Blended biocomposites created from the electrostatic and hydrophobic interactions between polysaccharides and structural proteins exhibit useful and unique properties. However, engineering these biopolymers into applicable forms is challenging due to the coupling of the material’s physicochemical properties to its morphology, and the undertaking that comes with controlling this. In this particular study, numerous properties of the Bombyx mori silk and microcrystalline cellulose biocomposites blended using ionic liquid and regenerated with various coagulation agents were investigated. Specifically, the relationship between the composition of polysaccharide-protein bio-electrolyte membranes and the resulting morphology and ionic conductivity is explored using numerous characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray scattering, atomic force microscopy (AFM) based nanoindentation, and dielectric relaxation spectroscopy (DRS). The results revealed that when silk is the dominating component in the biocomposite, the ionic conductivity is higher, which also correlates with higher β-sheet content. However, when cellulose becomes the dominating component in the biocomposite, this relationship is not observed; instead, cellulose semicrystallinity and mechanical properties dominate the ionic conduction.
In this study, the
structural, thermal, and morphological properties
of biocomposite films composed of wool keratin mixed with cellulose
and regenerated with ionic liquids and various coagulation agents
were characterized and explored. These blended films exhibit different
physical and thermal properties based on the polymer ratio and coagulation
agent type in the fabrication process. Thus, understanding their structure
and molecular interaction will enable an understanding of how the
crystallinity of cellulose can be modified in order to understand
the formation of protein secondary structures. The thermal, morphological,
and physiochemical properties of the biocomposites were investigated
by Fourier transform infrared (FTIR) spectroscopy, scanning electron
microscopy (SEM), thermal gravimetric analysis (TGA), differential
scanning calorimetry (DSC), and X-ray scattering. Analysis of the
results suggests that both the wool keratin and the cellulose structures
can be manipulated during dissolution and regeneration. Specifically,
the β-sheet content in wool keratin increases with the increase
of the ethanol solution concentration during the coagulation process;
likewise, the cellulose crystallinity increases with the increase
of the hydrogen peroxide concentration via coagulation. These findings
suggest that the different molecular interactions in a biocomposite
can be tuned systematically. This can lead to developments in biomaterial
research including advances in natural based electrolyte batteries,
as well as implantable bionics for medical research.
Lignin’s immiscibility with most polymers along with its unknown association behaviors are major factors that contribute to its disposal and processability for the production of materials. To fully utilize lignin, an improved understanding of its interaction with other materials is needed. In this study, we investigate the morphological and physicochemical properties upon the addition of reduced graphene oxide (rGO) as a function of material composition in a tertiary system comprised of lignin, cellulose and xylan. The main motivation for this work is to understand how the lignin molecule associates and behaves in the presence of other natural macromolecules, as well as with the addition of reduced graphene oxide. The fabricated biocomposites with and without rGO were investigated using Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR), Scanning Electron Microscope (SEM) techniques, Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). The results demonstrated that the regenerated films’ structural, morphological and thermal character changed as a function of lignin-xylan concentration and upon the addition of rGO. We also observed a dramatic change in the glass transition temperature and topography. Final analysis showed that the addition of rGO prevented the macromolecules to self-assemble through a reduction of π-π aggregations and changes in the cellulose crystallinity.
Electrospinning is a widely used technique to draw recalcitrant biopolymer solutions into micro to nanoscale materials in a simple and economical way. The first focus of this research involved using ionic liquids as a non-volatile solvent for natural insoluble biopolymers such as silk and cellulose (or cellulose derivatives). Compared to traditional organic solvents, ionic liquids can dissolve biopolymers without altering the molecular weight of the biopolymer. In this study, 1-ethyl-3-methylimidizolium acetate (EMIMAc) ionic liquid was used and the regenerated films were coagulated in baths of EtOH or water. The second focus of this research explored the dissolution of IL-regenerated composites into organic solvents and their electrospun composite nanomaterials. Various ratios of silk-cellulose bio-composite films regenerated from ionic liquids were used as the raw materials and sequentially dissolved/dispersed into a Formic Acid-CaCl2 solution in order to initiate the electrospinning of silk-cellulose nanomaterials. Because of the variability of ionic liquids, the nanomaterials produced using this technique have unique and tunable properties such as large surface area to volume ratios and low structural defects. FTIR and SEM results suggest that the structure and morphology of the final nanosized samples becomes more globular when the biopolymer composition ratio has increased cellulose content. TGA results demonstrated that the electrospun materials have better thermal stability than the original films. This two-step electrospinning method, using ionic liquid as a non-volatile solvent to first dissolve and mix raw natural materials, may lead to extensive research into its biomedical and pharmaceutical applications in the future.
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