TU Darmstadt / ULB / TUbiblio

Cross-linking of functionalised siloxanes with alumatrane: Reaction mechanisms and kinetics

Ischenko, V. ; Harshe, R. ; Riedel, R. ; Woltersdorf, J. (2006):
Cross-linking of functionalised siloxanes with alumatrane: Reaction mechanisms and kinetics.
In: Journal of Organometallic Chemistry, 691 (19), pp. 4086-4091. Elsevier, ISSN 0022328X,
[Article]

Abstract

Cross-linking of functionalised polysiloxanes is an important tool to adjust their viscoelastic properties and can be achieved by the reaction with alumatrane. The cross-linking reaction has been found to proceed only with hydrolyzed alumatrane species. Siloxane model compounds with different functional groups such as alkoxy, siloxy, and hydroxy groups were considered in order to optimise the rheological properties of the polymer. The activation energy barriers of the related reactions were analysed using the density functional theory under the assumption of the presence of Al–OH groups formed by the hydrolysis of alumatrane. The cross-linking involving hydroxy groups of siloxane and hydrolyzed alumatrane has been found to have the lowest activation energy (−14 kJ/mol). As the reaction of the Si–O–Si-polymer backbone with the hydroxy groups of the hydrolyzed alumatrane turned out to have the very low activation energy of +2 kJ/mol, this type of reaction is predicted to play a key role for the cross-linking of polysiloxanes with hydrolyzed alumatrane. The involved water molecules are formed back in the course of subsequent polycondensation reactions, therefore H2O can be considered as a cross-linking catalyst in these systems.

Item Type: Article
Erschienen: 2006
Creators: Ischenko, V. ; Harshe, R. ; Riedel, R. ; Woltersdorf, J.
Title: Cross-linking of functionalised siloxanes with alumatrane: Reaction mechanisms and kinetics
Language: English
Abstract:

Cross-linking of functionalised polysiloxanes is an important tool to adjust their viscoelastic properties and can be achieved by the reaction with alumatrane. The cross-linking reaction has been found to proceed only with hydrolyzed alumatrane species. Siloxane model compounds with different functional groups such as alkoxy, siloxy, and hydroxy groups were considered in order to optimise the rheological properties of the polymer. The activation energy barriers of the related reactions were analysed using the density functional theory under the assumption of the presence of Al–OH groups formed by the hydrolysis of alumatrane. The cross-linking involving hydroxy groups of siloxane and hydrolyzed alumatrane has been found to have the lowest activation energy (−14 kJ/mol). As the reaction of the Si–O–Si-polymer backbone with the hydroxy groups of the hydrolyzed alumatrane turned out to have the very low activation energy of +2 kJ/mol, this type of reaction is predicted to play a key role for the cross-linking of polysiloxanes with hydrolyzed alumatrane. The involved water molecules are formed back in the course of subsequent polycondensation reactions, therefore H2O can be considered as a cross-linking catalyst in these systems.

Journal or Publication Title: Journal of Organometallic Chemistry
Journal volume: 691
Number: 19
Publisher: Elsevier
Uncontrolled Keywords: Siloxanes, Alumatrane, Polymer cross-linking, Reaction mechanism, Kinetics
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 20 Apr 2012 06:59
Official URL: http://dx.doi.org/10.1016/j.jorganchem.2006.06.019
Identification Number: doi:10.1016/j.jorganchem.2006.06.019
Funders: The authors gratefully acknowledge the financial support by the Deutsche Forschungsgemeinschaft (DFG), Bonn.
Export:
Suche nach Titel in: TUfind oder in Google
Send an inquiry Send an inquiry

Options (only for editors)
Show editorial Details Show editorial Details