Preparation of porous regenerated cellulose microstructures via emulsion-coagulation technique

Cellulose-based materials, such as cellulose microspheres, have attracted enormous attention because of their widespread applications in water and protein purifications, chromatographic stationary phase, biocatalyst, drug delivery, electrode materials, etc. Here, homogenous and spherical porous regenerated cellulose microstructures (RCMSs) obtained from the agglomeration of micro/nanospheres were fabricated via a simple emulsion–coagulation–oven-drying process in pulp cellulose–tetraethylammonium hydroxide (TEAOH)/urea/H₂O solution, and the formation mechanism of the RCMSs was investigated by controlling the synthesis time. The results revealed that the uniform micro/nanospheres with a narrow size distribution of 600 nm–6 μm were first synthesized, followed by the formation of the RCMSs via the continuous agglomeration of the micro/nanospheres with the increasing synthesis time. Additionally, the RCMSs exhibiting micro/nanoscale pores with an adjustable mean diameter (r) of 280–103 μm were readily prepared by controlling the stirring speed between 300 and 1200 rpm. The re-wetted RCMSs exhibited a swelling ratio (SR) of 690–1400%, indicating their excellent swelling performance. Furthermore, the RCMSs with the structure of cellulose II exhibited good physical properties, including high porosity (P_r, 90–93%), pore volume (V_p, 7.0–10.3 cm³/g), specific surface area (S, 40–70 m²/g), and chemical/thermal stabilities. These findings can contribute to the design and exploitation of highly functional cellulose-based materials exhibiting micro/nanostructures.