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Silk Fibroin Dissolution in Tetrabutylammonium Hydroxide Aqueous Solution
journal contribution
posted on 2019-10-15, 19:43 authored by Bruno Medronho, Alexandra Filipe, Sofia Napso, Rafail. L. Khalfin, Rui F. P. Pereira, Verónica de Zea Bermudez, Anabela Romano, Yachin CohenBombyx mori L. silk fibroin (SF) is widely used
in different areas due to its ability to form durable and resilient
materials with notable mechanical properties. However, in some of
these applications the dissolution of SF is required, and this is
not often straightforward due to its inability to be dissolved in
the majority of common solvents. This work reports a novel approach
to dissolve SF using 40 wt % aqueous tetrabutylammonium hydroxide,
TBAOH(aq), at mild temperature. A thorough rheological study combined
with small-angle X-ray scattering is presented to correlate the SF
state in solution with changes in the rheological parameters. The
scattering data suggest that the SF conformation in TBAOH(aq) is close
to a random coil, possibly having some compact domains linked with
flexible random chains. The radius of gyration (Rg) and the molecular weight (Mw) were estimated to be ca. 17.5 nm and 450 kDa, respectively, which
are in good agreement with previous works. Nevertheless, a lower Mw value was deduced from rheometry (i.e., 321
kDa) demonstrating a low degree of depolymerization during dissolution
in comparison to other harsh processes. The transition from a dilute
to a semidilute regime coincides with the estimated critical concentration
and is marked by the presence of a shear-thinning behavior in the
flow curves, violation of the empirical Cox–Merz rule, and
an upward increase in the activation energy. This work paves the way
toward the development of advanced high-tech SF-based materials.
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dissolutionSF-based materialsTetrabutylammonium Hydroxide Aqueous Solution Bombyx mori L17.5 nmsilk fibroinwork reports450 kDaR gSF staterheological studyshear-thinning behaviorTBAOHSF conformationflow curvessemidilute regimesmall-angle X-raynovel approachsilk Fibroin Dissolutionrheological parametersactivation energytetrabutylammonium hydroxide
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