Poly(vinylidene fluoride)
(PVDF)/graphene oxide (GO) nanocomposite
fibers were dry-jet wet spun at the GO concentrations of 0, 1, and
2 wt % with respect to the polymer. The as-spun fibers were drawn
in the draw ratio (DR) range of 2–6.5, and the correlation
between the PVDF chain conformation and the mechanical properties
of the fibers upon drawing has been studied by two-dimensional correlation
spectroscopy of Fourier-transformed infrared, wide-angle X-ray diffraction,
differential scanning calorimetry, and tensile testing. The PVDF/GO
nanocomposite fibers exhibited that the mobile PVDF crystals due to
the conformational defects and kinks were nucleated because of the
polar interaction between PVDF chains and functional groups of GO,
whereas the control PVDF fiber showed the conventional conversion
of crystal polymorphs (α and γ phases to β phase).
As a result, the nanocomposite fiber showed dramatically improved
toughness (enhanced by 1123% at a DR of 2 and 120% at a DR of 6.5)
as compared to that of the control fiber. Furthermore, the tensile
strength and modulus of the PVDF/GO (2 wt %) fiber were 394 MPa and
4.6 GPa, respectively, whereas those of the control PVDF fiber were
295 MPa and 3.9 GPa, respectively.
Over hundreds of millions of years, organisms have evolved architected structures via precise control over hierarchically assembled components, including the integration of dissimilar materials. One such example is found in the radula system of chitons, intertidal mollusks that feed on algae growing on the rock. Their radula consists of multiple rows of ultrahard teeth, each integrated with a foldable belt-like substrate via a stiff, yet flexible stylus, which is essential for efficient rasping during the feeding process. Here, we investigate the nano and micro-scale components and architectures as well as regional mechanical properties of the stylus, and their subsequent role during the rasping of Cryptochiton stelleri. Three important factors were determined to contribute to the regio-specific stiffness of the stylus: the presence of mineral components, highly oriented chitinous fibers, and a chemically cross-linked protein matrix. All these factors are varied throughout the stylus. There is a high mineral content on the trailing edge close to the tooth and a cross-linked matrix on the leading edge, both with orientational specific oriented chitin fibers that provide force transduction to the tooth. Conversely, there is a significant lack of mineral or cross-linked matrix in the proximal end as well as a low degree of fiber orientation, resulting in a flexible region that can accommodate torsion and flexure during rasping. Understanding the graded composite structure of the stylus and applying this unique design to various engineering fields such as soft robotics, biotechnology, and the medical industry, can inspire the production of high-performance materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.