No abstract

No abstract

No abstract

We present a combined simulation and experimental study of the structure and dynamics of dilute, semidilute, and concentrated graphene oxide aqueous alkaline dispersions. These materials behave as lyotropic systems, with phase ordering as the concentration increases. The sheet spacing in the ordered phases is much broader than that expected by the classical Derjaguin–Landau–Verwey–Overbeek theory. Rheological responses in the isotropic phase are similar to rod-like liquid crystals (LCs), which follow the simplified Leslie–Ericksen (LE) model. The dispersions in the biphase and the discotic phase behave similarly to polydomain LC polymers, following the mesoscopic LE model [Larson–Doi (LD) model]. The LD model fits the time evolution of shear stress at startup flow, re-startup flow after the cessation of flow, and reversal flow in the discotic phase. Further, the Folgar–Tucker–Lipscomb model fits the stress overshoot in a startup flow, but not the reversal flow.

High-resolution 3D-printable hydrogels with high mechanical strength and biocompatibility are in great demand because of their potential applications in numerous fields. In this study, a material system comprising Pluronic F-127 dimethacrylate (FDMA) is developed to function as a direct ink writing (DIW) hydrogel for 3D printing. FDMA is a triblock copolymer that transforms into micelles at elevated temperatures. The transformation increases the viscosity of FDMA and preserves its structure during DIW 3D printing, whereupon the printed structure is solidified through photopolymerization. Because of this viscosity shift, various functionalities can be incorporated through the addition of other materials in the solution state. Acrylic acid is incorporated into the pregel solution to enhance the mechanical strength, because the carboxylate group of poly(acrylic acid) ionically crosslinks with Fe 3+ , increasing the toughness of the DIW hydrogel 37 times to 2.46 MJ m −3 . Tough conductive hydrogels are also 3D printed by homogenizing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate into the pregel solution. Furthermore, the FDMA platform developed herein uses DIW, which facilitates multicartridges 3D printing, and because all the materials included are biocompatible, the platform may be used to fabricate complex structures for biological applications.