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Cellulose II aerogels are a highly porous class of biobased ultra-light-weight materials. They consist of interlinked networks of loosely aggregated cellulose fibrils. The latter typically have random orientation due to spontaneous phase separation triggered by addition of antisolvent to moleculardisperse cellulose solutions. Deceleration of phase separation has been recently proposed as a novel approach towards aerogels featuring preferred cellulose orientation. Here, we investigate the mechanical response of such oriented cellulose aerogels towards load up to 80% compression. Stress-strain curves were recorded and in situ small angle X-ray scattering (SAXS) was performed during compression test to obtain information about the structural alterations of the aerogel fibril networks on the nano-scale related to deformation. Using SAXS in addition, structural changes can be followed in much more detail than by recording stress-strain curves alone. Buckling and coalescence of fibers and a change in fibril orientation can be related to certain regimes in the stress-strain curve. If the loading axis is oriented parallel to the network orientation the aerogels show higher resilience towards the compression.

Assembly of (bio)polymers into long-range anisotropic nanostructured gels and aerogels is of great interest in advanced material engineering since it enables directional tuning of properties, such as diffusivity, light, heat, and sound propagation, cell proliferation, and mechanical properties. Here we present an approach toward anisotropic cellulose II gels and aerogels that employs specific diffusion and phase separation phenomena occurring during decelerated infusion of an antisolvent into isotropic supercooled solutions of cellulose in an ionic liquid to effectuate supramolecular assembly of cellulose in anisotropic colloidal network structures. At the example of the distillable ionic liquid 1,1,3,3-tetramethylguanidinium acetate, the antisolvent ethanol, and spherocylindrical porous molds, we demonstrate that the proposed facile, environmental-benign and versatile route affords gels and aerogels whose specific anisotropic nanomorphology and properties reflect the preferred supramolecular cellulose orientation during phase separation, which is perpendicular to the direction of antisolvent diffusion. Comprehensive X-ray scattering experiments revealed that the (aero)gels are composed of an interconnected, fibrous, highly crystalline (CrI ≈ 72%), cellulose II with a cross-sectional Guinier radius of the struts of about 2.5 nm, and an order parameter gradient from about 0.1 to 0.2. The obtained gels and aerogels feature high specific surface areas (350-630 m 2 g -1 ) and excellent mechanical properties like high toughness (up to 471 kJ m -3 for a 60% compression, ρ B = 80 mg cm -3 ) and resilience (up to 13.4 kJ m -3 , ρ B = 65 mg cm -3 ).

• Increasing textile waste generation has risen European Union to implement regulations and strategies. • Chemo-enzymatic treatment of blended textiles enabled selective hydrolysis and removal of cellulose allowing polyester recovery. • Precise condition adjustment is crucial to avoid polyester damage and ensure complete cellulose removal. • Optimized conditions can transform the textile industry from linear to circular, reducing the amount of textile waste. • Industrial implementation realises a sustainable textile biorefinery concept. The study demonstrates the potential of enzymatic hydrolysis and alkaline pretreatment for sustainable blended textile recycling. The target is complete cellulose removal while preserving the polyester integrity for recovery. Interactions of sodium hydroxide concentration (10 %–30 %), urea concentration (0 %–12 %), and temperature (-20 °C–50 °C) were investigated during pretreatment using a design of experiments. Analysis revealed a bimodal pattern in polyester mass loss, with one peak at lower concentrations and temperatures, and a more prominent peak at higher concentrations and temperatures. Cellulose hydrolysis also occurred under high NaOH concentrations and elevated temperatures (50 °C, 30 % NaOH, 0 % urea). Optimal conditions, preserving polyester integrity while achieving complete cellulose elimination, were identified at temperatures between 6.2 °C and 13.3 °C, with NaOH concentrations of 20.7 %–26.6 % (0 % urea) or 13.9 % NaOH and 12 % urea. These findings pave the way for a greener, more efficient textile recycling, advancing the circularity for textiles. [Display omitted] [ABSTRACT FROM AUTHOR]

