Abstract Understanding the properties of hierarchical materials such as wood requires combining information representing different length scales. Scanning wide-angle X-ray scattering (WAXS) connects the nanoscale cell wall structure to the scale of the annual growth rings, as demonstrated here by studying radially cut slices of mature softwood (Scots pine and Norway spruce), including the bark. WAXS offers information on the crystalline structure and other properties of the semi-crystalline cellulose microfibrils in the plant cell walls. Scanning-WAXS is data intensive but applicable to even laboratory X-ray sources, making it relatively accessible but underutilized. We present ways of efficiently analyzing the large data sets by robust analysis methods, principal component analysis (PCA) and clustering. We use PCA directly with two-dimensional scattering patterns, making the method highly applicable and easy to use. Scanning over wood samples containing xylem and bark, several different tissues were studied, such as xylem, phloem and outer bark, and scattering patterns for all these tissues are presented and compared. In our experiments, X-ray microtomography information was also used to verify and visualize the observations from the scattering data analysis. In the spruce xylem, the intra-annual variation of mean microfibril angle and crystallinity index was linear with respect to radial distance, whereas the density showed a steeper increase with radial distance, better modeled with a second order function. Scanning wide-angle X-ray scattering was shown to be able to connect different length scales and thus be able provide new information on the multi-scale structure of wood.

Abstract Softwood kraft pulp is known to produce one of the strongest papers, with main application areas in tissues, packaging, and high-quality or specialty papers. These tailored applications often crave chemical modification of the fibers to optimize and tailor their inherent properties. This paper presents two scalable methodologies, gas phase reactions and kneading reactions, for the esterification of bleached kraft pulp (BKP) with itaconic anhydride (ITA). Itaconic anhydride is bioderived with a structure similar to succinic or maleic anhydride, two commonly used chemicals for modifying pulps to introduce charge groups on the cellulose fibers. Although similar in structure, itaconic derivatives also contain an exocyclic, out-of-chain unsaturation, which is useful for additional chemical modifications, such as Michael additions and polymerization reactions. The modification of BKP was performed on never-dried and water-free pulp, aiming to produce highly charged fibers while preserving the overall fiber structure and thereby their intrinsic properties. The reaction yields were investigated by varying molar ratio, temperature, and reaction time, and the modified fibers were characterized using ATR-FTIR, solid state CP/MAS 13 C-NMR, XRD, titration techniques, and water retention values. The different modification methods showed differences in the spatial distribution of the substituents, preferably modifying the fiber surface or the fiber wall interior. In general terms, modifications facilitated through kneading showed a higher degree of modification of the fiber wall interior, whilst gas-phase mediated reactions preferentially modified the fiber surface. This allows for tailoring the location of the modification, decorating the fibers within or on the surface, and opening routes for a customizable pulp.