Highly Anisotropic, Highly Transparent Wood Composites

Zhu, Mingwei; Song, Jianwei; Li, Tian; Gong, Amy; Wang, Yanbin; Dai, Jiaqi; Yao, Yonggang; Luo, Wei; Henderson, Doug; Hu, Liangbing

doi:10.1002/adma.201600427

Cited by 538 publications

(413 citation statements)

References 21 publications

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“…For an enhancement of the pore volume present in these structures chemical delignification processes adapted from pulp and paper industry are a promising approach. Rather recently, this concept was applied with subsequent delignification and functionalization for the development of transparent wood [15,16,17]. …”

Section: Introductionmentioning

confidence: 99%

Characterization of Wood Derived Hierarchical Cellulose Scaffolds for Multifunctional Applications

et al. 2018

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Functional materials of high porosity and hierarchical structure, based on renewable building blocks, are highly demanded for material applications. In this regard, substantial progress has been made by functionalizing micro- and nano-sized cellulose followed by its reassembly via bottom-up approaches. However, bottom-up assembly processes are still limited in terms of upscaling and the utilization of these building blocks presupposes the disassembly of the plant feedstock inherit hierarchical cellulose scaffold. To maintain the three-dimensional structure, delignification processes from pulp and paper production were recently adapted for the treatment of bulk wood. Yet, a detailed chemical analysis and the determination of macroscopic swelling/shrinkage parameters for the scaffolds, necessary for a systematic design of cellulose scaffold based materials, are still missing. Here, acidic bleaching and soda pulping were used for producing cellulose scaffolds, for functional materials under retention of their inherent hierarchical structure. Spatially resolved chemical investigations on thin sections by Raman microscopy provided detailed information on the induced alterations at the cell wall level, revealing significant differences in dependence of the chemistry of the pre-treatment. An adaption to bulk wood samples proved the applicability of these treatments at larger scales and volumetric alterations at different atmospheric conditions indicated the effect of the altered porosity of the scaffolds on their hygroscopic behaviour.

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Section: Introductionmentioning

confidence: 99%

Characterization of Wood Derived Hierarchical Cellulose Scaffolds for Multifunctional Applications

et al. 2018

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“…However, there always exists minor refractive index mismatch between the wood components and infiltrated polymer that leads to the light scattering. [11,17] While transmittance describes optical losses of a material, i.e., the fraction of the optical energy flux passing Transparent wood (TW) is a biocomposite material with hierarchical structure, which exhibits high optical transmittance and anisotropic light scattering. This leads to formation of structural air-filled voids in the walls of the cellulose fibers consisting of nanofibrils (Figure 1c).…”

mentioning

confidence: 99%

“…[11,17] While transmittance describes optical losses of a material, i.e., the fraction of the optical energy flux passing Transparent wood (TW) is a biocomposite material with hierarchical structure, which exhibits high optical transmittance and anisotropic light scattering. [11,17] While transmittance describes optical losses of a material, i.e., the fraction of the optical energy flux passing Transparent wood (TW) is a biocomposite material with hierarchical structure, which exhibits high optical transmittance and anisotropic light scattering.…”

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confidence: 99%

Light Scattering by Structurally Anisotropic Media: A Benchmark with Transparent Wood