The impact of selected cellulose solvent systems based on the principal constituents tetrabutylammonium fluoride (TBAF), 1-ethyl-3-methyl-1 H-imidazolium-acetate, N-methylmorpholine- N-oxide, or calcium thiocyanate octahydrate (CTO) on the properties of cellulose II aerogels prepared from these solvent systems has been investigated as a means towards tailoring cellulose aerogel properties with respect to specific applications. Cotton linters were used as representative plant cellulose. Cellulose was coagulated from solutions with comparable cellulose content, and dried with supercritical carbon dioxide after solvent exchange. The resulting bulk aerogels were comprehensively morphologically and mechanically tested to relate structure and mechanical properties. Different solvent systems caused considerable differences in the properties of the bulk samples, such as internal surface area (nitrogen sorption), morphology, porosity (He pycnometry, thermoporosimetry), and mechanical stability (compression testing). The results of SAXS, WAXS, and solid-state C NMR spectroscopy suggest that this is due to different mechanisms of cellulose self-assembling on the supramolecular and nanostructural level, respectively, as reflected by the broad ranges of cellulose crystallinity, fibril diameter, fractal dimension and skeletal density. Both solid state NMR and WAXS experiments confirmed the sole existence of the cellulose II allomorph for all aerogels, with crystallinity reaching a maximum of 46-50 % for CTO-derived aerogels. Generally, higher fibril diameter, degree of crystallinity, hence increased skeletal density were associated with good preservation of shape and dimension throughout conversion of lyogels to aerogels, and enhanced mechanical stability, but somewhat reduced specific surface area. Amorphous, yet highly rigid aerogels derived from TBAF/DMSO mixtures deviated from this trend, most likely due to their particular homogeneous and nanostructured morphology. [ABSTRACT FROM AUTHOR]

Carbon particles were produced from kraft lignin through carbonization of perfectly spherical, sub-micron beads obtained by aerosol flow. The structure of the resulting carbon particles was elucidated and compared to that derived from commercially available technical lignin powder, which is undefined in geometry. In addition to the smaller diameters of the lignin beads (<1 µm) compared to those of the lignin powder (100 µm), the former displayed a slightly higher structural order as revealed by X-ray diffraction and Raman spectroscopy. With regard to potential application in composite structures, the sub-micron carbon beads were clearly advantageous as a filler of cellulose nanopapers, which displayed better mechanical performance but with limited electrical conductivity. Compression sensing was achieved for this nanocomposite system. [ABSTRACT FROM AUTHOR]

Dissolving pulp has been subjected to consecutive periodate/chlorite treatments to afford 2,3-dicarboxyl cellulose (DCC, 1.02 mmol g-1 COOH). Subsequent nanofibrillation afforded stable nematic nf-DCC dispersions (average particle size 2.1 nm x 525 nm) at significantly lower energy input compared to TEMPO-oxidation. Acid-induced gelation triggered by extensive hydrogen bonding sets the ordered state and affords free-standing hydrogels that can be converted to highly transparent birefringent aerogels by scCO2 drying. Uniaxial compression of the obtained ultra-lightweight ductile nf-DCC aerogels down to 5% of their original volume intriguingly preserves nematic orientation and transparence. Simultaneously, strain hardening translates into exceptionally good mechanical properties, such as toughness at nearly zero Poisson's ratio. Uniaxial compression has been furthermore demonstrated to be a facile and efficient means for converting nf-DCC aerogels of broad, multiscale pore size distribution into entirely micro/mesoporous scaffolds of narrow size distribution at far-reaching preservation of porosity. Following this approach, thermally superinsulating nf-DCC aerogels (λ = 0.018 W m-1 K-1) have been prepared, whose intriguing mechanical properties, transparence, and nematic ordering bear great potential for other applications as well. [ABSTRACT FROM AUTHOR]