MAIN CONCLUSION : [EtPy][Br] is more reactive toward lignin than toward the PSs in wood cell walls, and [EtPy][Br] treatment results in inhomogenous changes to the cell wall's ultrastructural and chemical components. The effects of the ionic liquid 1-ethylpyridinium bromide ([EtPy][Br]), which prefers to react with lignin rather than cellulose on the wood cell walls of Japanese cedar (Cryptomeria japonica), were investigated from a morphology and topochemistry point of view. The [EtPy][Br] treatment induced cell wall swelling, the elimination of warts, and the formation of countless pores in the tracheids. However, many of the pit membranes and the cellulose crystalline structure remained unchanged. Raman microscopic analyses revealed that chemical changes in the cell walls were different for different layers and that the lignin in the compound middle lamella and the cell corner resists interaction with [EtPy][Br]. Additionally, the interaction of [EtPy][Br] with the wood cell wall is different to that of other types of ionic liquid.

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Japanese cedar (Cryptomeria japonica) was treated with the ionic liquid (IL) 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which is a solvent for cellulose, and the changes in the chemical components and their distribution in wood cell walls have been investigated by Raman microscopy. Raman spectra, recorded from various areas of the cell walls, showed that lignin in the compound middle lamellae (CML) and cell corners (CC) was resistant to the reaction with [C2mim][Cl], but its molecular structure changed partially. The reactivity of cellulose and hemicelluloses with [C2mim][Cl] was higher than that of lignin in the cell wall, and the cell wall structure was maintained even in an advanced state of the reactions. The effects of [C2mim]-[Cl] on cellulose and hemicelluloses in the cell wall were homogeneous, whereas that of lignin was inhomogeneous.