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Mechanically Robust 3D Nanostructure Chitosan-Based Hydrogels with Autonomic Self-Healing Properties
journal contribution
posted on 2016-09-19, 00:00 authored by Ali Reza Karimi, Azam KhodadadiFabrication of hydrogels based on
chitosan (CS) with superb self-healing behavior and high mechanical
and electrical properties has become a challenging and fascinating
topic. Most of the conventional hydrogels lack these properties at
the same time. Our objectives in this research were to synthesize,
characterize, and evaluate the general properties of chitosan covalently
cross-linked with zinc phthalocyanine tetra-aldehyde (ZnPcTa) framework.
Our hope was to access an unprecedented self-healable three-dimensional
(3D) nanostructure that would harvest the superior mechanical and
electrical properties associated with chitosan. The properties of
cross-linker such as the structure, steric effect, and rigidity of
the molecule played important roles in determining the microstructure
and properties of the resulting hydrogels. The tetra-functionalized
phthalocyanines favor a dynamic Schiff-base linkage with chitosan
to form a 3D porous nanostructure. Based on this strategy, the self-healing
ability, as demonstrated by rheological recovery and macroscopic and
microscopic observations, is introduced through dynamic covalent Schiff-base
linkage between NH2 groups in CS and benzaldehyde groups
at cross-linker ends. The hydrogel was characterized using FT-IR,
NMR, UV/vis, and rheological measurements. In addition, cryogenic
scanning electron microscopy (cryo-SEM) was employed as a technique
to visualize the internal morphology of the hydrogels. Study of the
surface morphology of the hydrogel showed a 3D porous nanostructure
with uniform morphology. Furthermore, incorporating the conductive
nanofillers, such as carbon nanotubes (CNTs), into the structure can
modulate the mechanical and electrical properties of the obtained
hydrogels. Interestingly, these hydrogel nanocomposites proved to
have very good film-forming properties, high modulus and strength,
acceptable electrical conductivity, and excellent self-healing properties
at neutral pH. Such properties can be finely tuned through variation
of the cross-linker and CNT concentration, and as a result these structures
are promising candidates for potential applications in various fields
of research.
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FT-IRcovalent Schiff-base linkageUVAutonomic Self-Healing Properties Fabricationtetra-functionalized phthalocyanines favorMechanically Robust 3 D Nanostructure Chitosan-Based HydrogelsCSNMR3 Dzinc phthalocyanine tetra-aldehydehydrogelchitosan covalently cross-linkedCNTNH 2 groupscryogenic scanning electron microscopy
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