Vasileva

Chen

et al. 2018

Advanced Optical Materials

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perpendicularly to the cellulose fibers, and 1.596 along with the fibers), hemicellulose (1.532), and lignin (1.61). [3] While holocellulose (cellulose and hemicellulose) is optically colorless, lignin is the main source of absorption (about 80-95% of wood light absorption) in the visible range. [10] Thus, lignin removing [11] or deactivating the chromophores inside lignin is required to make wood transparent. [12] Although major part of lignin is removed during chemical modification, some residual amount (1-3%) still remains in the wood [11] introducing minor absorption. A delignified wood (Figure 1a) is not yet transparent due to strong scattering of light, which occurs on the interfaces between the material structural components and air-filled voids between/within them. To minimize such scattering, the delignified template is infiltrated with a polymer of refractive index approximately matching the wood compounds. In several previous studies, polymerized methyl methacrylate (PMMA) whose refractive index is close to the average refractive index of delignified wood template (≈1.53) [11] was implemented. However, there always exists minor refractive index mismatch between the wood components and infiltrated polymer that leads to the light scattering. Moreover, as a consequence of mesoporous hierarchical structure of a wood template [13] with feature sizes scaling from micrometers-cellulose fibers, vessels, rays [14] (schematically presented in Figure 1b) down to nanometers (nanofibrils), [1,15] polymer infiltration process is not perfect, e.g., due to surface compatibility issues. This leads to formation of structural air-filled voids in the walls of the cellulose fibers consisting of nanofibrils (Figure 1c). It should be noted that additional airfilled voids can also be created via polymer shrinkage during polymerization [16] (Figure 1c). Hence, scattering in TW is caused by several factors: minor mismatch of the refractive indices between the delignified wood template and infiltrated polymer, multiscale porous hierarchical structure of the wood consisting of macro-, meso-, and nanopores, and presence of air-filled voids. Thus, despite relatively high optical transmittance, TW is, in fact, an optically anisotropic scattering medium.Traditionally optical properties of TW have been characterized via measuring the light total hemispherical luminous transmittance (referred as transmittance in the literature about TW) and haze. [11,17] While transmittance describes optical losses of a material, i.e., the fraction of the optical energy flux passing Transparent wood (TW) is a biocomposite material with hierarchical structure, which exhibits high optical transmittance and anisotropic light scattering. Here, the relation between anisotropic scattering and the internal structure of transparent wood is experimentally studied and the dependence of scattering anisotropy on material thickness, which characterizes the fraction of ballistic photons in the propagating light, is shown. The limitations of the conventional haze, as...

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“…Highly transparent wood composite, taking advantage of the unique microstructure in wood, also has been obtained and could be used as structural materials in automobiles and optoelectronics in the future1. In addition, cellulose, hemicelluloses and lignin, the three major constituent biopolymers of wood, are widely used in other applications (Supplementary Fig.…”

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confidence: 99%

Partial delignification of wood and membrane preparation using a quaternary ammonium ionic liquid

Miao

Jiang

et al. 2017

Sci Rep

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This work determined that southern yellow pine wood can almost be completely dissolved in the quaternary ammonium ionic liquid tetrabutylammonium acetate with dimethyl sulfoxide (in a 2:8 mass ratio), after minimal grinding, upon heating at 85 °C for three dissolution/reconstitution cycles, each 1.5 h. Approximately 34.6% of the native lignin and 67.4% of the native carbohydrates present in the original wood can subsequently be extracted, respectively, and were assessed. A gradual decrease in lignin with increased extraction cycles resulted in increased crystallinity index of the cellulose II in the cellulose-rich residue, as confirmed by X-ray diffraction. An increasingly homogeneous macrostructure in the cellulose-rich residue was also evident from scanning electron microscopy images. Membranes cast directly from either wood or cellulose-rich residue solutions in the same tetrabutylammonium acetate/dimethyl sulfoxide system, were prepared using a papermaking-like process. Morphological and mechanical studies indicated that lignin extraction made the membranes more uniform and flexible. Systematic increases in the fibril lengths and orientations of the recovered materials were also found with decreasing lignin contents on the basis of atomic force microscopy analysis. This work demonstrates that relatively efficient partial separation of pine wood and subsequent membrane preparation are possible using a quaternary ammonium ionic liquid.

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Highly Anisotropic, Highly Transparent Wood Composites

Cited by 538 publications

References 21 publications

Characterization of Wood Derived Hierarchical Cellulose Scaffolds for Multifunctional Applications

Characterization of Wood Derived Hierarchical Cellulose Scaffolds for Multifunctional Applications

Light Scattering by Structurally Anisotropic Media: A Benchmark with Transparent Wood

Partial delignification of wood and membrane preparation using a quaternary ammonium ionic liquid

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