The electrochemical and charge storage properties of different lignins inside biopolymer electrodes were studied and correlated with the chemical variations of the lignins as indicated from the nuclear magnetic resonance (NMR) spectroscopic data. The varying fractions of monolignols were found to correlate with charge storage properties. It was found that as the sinapyl to guaiacyl (S/G) ratio increased both the specific capacitance and charge capacity increased considerably. This indicates that quinones generated on S-units can contribute more to charge storage in the biopolymer electrodes.
Lignin derivatives, which arise as waste products from the pulp and paper industry and are mainly used for heating, can be used as charge storage materials. The charge storage function is a result of the quinone groups formed in the lignin derivative. Herein, we modified lignins to enhance the density of such quinone groups by covalently linking monolignols and quinones through phenolation. The extra guaiacyl, syringyl, and hydroquinone groups introduced by phenolation of kraft lignin derivatives were monitored by (31) P nuclear magnetic resonance and size exclusion chromatography. Electropolymerization in ethylene glycol/tetraethylammonium tosylate electrolyte was used to synthesize the kraft lignin/polypyrrole hybrid films. These modifications changed the phenolic content of the kraft lignin with attachment of hydroquinone units yielding the highest specific capacity (around 70 mA h g(-1) ). The modification of softwood and hardwood lignin derivatives yielded 50 % and 23 % higher charge capacity than the original lignin, respectively.
of the monolignols syringol (S) and guaiacol (G) were prepared as welldefined lignin model compounds. Polymerisation was performed by phenol-formaldehyde condensation, also including the monomer hydroquinone (HQ) to extend the range of redox processes in these synthetic lignins (SLig). The chemical structures of the SLig samples were characterized by 13 C and quantitative 31 P NMR, and the molecular weight was monitored by size exclusion chromatography (SEC). Subsequently, SLig were incorporated into two different electron-conducting matrixsingle-wall carbon nanotubes (SWNT) and polypyrrole (PPy), respectively. As a result, the hybrid materials, with a controlled amount of SWNT or with an unknown amount of PPy, were assembled and compared. The charge storage properties in the investigated materials are attributed to contributions from both the double-layer capacitance of the conducting matrix, and the faradaic reactions provided by quinone groups immobilized in the electrodes. The results indicate a considerable improvement of charge capacity, with the synthetic lignins incorporated in the hybrid materials. With a PPy carrying S, G and HQ, better performance is obtained than has previously been obtained with lignin derivatives, showing a maximum capacity of 94 mA h g À1 . Moreover, a low amount of electronic conductor (20% wt of SWNT) is adequate to perform efficient electron communication between redox active quinones and the electrode surface, providing 72 mA h g À1 .
Production
of fibers from nonthermoplastic polymers, such as chitosan,
usually requires dissolution with subsequent fiber formation, for
instance, via coagulation. Good fiber-forming properties enable simultaneous
spinning of multiple fibers into a yarn, which is one of the prerequisites
for process scalability. Here, we report a multifilament wet-spinning
process that eliminates the use of such volatile organic compounds
as methanol and acetone, enhances fiber formation, and allows producing
continuous well-separated chitosan fibers after drying. This is achieved
by (i) solidification of the extruded solution by alkali and sodium
acetate in the coagulation bath and (ii) further stabilization of
the fibers by adsorbing the anionic surfactant, sodium dodecyl sulfate.
The obtained fibers have a circular cross section and smooth surface.
We demonstrate that it is possible to increase fiber breaking tenacity
and Young’s modulus by applying stretching (draw ratios up
to 1.77) or by incorporating cellulose nanofibrils (CNFs, up to 4
wt % based on chitosan) in the spinning solutions. However, the limitation
of increased viscosity when adding CNF is needed to be overcome for
possible higher reinforcement effects. We demonstrate that fiber breaking
tenacity, Young’s modulus, and elongation at break can be enhanced
even further by increasing the spin dope temperature from 22 to 60
°C, with simultaneously increasing the spin dope solid content
to keep the same dope viscosity. The fibers with a maximum breaking
tenacity of ca. 10 cN/tex at an elongation at break of ca. 7.5% were
obtained.
Functional textiles is a rapidly growing product segment in which sustained release of actives often plays a key role. Failure to sustain the release results in costs due to premature...
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