Crystalline nanoxylan from hot water extracted wood xylan at multi-length scale : Molecular assembly from nanocluster hydrocolloids to submicron spheroids

: Zhang Yidong, Wang Luyao, Zhang Hao, Rosqvist Emil, Lastusaari Mika, Peltonen Jouko, Vähäsalo Lari, Xu Chunlin, Wang Xiaoju, Pranovich Andrey

Publisher: Elsevier

: 2024

: Carbohydrate Polymers

: 122089

: 335

: 0144-8617

: 1879-1344

DOI: https://doi.org/10.1016/j.carbpol.2024.122089(external)

: https://www.sciencedirect.com/science/article/pii/S0144861724003151(external)

: https://research.utu.fi/converis/portal/detail/Publication/387505975(external)

As a contribution to expand accessibility in the territory of bio-based nanomaterials, we demonstrate a novel material strategy to convert amorphous xylan preserved in wood biomass to hierarchical assemblies of crystalline nanoxylan on a multi-length scale. By reducing the end group in pressurized hot water extracted (PHWE) xylan to primary alcohol as a xylitol form with borohydride reduction, the endwise-peeling depolymerization is effectively impeded in the alkali-catalyzed hydrolytic cleavage of side substitutions in xylan. Nanoprecipitation by a gradual pH decrease resulted in a stable hydrocolloid dispersion in the form of worm-like nanoclusters assembled with primary crystallites, owing to the self-assembly of debranched xylan driven by strong intra- and inter-chain H-bonds. With evaporation-induced self-assembly, we can further construct the hydrocolloids as dry submicron spheroids of crystalline nanoxylan (CNX) with a high average elastic modulus of 47–83 GPa. Taking the advantage that the chain length and homogeneity of PHWE-xylan can be tailored, a structure-performance correlation was established between the structural order in CNX and the phosphorescent emission of this crystalline biopolymer. Rigid clusterization and high crystallinity that are constructed by strong intra- and inter-molecule interactions within the nanoxylan effectively restrict the molecular motion, thereby promoting the emission of ultralong organic phosphorescence.

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