Tiinamari Seppänen, Kristoffer Meinander, Monika Österberg, Emily D. Cranston, Tekla Tammelin
Abstract: Porous cellulose and nanocellulose materials, such as foams and aerogels, are widely used in numerous applications due to their large surface area, sorption capacity, mechanical resilience, and overall versatility. Additionally, porous cellulose materials provide extensive interaction sites that can facilitate a variety of chemical processes. Herein, ultrathin nanocellulose model surfaces with a 2D open-pore structure are presented that mimic the complexity of porous cellulose fiber materials. A sacrificial templating approach is used by spin coating a mixture of 2,2,6,6-tetramethylpiperidin-1-oxyl-oxidized cellulose nanofibrils (TOCNFs) and polystyrene (PS) nanoparticles onto a silicon wafer, followed by selective nanoparticle dissolution. Scanning electron microscopy and atomic force microscopy reveal an ultrathin TOCNF layer with hierarchical morphology and spherical open pores (70 nm diameter), with a root mean square roughness of 19 nm. The surface coverage of nanoparticles is controlled primarily by changing the TOCNF concentration, and to a lesser extent, the ratio between PS nanoparticles and TOCNFs. X-ray photoelectron spectroscopy supports the complete removal of the PS template, leaving behind a pure TOCNFs layer. Open-pore structured nanocellulose model surfaces provide a tool to investigate interfacial phenomena in porous materials constructed from fibers and/or nanocelluloses, thus advancing the engineering of functional porous cellulose-based materials.
