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Lignin is a promising feedstock for renewable fuels and chemicals due to its aromatic skeleton and natural abundance. Lignin can be converted to diverse aromatic monomers as well as dicarboxylic acids depending on the applied conversion technologies. Despite its great potential, its native and processing-induced heterogeneity and complexity limit the conversion efficiency and product selectivity. In this study, magnesium ferrite (MgFe2O4) nanoparticle–peracetic acid (PAA) has been investigated as an efficient catalyst–oxidant incorporation for catalytic oxidative depolymerization of lignin under mild conditions. Typically, the increase in processing severity can enhance the lignin conversion while it results in the further decomposition of aromatic compounds to dicarboxylic acids. However, in this study, the incorporation of MgFe2O4 nanoparticles and PAA not only enhanced the total product yield but also improved the selectivity of aromatic monomers. The oxidative depolymerization system using the catalyst–oxidant combination resulted in 46 wt % of total oil product with a 61% selectivity of aromatic monomers under mild temperature (90 °C). In addition, this combination catalyst showed relatively good cycling stability based on the total product yield after recycling five times via magnetic separation. Overall, MgFe2O4 nanoparticles play an important role as a co-catalyst with a PAA oxidant in the oxidative conversion of lignin with an enhanced conversion efficiency and recyclability, and it will facilitate the valorization of lignin in future bio-based fuels and chemicals. [ABSTRACT FROM AUTHOR]

Photomechanicaleffects in polymeric materials directly convertinput photonic energy into a macroscopic mechanical output. The photoinitiatedmechanical output of these materials is typically dominated by classicalmechanics, primarily derived from the material stiffness and samplegeometry. Accordingly, large magnitude shape change (e.g., motion)is typically traded for large magnitude force generation. Here, wereport on the systematic preparation and comparison of photomechanicaleffects in a set of isomerically varied linear and cross-linked azobenzene-functionalizedmaterials that demonstrate the critical role of segmental mobility(evident in the magnitude of the β-transition) to assimilatethe typically exclusive properties of large force generation and largeshape change in a single material. [ABSTRACT FROM AUTHOR]

Therheological properties of poly(3-hexylthiophene) (P3HT) solutionswere investigated in a nonvolatile solvent, 2-ethylnaphthalene, atvarious P3HT concentrations. A mild viscosity increase was noted duringshear for lower concentration P3HT solutions over 24 h, yet the viscosityincrease was greater than if the sample was not sheared at all overthe same time period. In this case, crystalline fibrils with largeaspect ratios were formed during shear. Crystallization was determinedto be dictated by Brownian motion and mediated by shear, or in otherwords Brownian motion brought the molecules together while shear changedtheir conformation to allow crystallization. Higher concentrationP3HT solutions produced a significant viscosity increase, up to 2orders of magnitude, during shear. Again, if a similar solution wasmerely aged without shear, a much lower viscosity increase was noted.Simple calculations show that the fibril concentration was above thepercolation threshold at the higher concentration accounting for thelarge viscosity increase. Finally, the crystal structure of P3HT aftershear was found to have π–π stacking (b-axis) direction parallel to the crystalline needle axis, as seenfor crystals formed under quiescent conditions, yet the crystallinefibrils are micrometers long. The proposed mechanism for crystal formationis that Brownian motion brings the molecules to a growing crystalface while shear removes improperly incorporated chains, allowinglonger crystals to form. This phenomenon is expected to apply to othersystems, allowing formation of longer, more perfect crystalline fibrils. [ABSTRACT FROM AUTHOR]

Natural melanins are biocompatible conductors with versatile functionalities. Here, we report fabrication of multifunctional poly(vinyl alcohol)/melanin nanocomposites by layer-by-layer (LBL) assembly using melanin nanoparticles (MNPs) directly extracted from sepia officinalis inks. The LBL assembly offers facile manipulation of nanotextures as well as nm-thickness control of the macroscale film by varying solvent qualities. The time-resolved absorption was monitored during the process and quantitatively studied by fractal dimension and lacunarity analysis. The capability of nanoarchitecturing provides confirmation of complete monolayer formation and leads to tunable iridescent reflective colors of the MNP films. In addition, the MNP films have durable electrochemical conductivities as evidenced by enhanced charge storage capacities for 1000 cycles. Moreover, the MNP covered ITO (indium tin oxide) substrates significantly reduced secretion of inflammatory cytokines, TNF-α, by raw 264.7 macrophage cells compared to bare ITO, by a factor of 5 and 1.8 with and without lipopolysaccharide endotoxins, respectively. These results highlight the optoelectronic device-level tunability along with the anti-inflammatory biocompatibility of the MNP LBL film. This combination of performance should make these films particularly interesting for bioelectronic device applications such as electroceuticals, artificial bionic organs, biosensors, and implantable devices.

Liquid crystalline polymers have recently been engineered to exhibit complex macroscopic shape adaptivity, including optically- and thermally driven bending, self-sustaining oscillation, torsional motion, and three-dimensional folding. Miniaturization of these novel materials is of great interest for both fundamental study of processing conditions and for the development of shape-changing microdevices. Here, we present a scalable method for high-fidelity replica molding of glassy liquid crystalline polymer networks (LCNs), by vacuum-assisted replica molding, along with magnetic field-induced control of the molecular alignment. We find that an oxygen-free environment is essential to establish high-fidelity molding with low surface roughness. Identical arrays of homeotropic and polydomain LCN microstructures are fabricated to assess the influence of molecular alignment on the elastic modulus (E = 1.48 GPa compared to E = 0.54 GPa), and side-view imaging is used to quantify the reversible thermal actuation of individual LCN micropillars by high-resolution tracking of edge motion. The methods and results from this study will be synergistic with future advances in liquid crystalline polymer chemistry, and could enable the scalable manufacturing of stimuli-responsive surfaces for applications including microfluidics, tunable optics, and surfaces with switchable wetting and adhesion.