Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

作者：Camila Honorato‐Rios, Claudius Moritz Lehr, Christina Schütz, Roland Sanctuary, Михаил Анатольевич Осипов, Jörg Baller, Jan P. F. Lagerwall · 发表于：NPG Asia Materials · 年份：2018 · DOI：10.1038/s41427-018-0046-1 · 被引用次数：105 · 研究领域：Advanced Cellulose Research Studies、Polysaccharides and Plant Cell Walls

Colloids of electrically charged nanorods can spontaneously develop a fluid yet ordered liquid crystal phase, but this ordering competes with a tendency to form a gel of percolating rods. The threshold for ordering is reduced by increasing the rod aspect ratio, but the percolation threshold is also reduced with this change; hence, prediction of the outcome is nontrivial. Here, we show that by establishing the phase behavior of suspensions of cellulose nanocrystals (CNCs) fractionated according to length, an increased aspect ratio can strongly favor liquid crystallinity without necessarily influencing gelation. Gelation is instead triggered by increasing the counterion concentration until the CNCs lose colloidal stability, triggering linear aggregation, which promotes percolation regardless of the original rod aspect ratio. Our results shine new light on the competition between liquid crystal formation and gelation in nanoparticle suspensions and provide a path for enhanced control of CNC self-organization for applications in photonic crystal paper or advanced composites. The shape of nanoscale cellulose rods determines how they self-organize when suspended in water, show scientists in Luxembourg and the UK. Many interdependent factors determine whether the rods organize into a so-called liquid crystal state, dynamic and responsive, or if they are pinned in an immobile static gel. This makes it difficult to establish a clear understanding of the self-organization process. Jan ...