Deoxyguanosine Phosphate Mediated Sacrificial Bonds
Promote Synergistic Mechanical Properties in Nacre-Mimetic Nanocomposites
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Abstract
We
show that functionalizing polymer-coated colloidal nanoplatelets
with guanosine groups allows synergistic increase of mechanical properties
in nacre-mimetic lamellar self-assemblies. Anionic montmorillonite
(MTM) was first coated using cationic poly(diallyldimethylammonium
chloride) (PDADMAC) to prepare core–shell colloidal platelets,
and subsequently the remaining chloride counterions allowed exchange
to functional anionic 2′-deoxyguanosine 5′-monophosphate
(dGMP) counterions, containing hydrogen bonding donors and acceptors.
The compositions were studied using elemental analysis, scanning and
transmission electron microscopy, wide-angle X-ray scattering, and
tensile testing. The lamellar spacing between the clays increases
from 1.85 to 2.14 nm upon addition of the dGMP. Adding dGMP increases
the elastic modulus, tensile strength, and strain 33.0%, 40.9%, and
5.6%, respectively, to 13.5 GPa, 67 MPa, and 1.24%, at 50% relative
humidity. This leads to an improved toughness seen as a ca. 50% increase
of the work-to-failure. This is noteworthy, as previously it has been
observed that connecting the core–shell nanoclay platelets
covalently or ionically leads to increase of the stiffness but to
reduced strain. We suggest that the dynamic supramolecular bonds allow
slippage and sacrificial bonds between the self-assembling nanoplatelets,
thus promoting toughness, still providing dynamic interactions between
the platelets