Water-accessibility of interfibrillar spaces in spruce wood cell walls

Abstract

Water interactions and accessibility of the nanoscale components of plant cell walls influence their properties and processability in relation to many applications. We investigated the water-accessibility of nanoscale pores within the fibrillar structures of unmodified Norway spruce cell walls by small-angle neutron scattering (SANS) and Fourier-transform infra-red (FTIR) spectroscopy. The different sensitivity of SANS to hydrogenated ($$\hbox {H}_2\hbox {O}$$ H 2 O ) and deuterated water ($$\hbox {D}_2\hbox {O}$$ D 2 O ) was utilized to follow the exchange kinetics of water among cellulose microfibrils. FTIR spectroscopy was used to study the time-dependent re-exchange of OD groups to OH in wood samples transferred from liquid $$\hbox {D}_2\hbox {O}$$ D 2 O to $$\hbox {H}_2\hbox {O}$$ H 2 O . In addition, the effects of drying on the nanoscale structure and its water-accessibility were addressed by comparing SANS results and the kinetics of water exchange between never-dried and dried/rewetted wood samples. The results of the kinetic analyses allowed to identify two processes with different timescales. The diffusion-driven exchange of water in the spaces between microfibrils, which was observed with both SANS and FTIR, takes place within minutes and rather homogeneously. The second, slower process appeared only in the OD/OH re-exchange followed by FTIR, and it still continued after several weeks of immersion in $$\hbox {H}_2\hbox {O}$$ H 2 O . SANS could not detect any significant difference between the never-dried and dried/rewetted samples, whereas FTIR revealed a small portion of OD groups that resisted the re-exchange and this portion became larger with drying. Graphic abstract

An Oxidative Enzyme Boosting Mechanical and Optical Performance of Densified Wood Films

“…The d c value obtained for the D‐wood veneer corresponded well with previous results obtained from delignified birch (3 nm) [ 25 ] and native spruce wood (3.9 nm). [ 26 ] Thus, there was no significant change in the wood microstructure in terms of the organization of cellulose microfibrils in the D‐wood veneer as compared to native wood. Interestingly, the increased d c value obtained after LPMO oxidation revealed a profound change in the organization of cellulose microfibrils in the wood cell wall.…”

Combined analysis of microstructures within an annual ring of Douglas fir (Pseudotsuga menziesii) by dynamic mechanical analysis and small angle X-ray scattering

“…Small angle scattering is one of the structural analyses methods gaining popularity in the field of wood science. For example, Penttilä et al have studied the relationship between moisture content changes and microstructures changes in wood using X-ray and neutron scattering [13,14,26]. In these experiments, in situ measurement plays an important role, which is one of the advantages of small-angle scattering.…”

Nanoscale Mechanism of Moisture-Induced Swelling in Wood Microfibril Bundles

“…(a) Results of SAXS fits using the WoodSAS model (SI eq S3) (see Figure S13 for all results). (b) Microfibril packing distance as a function of MC (0.7 × MC c ) as determined from the periodic bundle model (see Figure S15 for non-periodic model) and a comparison to experimental SAXS and SANS results ,,,,, (MC of 41% used for Norway spruce in water-saturated state; error bars correspond to standard deviation between samples). Snapshots of the periodic model with density of water in blue are shown on the right.…”

“…Other works have reported abrupt changes in the mechanical properties of wood, its susceptibility to fungal degradation, and water diffusion and hydrogen bonding at 22 (see Figure S13 for all results). (b) Microfibril packing distance as a function of MC (0.7 × MC c ) as determined from the periodic bundle model (see Figure S15 for non-periodic model) and a comparison to experimental SAXS and SANS results 20,22,23,29,58,59 (MC of 41% used for Norway spruce in water-saturated state; 39 similar MCs, 60−62 which coincides with the softening of hemicelluloses. 3 A previous diffraction study also found the largest moisture-related changes in the lattice parameters of spruce wood cellulose below MC 13%.…”