Biobased circular
materials are alternatives to fossil-based engineering
plastics, but simple and material-efficient synthetic routes are needed
for industrial scalability. Here, a series of lignin-based vitrimers
built on dynamic acetal covalent networks with a gel content exceeding
95% were successfully prepared in a one-pot, thermally activated,
and catalyst-free “click” addition of softwood kraft
lignin (SKL) to poly(ethylene glycol) divinyl ether (PDV). The variation
of the content of lignin from 28 to 50 wt % was used to demonstrate
that the mechanical properties of the vitrimers can be widely tuned
in a facile way. The lowest lignin content (28 wt %) showed a tensile
strength of 3.3 MPa with 35% elongation at break, while the corresponding
values were 50.9 MPa and 1.0% for the vitrimer containing 50 wt %
of lignin. These lignin-based vitrimers also exhibited excellent performance
as recoverable adhesives for different substrates such as aluminum
and wood, with a lap shear test strength of 6.0 and 2.6 MPa, respectively.
In addition, recyclability of the vitrimer adhesives showed preservation
of the adhesion performance exceeding 90%, indicating a promising
potential for their use in sustainable circular materials.
Material design using nonequilibrium systems provides straightforward access to complexity levels that are possible through dynamic processes. Pattern formation through nonequilibrium processes and reaction–diffusion can be used to achieve this goal. Liesegang patterns (LPs) are a kind of periodic precipitation patterns formed through reaction–diffusion. So far, it has been shown that the periodic band structure of LPs and the geometry of the pattern can be controlled by experimental conditions and external fields (e.g., electrical or magnetic). However, there are no examples of these systems being used to retrieve information about the changes in the environment as they form, and there are no studies making use of these patterns for complex material preparation. This work shows the formation of LPs by a diffusion–precipitation reaction in a stretchable hydrogel and the control of the obtained patterns by the unprecedented and uncommon method of mechanical input. Additionally, how to use this protocol and how deviations from “LP behavior” of the patterns can be used to “write and store” information about the time, duration, extent, and direction of gel deformation are presented. Finally, an example of using complex patterning to deposit polypyrrole by using precipitation patterns is shown as a template.
Weak interfacial binding of lignin within synthetic polymer composites results in unsatisfactory mechanical properties that limit their application prospects. In the present work, polystyrene (PS) and poly(butyl methacrylate) (PBMA) nanocomposites...
Spherical lignin nanoparticles are emerging biobased nanomaterials, but instability and dissolution in organic solvents and aqueous alkali restrict their applicability. Here, we report the synthesis of hydroxymethylated lignin nanoparticles and their hydrothermal curing to stabilize the particles by internal cross-linking reactions. These colloidally stable particles contain a high biobased content of 97% with a tunable particle size distribution and structural stability in aqueous media (pH 3 to 12) and organic solvents such as acetone, ethanol, dimethylformamide, and tetrahydrofuran. We demonstrate that the free phenolic hydroxyl groups that are preserved in the cured particles function as efficient reducing sites for silver ions, giving rise to hybrid lignin−silver nanoparticles that can be used for quick and facile sensing of hydrogen peroxide. The stabilized lignin particles can also be directly modified using base-catalyzed reactions such as the ring-opening of cationic epoxides that render the particles with pHdependent agglomeration and redispersion properties. Combining scalable synthesis, solvent stability, and reusability, this new class of lignin nanoparticles shows potential for its use in circular biobased nanomaterials.
Sustainable materials
are needed to mitigate against the increase
in energy consumption resulting from population growth and urbanization.
Here, we report fully biobased nanocomposite films and coatings that
display efficient photothermal activity and selective absorption of
ultraviolet (UV) radiation. The nanocomposites with 20 wt % of lignin
nanoparticles (LNPs) embedded in a chitosan matrix displayed an efficient
UV blocking of 97% at 400 nm along with solar energy-harvesting properties.
The reflectance spectra of the nanocomposite films revealed the importance
of well-dispersed nanoparticles in the matrix to achieve efficient
UV-blocking properties. Finally, yet importantly, we demonstrate the
nanocomposites with 20 wt % LNPs as photothermal glass coatings for
passive cooling of indoor temperature by simply tailoring the coating
thickness. Under simulated solar irradiation of 100 mW/cm2, the 20 μm coating achieved a 58% decrease in the temperature
increment in comparison to the system with uncoated glass. These renewable
nanocomposite films and coatings are highly promising sustainable
solutions to facilitate indoor thermal management and improve human
health and well-being.
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