Liquid crystalline and rheological properties of chitin whiskers with different chemical structures and chargeability

The liquid crystalline and rheological properties of chitin whiskers (CHWs) are significant for their application in fabrication of highly ordered composite materials and optical components. The aim of this work was to elucidate the influence of chemical structure and chargeability (zeta potential, electropositivity, electronegativity or zwitterionic character) on the liquid crystalline and rheological properties of CHWs. Firstly, CHWs with different chemical structure, including positively charged whiskers (CHWs and CHWs-D/60 min) and negatively charged whiskers (mCHWs), were designed via acid hydrolysis, deacetylation, and maleation, respectively. Subsequently, the chargeability of the above whiskers was further regulated by protonation or deprotonation. The whisker aqueous suspensions with high zeta potential behaved as nematic liquid crystals or chiral nematic liquid crystals, whereas those with low zeta potential had no liquid crystal characteristics. The viscosity, G', and G" values of the CHWs and CHWs-D/60 min aqueous suspensions treated with protonation were lower than those of the corresponding whiskers treated with deprotonation. However, the mCHWs exhibited different changes in their rheological properties under protonation or deprotonation due to the electronegativity and zwitterionic characteristics. In addition, the effects of ionic strength and pH on the liquid crystalline and rheological properties of CHWs, CHWs-D/60 min, and mCHWs aqueous suspensions varied since the chemical structure and chargeability of whiskers differ.