The Martini coarse-grained force field is one of the most popular coarse-grained models for molecular dynamics (MD) modelling in biology, chemistry, and material science. Recently, a new force field version, Martini 3, had been reported with improved interaction balance and many new bead types. Here, we present a new cellulose nanocrystal (CNC) model based on Martini 3. The calculated CNC structures, lattice parameters, and mechanical properties reproduce experimental measurements well and provide an improvement over previous CNC models. Then, surface modifications with COO− groups and interactions with Na+ ions were fitted based on the atomistic MD results to reproduce the interactions between surface-modified CNCs. Finally, the colloidal stability and dispersion properties were studied with varied NaCl concentrations and a good agreement with experimental results was found. Our work brings new progress toward CNC modelling to describe different surface modifications and colloidal solutions that were not available in previous coarse-grained models. Graphical abstract

Transparent wood (TW), a biocomposite material demonstrating optical transparency in the visible range, has attracted much interest in recent years due to great potential for ecofriendly applications, for instance, in construction industry and functionalized organic materials. Optical properties of TW, including transparency and haze, depend on a particular structure of cellulose‐based backbone compound, (mis‐)matching of the refractive indices (RIs) between TW compounds, and the polymer matrix. Although there are data of cellulose RIs for various forms of cellulose (fibers, powder, hot‐pressed films, etc.), these values might differ from an effective RI of the TW substrate. Herein, a numerical model of light propagation in the TW, based on the real cellular structure in wood, is presented and applied to estimate an effective RI of the delignified wood reinforcement in the experimentally investigated TW material. Ray‐tracing and rigorous electromagnetic approaches are compared for modeling light propagation in the TW. Ray tracing demonstrates considerably simplified yet accurate and efficient solutions. The work brings substantial progress toward realistic and practical wood modeling for the purpose of applications, materials design, and fundamental studies.

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