The structural features of wood were replicated in silica on all levels of hierarchy from the macroscopic to the nanoscopic level of the cellulose elementary fibrils. This was achieved by a series of processing steps on spruce wood templates. Sodium chlorite was used to partially remove the lignin matrix from the wood cell walls, exposing the cellulose fibrils. These were optionally functionalized with maleic acid anhydride to stabilize the fibrillar structure and reduce the shrinkage of the template. Repeated infiltration with tetraethyl orthosilicate in ethanol deposited silica on the fibrils. Calcination at 500°C removed the rest of the organic template by oxidation and resulted in the fusion of the deposited material into a positive silica replica. Small-angle x-ray scattering evidenced fibrillar structures parallel to the original cellulose fibrils at length scales in the order of 10 nm, suggesting the successful nanoscopic replication of the cellulose fibrils and their orientation.

In order to provide parameters that can be used to tailor the crystalline and supramolecular structures of pure polyhydroxybutyrate, we synthesized polymers with fractions of meso groups in the range 0.5−1. We confirmed the random polymerization of R and S enantiomers by the catalyst. From Xray diffractograms, the lattice parameters were determined; they remained constant for the observed range of fractions. We also traced the directional crystallite sizes over tacticity, which change significantly for one unit cell direction. The respective crystalline phase atom fractions were quantified by iteratively fitting amorphous phase diffraction patterns. We found that the crystalline contents of small-crystallite polyhydroxybutyrates have so far been underestimated. X-ray diffraction and transmission electron microscopical observations from polymers with meso group fractions of 0.5 are discussed. To facilitate the quantification of crystalline atom fractions, we refined two accessible infrared absorption spectroscopy-based indices. These indices, and the fundamental correlations between chemical and crystallite structuring reported herein, allow to tune structure-dependent properties, e.g., melting point and toughness, of mixedtacticity polyhydroxybutyrates over wide ranges.

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.