Enhancing flexible hybrid silica aerogels: integrating new functionality through addition of different precursors

Abstract

Hybrid silica aerogels can overcome one of the main drawbacks of classical silica aerogels, which are unsuitable for many industrial applications due to their brittle network. By modifying the synthesis through changes in the sol-gel, drying or post-treatment processes, different properties like the mechanical flexibility can be enhanced. This was done by Hayase in 2011 through addition of one or two methylgroups to the tetravalent Si-precursors, resulting in flexible silica aerogels known as marshmallows. These are used as basis for further improvements and modifications, allowing the investigation towards more potential uses. By modifying different parts of the synthesis, changes on a chemical and physical level can be introduced. In this work, we went from Hayase's binary to a ternary precursor system. One component investigated was tetraethoxysilane (TEOS), often used for classical silica aerogels, with the goal reduce the overall pore sizes, changing the aerogels behavior. This however comes at the expense of flexibility. Another precursor with potential for functionalization is vinylmethyldimethoxysilane (VMDMS). The vinyl- groups allow the binding of additional molecules through radical polymerization, giving rise to the possibility to create hybrids otherwise not possible.