Progress on Cellulose Esterification – Control Over Surface to Bulk Modification

The industrial acetylation of high-purity technical cellulosics is well studied mechanistically and known to involve elementary fibril chain exfoliation, leading to cellulose triacetate (CTA) for-mation Sassi, & Chanzy, 1995). The biodegradability of such materials, in the context of the single-use plastics di-rective, are justifiably under scrutiny, which is very much related to the increased hydrophobicity of high DS cellulose acetates (Yadav, & Hakkarainen, 2021).

Recently we developed two methods that allow for fine control over the regioselectivity of sur-face acetylation of different cellulose substrates (Koso et al., 2022, Beaumont et al., 2021). One method involves the controlled sur-face modification of dried cellulose substrates, e.g. nanocelluloses, pulps & regenerated fibres (Koso et al., 2022). Another, takes advantage of the novel properties of surfacebound water and mechanical ac-tivation to yield a thorough penetration of the fibre network, yet, still maintaining high regiose-lectivity (confinement of reaction to fibril surfaces). These methods are especially illustrated through the combined application of a novel solution-state NMR method, high resolution AFM and WAXS. The regioselectivity results are also supported by DFT-based transition-state model-ling on a cellulose surface fragment.