Liquid crystalline (LC) phase transition and gel-sol transition in the solutions of microcrystalline cellulose (MCC) and ionic liquid (1-ethyl-3-methylimidazolium acetate, EMIMAc) have been investigated through a combination of polarized optical microscope (POM) observation and rheological measurements. Molecular LC phase forms at the 10 wt % cellulose concentration, as observed by POM, whereas the critical gel point is 12.5 wt % by rheological measurements according to the Winter and Chambon theory, for which the loss tangent, tan δ, shows frequency independence. Dramatic decreases of G' and G'' in the phase transition temperature range during temperature sweep are observed due to disassembling of the LC domain junctions. The phase diagram describing the LC phase and gel-sol transitions is obtained and the associated mechanisms are elucidated. A significant feature shown in the phase diagram is the presence of a narrow lyotropic LC solution region, which potentially has a great importance for the cellulose fiber wet spinning.

Stretchable ionogels have recently emerged as promising soft and safe ionic conductive materials for use in wearable and stretchable electrochemical devices. However, the complex preparation process and insufficient thermomechanical stability greatly limit the precise rapid fabrication and application of stretchable ionogels. Here, we report an in situ 3D printing method for fabricating high-performance single network chemical ionogels as advanced strain sensors. The ionogels consist of a special cross-linking network constructed by poly­(ionic liquid) and hyperbranched polymer (macro-cross-linkers) that exhibits high stretchability (>1000%), superior room-temperature ionic conductivity (up to 5.8 mS/cm), and excellent thermomechanical stability (−75 to 250 °C). The strain sensors based on ionogels have a low response time (200 ms), high sensitivity with temperature independence, long-term durability (2000 cycles), and excellent temperature tolerance (−60 to 250 °C) and can be used as human motion sensors. This work provides a new strategy to design highly stretchable and superior stable electronic devices.

The liquid crystalline phase behavior and sol-gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol-gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects.