Natural fiber welding (NFW) typically uses an ionic liquid such as 1-ethyl-3-methylimidazolium acetate (EMImAc) to partially dissolve cellulose and weld strands of cotton thread into an amorphous network. Removal of EMImAc through successive solvent rinses and drying produces all-cellulose structures ranging from non-porous biocomposites to highly porous xerogels based on the identity of the solvent exchange. However, how and why certain solvent interactions actually deliver mesoporous fiber-welded biopolymer materials with controlled porosity is poorly understood. In this study, we demonstrate that the porosity of a welded cotton xerogel can be controlled by tuning the solvent exchange and drying steps. NFW cotton thread is rinsed of EMImAc by solvent exchange with one or a series of solvents of varying polarities. We determine that the polarity of the final solvent in the series can control the BET surface area of the dry product, with nonpolar solvents creating xerogels. This porosity can be further enhanced using lyophilization, a less disruptive evaporation technique, to deliver a maximum BET surface area of 232 m(2) g(-1) when cyclohexane is used as the final rinse solvent.
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