Bionanocomposites: Differential Effects of Cellulose
Nanocrystals on Protein Diblock Copolymers
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Abstract
We investigate the effects of mixing
a colloidal suspension of
tunicate-derived cellulose nanocrystals (t-CNCs) with aqueous colloidal
suspensions of two protein diblock copolymers, EC and CE, which bear
two different self-assembling domains (SADs) derived from elastin
(E) and the coiled-coil region of cartilage oligomeric matrix protein
(C). The resulting aqueous mixtures reveal improved mechanical integrity
for the CE+t-CNC mixture, which exhibits an elastic gel network. This
is in contrast to EC+t-CNC, which does not form a gel, indicating
that block orientation influences the ability to interact with t-CNCs.
Surface analysis and interfacial characterization indicate that the
differential mechanical properties of the two samples are due to the
prevalent display of the E domain by CE, which interacts more with
t-CNCs leading to a stronger network with t-CNCs. On the other hand,
EC, which is predominantly C-rich on its surface, does not interact
as much with t-CNCs. This suggests that the surface characteristics
of the protein polymers, due to folding and self-assembly, are important
factors for the interactions with t-CNCs, and a significant influence
on the overall mechanical properties. These results have interesting
implications for the understanding of cellulose hydrophobic interactions,
natural biomaterials and the development of artificially assembled
bionanocomposites