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Nanostructured Cellulose II Gel Consisting of Spherical Particles

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journal contribution
posted on 16.06.2016 by Marco Beaumont, Harald Rennhofer, Martina Opietnik, Helga C. Lichtenegger, Antje Potthast, Thomas Rosenau
Cellulose nanofibrils (CNF) are usually obtained by breaking down the lignocellulosic structure of pulp, i.e., as cellulose I allomorph and according to rather energy-intensive pathways. In contrast to those approaches, TENCEL gel is obtained from a nonfibrous cellulose II precursor directly out of the Lyocell process in a deceptively energy-efficient way: After enzymatic treatment and only one cycle in a high-pressure homogenizer (comparing to up to 20 cycles for CNF manufacture) the final gel is obtained. The utilization of a starting material from an already existing industrial process is another distinct advantage. This novel cellulose II gel possesses a particle-like, homogeneous morphology and is composed of individual particles with a size of less than one micron, featuring the rheological behavior of a soft solid. The course of the gel production process was studied with respect to changes in crystallinity, appearance and molecular weight, whereas the morphology and size of the final gel particles were assessed comprehensively by light-microscopy, dynamic light scattering and electron microscopy. In water, the individual particles form aggregates with a mean size of 11 μm. The viscoelastic gel forms highly porous cryogels with a surface area of 298 m2/g and a well-defined nanostructure. These features were studied in depth by SAXS, nitrogen sorption experiments and SEM. The economic production in combination with the highly accessible surface offers unique properties, and applications are envisioned as tailored, high performance materials.