ISSN:
1573-4846
Keywords:
titanosiloxanes
;
siloxanes
;
hydrolysis
;
condensation
;
structural units
;
NMR
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The structural units in diphenylsilanediol/titanium-isopropoxide solutions with molar ratio Si:Ti between 1:0.1 and 1:5 were examined by means of 29Si and 17O NMR. The main component in solutions with molar ratio Si/Ti=1:0.1 is the chain-like octaphenyltetrasiloxanediol. With increasing Ti-isopropoxide content (1:0.25–1:05) Si−O−Ti units of the spirocyclic titanosiloxane Ti[O5Si4(C6H5)8]2 prevail in the solutions accompanied by the chain-like tetrasiloxanediol. The 29Si NMR spectra of 1:1 solutions indicate a lot of different Si containing building units with chemical shifts mainly between-40 and-46 ppm. The signals with a chemical shift between-40 and-46 ppm are probably caused by Si atoms which are connected via oxygen bridges directly (Si−O−Ti) or indirectly (Si−O−Si−O−Ti) with titanium. Contrary to the 1:1 solutions only one or two different species with Si−O−Ti units are present in high Ti-alkoxide containing solutions (1:5). 29Si and 17O NMR results reveal a quick hydrolysis of the Ti−O−Si bonds to titanium-oxo-hydroxo-polymers and phenylsiloxanediols or their isopropyl esters after the addition of water to the solutions. This separation into species only containing either Ti−O−Ti or Si−O−Si bonds can entail a decreased homogeneity of the reaction products on a molecular level.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00425971
