Concentrated cellulose nanocrystals (CNC) suspensions are known to self-assemble into liquid crystalline cholesteric phase. However, the origin of this chirality transfer is still matter of discussion. In this work, we used a tailor-made biopolymer, xyloglucan (XG), at a very small molar mass (20,000 g/mol) that adsorb at on the cellulose surface. We showed that the addition to a dispersion of CNC at 60 g/L of XG up to 10 g/L decreased the anisotropic volume fraction, increased the cholesteric pitch, and kept constant the inter-CNC distance implying a change in the twist angle and a lower chiral strength. These results indicate that a very limited modi cation of CNC in surface can induce important variation of the cholesteric order. Above 10 g/L XG, XG-covered CNCs decreased the cholesteric pitch and preferentially concentrated in the isotropic phase, decreasing the global cholesteric liquid crystal (CLC) order.
Hydrogels were prepared at high solid contents (70−100 g/L) with cellulose nanocrystals (CNC) and very short xyloglucans (XGs). At 70 g/L, CNCs form cholesteric liquid crystals regularly spaced by a distance of 30 nm. This structure was preserved after adsorption of XG with a molar mass (M w ) of 20,000 g/mol (XG20) but was lost at 40,000 g/mol (XG40). Rheological measurements discriminated domains where an increasing M w from XG20 to XG40 gave rise to drastic changes in storage moduli (on 3 orders of magnitude). At 40,000 g/mol, transient systems were obtained and a re-entrant glass−gel−glass transition was observed with increasing XG concentrations. This was interpreted in terms of the length and stiffness of the chain in relation to the inter-CNC distance. Liquid-to-glass-to-gel transitions were attributed to an XG adsorption type according to train or trail conformations or interconnected structures. Such tunable properties may further have implications on the in vivo role of XG during cell wall extension.
Concentrated cellulose nanocrystals (CNC) suspensions are known to self-assemble into liquid crystalline cholesteric phase. However, the origin of this chirality transfer is still matter of discussion. In this work, we used a tailor-made biopolymer, xyloglucan (XG), at a very small molar mass (20,000 g/mol) that adsorb flat on the cellulose surface. We showed that the addition to a dispersion of CNC at 60 g/L of XG up to 10 g/L decreased the anisotropic volume fraction, increased the cholesteric pitch, and kept constant the inter-CNC distance implying a change in the twist angle and a lower chiral strength. These results indicate that a very limited modification of CNC in surface can induce important variation of the cholesteric order. Above 10 g/L XG, XG-covered CNCs decreased the cholesteric pitch and preferentially concentrated in the isotropic phase, decreasing the global cholesteric liquid crystal (CLC) order.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.