Computational description of the gelation in cellulose aerogels

Abstract

Biopolymer-based aerogels are a promising biodegradable alternative to standard porous materials for various applications, such as thermal insulation or adsorption. With rapidly increasing demand for advanced materials that meet demands of the sustainable development, cellulose aerogels are attracting a considerable attention. Their microstructure exhibits high porosity, excellent sorption capacity and very well-developed surface area. The fundamental understanding of the system is an essential step towards a digital twin and rapid material development. Thus, there is a need for a comprehensive numerical approach that would provide an insight into the synthesis process. Discrete element method (DEM)-based model of the cellulose gelation was developed using MUSEN as a framework. The diffusion of cellulose chains is represented with a coarse-grained Langevin dynamics. The functional model describes the degrees of freedom of the D-glucose molecules connected with glycosidic bonds. Van der Waals interaction between the molecules is described with the non-bonding Lennard-Jones potential. A computationally obtained gel is post-treated with washing and solvent exchange. Subsequently, the solvent is extracted from the pore network of the gel by the supercritical drying. The parameters sensitivity analysis results provide an understanding of the influence of the polymer-polymer interaction strength on the gelation kinetics and gel porosity. The pore size distribution is analysed after each step of the synthesis: gelation, washing, solvent exchange and drying, explaining the influence of the solvent on the gel structure properties. The model was validated with experimental data and it indicates a high potential for prediction of cellulose aerogels’ properties with high accuracy. The proposed approach is a significant step towards creation of a digital twin for cellulose aerogels, but also has a great potential to be extended for systems based on other polymers.