We report a novel electrorheological suspension based on twodimensional polyaniline decorated graphene sheets, which exhibits enhanced electrorheological effect compared to the traditional granular polyaniline suspension under electric fields.It is very interesting to control the viscosity or viscoelasticity of materials by external electric or magnetic stimuli because of their potential use in various devices in mechanical, biomedical and robotic fields. 1 An electrorheological (ER) suspension consisting of polarizable particles dispersed in a non-conducting liquid is considered to be one of the most important smart materials with electrically tunable viscosity and viscoelasticity. 1,2 This tunable rheological characteristic originates from the ordered self-assembly of the particulate phase in the ER suspension under an applied external electric field. Although the property of the ER suspension is similar to that of a magnetorheological (MR) suspension under an applied magnetic field, 3 the present ER suspensions do not possess versatile performance and problems such as low yield stress, large current density, particle sedimentation, and thermal instability still require a more effective solution.Recently, using nanoparticles as the dispersal phase or filler has attracted considerable interest in the development of a non-conventional ER suspension. 1b,4 In particular, significant attention has been paid to one-dimensional (1D) nanofiber suspensions because it was found that the nanofiber suspensions exhibited not only higher ER or MR effect, but also reduced particle sedimentation compared to the conventional granular suspensions. 5,6 Property enhancements originated from the nature of nanofibers, e.g., small size, large aspect ratio, and anisotropic electronic or magnetic properties. Besides 1D nanomaterials, two-dimensional (2D) ones also attracted much interest due to their unique properties and promising applications. 7 Graphene-based material is one of the most popular 2D nanomaterials and it has many advantages, such as low manufacturing cost, facile mass production, enhanced physical behavior, and so on. 8 Unfortunately, pure graphene is not suitable for ER application because of its high conductivity. Very recently, a kind of chitosan/ graphene nanocomposite was prepared and was observed to form a chain-like structure under electric fields by an optical microscope. 9 In contrast to graphene, graphene oxide (GO) is appropriate for ER application because of the reduced conductivity. Zhang et al. firstly used GO in ER suspensions by forming a GO/polymer composite and GO absorbed polymer microspheres. 10 But these GO-based ER materials were still micro-sized stacking particles and their ER effect also needed to improve for practical applications.On the other hand, polyaniline (PANI) is one of the most important ER materials because of its anhydrous characteristic, simple preparation, low cost, good thermal stability, and controllable conductivity. 2a Various PANI with modifications or as part of composites h...

Two partially gelled (crosslinked) layers of elastomer were pressed into intimate contact and the gelation reaction was then taken to completion. By varying the extent of initial gelation, the degree of chemical interlinking was varied from zero, when two fully reacted sheets were pressed together, up to a level characteristic of the final density of molecular linking within each layer, when they were brought together before any reaction had occurred. The strength of adhesion between the layers was measured under threshold conditions, i.e., at low rates of peel, at high temperatures, and, in some instances, with the layers swollen with a compatible liquid. Linear relations were obtained between the threshold work of detachment per unit of interfacial area and the amount of chemical interlinking, deduced from the kinetics of molecular linking within each layer. At any degree of interlinking, ranging from zero to the fully interlinked state, the work of detachment was lower for networks composed of shorter molecular chains, in accordance with the Lake–Thomas theory for the threshold strength of elastomer networks. By extrapolation to the fully interlinked state, the strength of adhesion corresponding to cohesive rupture was inferred. These values agreed with measured tear strength for polybutadiene gelled by a free‐radical process. For a sulfur crosslinking system, and for both free‐radical and sulfur crosslinking of poly(ethylene‐co‐propylene), the threshold tear strength of the elastomer was found to be much higher than the extrapolated value from adhesion measurements. This discrepancy is ascribed to roughness of the tear plane in relatively strong elastomers, in contrast to the smooth separation of flat adhering layers. Adhesion of fully crosslinked sheets was generally low, 1–2 J/m2. Higher values, 5–25 J/m2, were found with sulfur crosslinking systems, especially those yielding a high proportion of polysulfidic crosslinks. Interlinking via polysulfide crosslink interchange reactions is suggested in these cases.

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We report a new electrorheological fluid based on mesoporous silicacoated graphene nanosheets. Coating with mesoporous silica limits the high conductivity of graphene and improves the dispersed ability of nanosheets in silicone oil, while the graphene core helps to induce large and fast particle polarization for high electrorheological response, in particular under AC electric fields.