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

详细信息    查看全文

• 作者：V. Ischenko ; R. Harshe ; R. Riedel and J. Woltersdorf
• 关键词：Siloxanes ; Alumatrane ; Polymer cross-linking ; Reaction mechanism ; Kinetics
• 刊名：Journal of Organometallic Chemistry
• 出版年：2006
• 出版时间：15 September 2006
• 年：2006
• 卷：691
• 期：19
• 页码：4086-4091
• 全文大小：264 K

文摘

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.