A facile and general method to covalently functionalize graphene oxide (GO) with copolymers, using poly(styrene-co-methylmethacrylate) (P(St-co-MMA)) as an example, via miniemulsion polymerization is described in this study. After in situ reduction, insulating GO is converted to conductive reduced-graphene oxide (RGO). P(St-co-MMA) grafted RGO as conducting filler was incorporated into immiscible polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend to prepare conductive polymer composites (CPCs). The lowest percolation threshold (0.02 vol%) among all the reported values for graphene-filled CPCs was achieved due to the controllable preferential distribution of the modified RGO at the interfacial region between PS and PMMA phases, attributed to P(St-co-MMA) grafted on the surface of RGO behaving as compatibilizers to improve interfacial interactions with both the two phases. Moreover, P(St-co-MMA) grafting modified RGO could obviously enhance the compatibility reflected by a significant reduction of the size of dispersed phase, for an example, by nearly one order of magnitude for PS/PMMA (4/1 in volume) blends.

Some precision electronics such as signal transmitters need to not only emit effective signal but also be protected from the external electromagnetic (EM) waves. Thus, directional electromagnetic interference (EMI) shielding materials (i.e., when the EM wave is incident from different sides of the sample, the EMI shielding effectiveness (SE) is rather different) are strongly required; unfortunately, no comprehensive literature report is available on this research field. Herein, Ni-coated melamine foams (Ni@MF) were obtained by a facile electroless plating process, and multiwalled carbon nanotube (CNT) papers were prepared via a simple vacuum-assisted self-assembly approach. Then, step-wise asymmetric poly(butylene adipate-co-terephthalate) (PBAT) composites consisting of loose Ni@MF layer and compact CNT layer were successfully fabricated via a facile solution encapsulation approach. The step-wise asymmetric structures and electrical conductivity endow the Ni@MF/CNT/PBAT composites with unprecedented directional EMI shielding performances. When the EM wave is incident from Ni@MF layer or CNT layer, Ni@MF-5/CNT-75/PBAT exhibits the total EMI SE (SE_T) of 38.3 and 29.5 dB, respectively, which illustrates the ΔSE_T of 8.8 dB. This work opens a new research window for directional EMI shielding composites with step-wise asymmetric structures, which has promising applications in portable electronics and next-generation communication technologies.

Steering soft robots in a self-regulated manner remains a grand challenge, which often requires continuous symmetry breaking and recovery steps for persistent motion. Although structural morphology is found significant for robotic functions, geometric topology has rarely been considered and appreciated. Here we demonstrate a series of knotbots, namely hydrogel-based robots with knotted structures, capable of autonomous rolling and spinning/rotating motions. With symmetry broken by external stimuli and restored by self-regulation, the coupling between self-constraint-induced prestress and photothermal strain animates the knotbots continuously. Experiments and simulations reveal that nonequilibrium processes are regulated dynamically and cooperatively by self-constraints, active deformations, and self-shadowing effect of the photo-responsive gel. The active motions enable the knotbots to execute tasks including gear rotation and rod climbing. This work paves the way to devise advanced soft robots with self-regulated sustainable motions by harnessing the topology.