Development of the Fibrillar and Microfibrillar Structure During Biomimetic Mineralization of Wood

Abstract

Wood is a hierarchical composite, consisting at its lowest hierarchy level of crystalline cellulose elementary fibrils with diameters of 2–4 nm embedded in a matrix of hemicelluloses and lignin. At the micrometer scale, it has a cellular architecture resembling a honeycomb structure. The transformation of the hierarchical wood structure into a silica replica has been reported recently. Its formation process and structural details are studied in this contribution. First, a silica/biopolymer composite is prepared by wood delignification and cell‐wall modification, followed by silica precursor infiltration and condensation. The calcination process is monitored to gain insight into the structure development upon decomposition of the biopolymers. The material changes its architecture gradually from fibrillar structures of 10–20 nm in diameter with homogeneous electron density, into fibrils of 8–10 nm in diameter with inhomogeneous electron density, exhibiting internal sub‐fibrillar structures of about 2 nm in diameter. The steps of the successful replication of the cellulose elementary fibrils into nanopores of similar diameter and orientation in a fibrillar silica matrix are demonstrated. These nanopore replicas of the original cellulose are wound in a steep helix within the macropore walls. These advanced materials may have lightweight structural applications and the nanopores may be advantageous for molecular separation.

Transparent plywood as a load-bearing and luminescent biocomposite

“…Note that the drying process and chemical treatment influence the observed pore structure [35,36]. This is in line with earlier work using two-dimensional smallangle X-ray scattering (SAXS) analysis [37,38]. After PMMA infiltration, ply stacking and polymerization, transparent plywood was obtained.…”

Modeling the Compressive Behavior of Anisotropic, Nanometer‐Scale Structured Silica

“…Hence, we have formulated a two‐level hierarchy, corresponding to the former wood cells and the main arrangement of the fibrous structures within the cell walls. The best‐fit value of our r should be seen in this light: While it is larger than the structural dimensions on the nanometer scale, as determined earlier, it reflects that larger structural features, observable in Figure a, contribute to an averaged effect.…”

Bio-inspired functional wood-based materials – hybrids and replicates

“…In situ small-angle X-ray scattering during calcination was used to follow the structure evolution of the infiltrated material in TEOS infiltrated wood. 141 This work clearly demonstrated that for delignified (and optionally functionalised) wood, the cellulose nanofibrils of only about 2–3 nm in diameter were transformed into pores of approximately the same diameter, thus confirming the replication of the lowest hierarchical level in wood. It was also shown that the TEOS monomer is capable of penetrating the cellulose fibrils via the swollen polyoses generating a polyose/silica matrix with embedded cellulose nanofibrils.…”