Strengthening silica aerogels with surface initiated ATRP cross-linked poly(methyl methacrylate)

• Aerogels based on silica surface modified with cross-linked poly(methyl methacrylate) were prepared.
• Surface initiated atom transfer polymerization (ATRP) of methyl methacrylate and ethylene glycol dimethacrylate was used.
• Super critical carbon dioxide drying resulted in high surface area aerogels.
• ATRP modified aerogels were substantially stronger than un-modified aerogels.

Silica aerogels were strengthened by surface initiated atom transfer radical polymerization (SI-ATRP) of methyl methacylate (MMA) and ethylene glycol dimethacrylate (EGDMA) from ATRP initiators grafted to the gel before supercritical drying. Tetramethoxysilane (TMOS) was copolymerized in methanol with 2.67 mol% of the ATRP initiator, 3-(triethoxysilyl)propyl-2-bromo-2-methylpropanoate, to afford gels. After replacing the methanol with toluene and adding copper catalyst, MMA and EGDMA (1:1), highly cross-linked poly(MMA-co-EGDMA) was grown from the surface of the aggregated particles making up the gel. After supercritical carbon dioxide drying, the result was highly porous poly(MMA-co-EGDMA)-silica aerogel composites that were significantly stronger than silica aerogels or poly(MMA)-silica aerogel composites of the same density.