Quasi Elastic Light Scattering
Creators:
Brus, Jiří
Kotlík, Petr
Karhan, Jiří
Uncontrolled Keywords:QELS, NMR, <sup>1</sup>H, <sup>29</sup>Si, <sup>29</sup>Si CP/MAS, Dibutylbis[1-oxo(dodecyl)oxy]stannane, Sol-gel polycondensation, Tetraethoxysilane
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:62
Number:3
Page Range:pp. 442-456
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19970442UNSPECIFIED
ID Code:1129
Item Type:Article
Deposited On:06 Feb 2009 17:06
Last Modified:06 Feb 2009 16:06

Citation

Brus, Jiří; Kotlík, Petr; Karhan, Jiří (1997) Study of Polycondensation of Tetraethoxysilane Catalyzed with Dibutylbis[1-oxo(dodecyl)oxy]stannane Using 1H NMR and 29Si NMR Spectrometry and Quasi Elastic Light Scattering. Collection of Czechoslovak Chemical Communications, 62 (3). pp. 442-456. ISSN 0010-0765

Repository Staff Only: item control page