Silica-epoxy interfaces in bicontinuous nanocomposites
File(s)
Published version
Author(s)
Shaw, Charles
Anthony, David
Hamerton, Ian
Shaffer, Milo
Type
Conference Paper
Abstract
In classic discontinuous silica-epoxy nanocomposites, strong matrix-reinforcement interactions may
enhance toughness by introducing new energy absorption mechanisms. These silica-epoxy interactions
are mediated either directly through inherent silica silanol groups or via tethering of reactive amine or
epoxide groups. Recently, bicontinuous silica-epoxy nanocomposites have been formed by backfilling
monolithic silica aerogel with epoxy resin. The continuous reinforcement network provides long-range
load transfer, inherently uniform silica distribution, and synergistic interlocking effects. When preparing
these nanocomposites, the silica aerogel is typically hydrophobised to prevent moisture absorption
which can lead to shrinkage or cracking prior to backfilling. However, the aggressive reagents used
(typically trimethylchlorosilane,TMCS) give almost complete conversion of silanol groups, leading to
an inert surface which forms only very weak interactions with epoxy resin. Under shear loading, this
poor interface leads to brittle failure at relatively low strain. Mild hydrophobisation agents such as
dimethyldimethoxysilane (DMDMS), instead give incomplete conversion of silanols to yield a “part-
methylated” surface which, while providing some hydrophobic character, forms a stronger silica-epoxy
interface. Furthermore, as it does not form acidic byproducts, which would otherwise catalyse ring
opening, DMDMS may be used alongside (3-glycidyloxypropyl)trimethoxysilane (GPTMS) to give a
“part methylated + epoxidated” surface. Across a broad range of silica aerogel densities, both surface
types give significantly lower moisture content (“part methylated” ≈ 2.6 wt.%, “part methylated +
epoxidated” ≈ 1.4 wt.%) when compared with unmodified silica aerogel (≈ 9.8 wt.%). These values are
greater than those of TMCS-methylated silica aerogel, however, in contrast to unmodified silica aerogel,
uncracked monoliths are formed in all cases.
enhance toughness by introducing new energy absorption mechanisms. These silica-epoxy interactions
are mediated either directly through inherent silica silanol groups or via tethering of reactive amine or
epoxide groups. Recently, bicontinuous silica-epoxy nanocomposites have been formed by backfilling
monolithic silica aerogel with epoxy resin. The continuous reinforcement network provides long-range
load transfer, inherently uniform silica distribution, and synergistic interlocking effects. When preparing
these nanocomposites, the silica aerogel is typically hydrophobised to prevent moisture absorption
which can lead to shrinkage or cracking prior to backfilling. However, the aggressive reagents used
(typically trimethylchlorosilane,TMCS) give almost complete conversion of silanol groups, leading to
an inert surface which forms only very weak interactions with epoxy resin. Under shear loading, this
poor interface leads to brittle failure at relatively low strain. Mild hydrophobisation agents such as
dimethyldimethoxysilane (DMDMS), instead give incomplete conversion of silanols to yield a “part-
methylated” surface which, while providing some hydrophobic character, forms a stronger silica-epoxy
interface. Furthermore, as it does not form acidic byproducts, which would otherwise catalyse ring
opening, DMDMS may be used alongside (3-glycidyloxypropyl)trimethoxysilane (GPTMS) to give a
“part methylated + epoxidated” surface. Across a broad range of silica aerogel densities, both surface
types give significantly lower moisture content (“part methylated” ≈ 2.6 wt.%, “part methylated +
epoxidated” ≈ 1.4 wt.%) when compared with unmodified silica aerogel (≈ 9.8 wt.%). These values are
greater than those of TMCS-methylated silica aerogel, however, in contrast to unmodified silica aerogel,
uncracked monoliths are formed in all cases.
Date Issued
2026-02-10
Date Acceptance
2025-05-01
Citation
2026
Publisher
The University of Delaware
Copyright Statement
Copyright © 2026 The Author(s). This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-sa/4.0/).
License URL
Source
24th International Conference on Composite Materials - Baltimore, Maryland (ICCM-24)
Publication Status
Published online
Start Date
2025-08-04
Finish Date
2025-08-08
Coverage Spatial
Baltimore, MD, USA
Date Publish Online
2026-02-10