| Graphene,constructed from sp~2-bonded carbon atoms,is a two-dimensional（2D）,single-atom thick planar sheet with a honeycomb crystal lattice.It has high proton conductivity,superior mechanical properties,excellent thermal stability,and high surface area which collectively make graphene a very promising material for reinforce the electrical and mechanical properties of polymers.Graphene/polymer composites have a wide variety of applications that include electromagnetic shielding,energy storage,supercapacitors,sensors,oil-water separation and photothermal conversion.Reduced graphene oxide（rGO）is a graphene derivative obtained via reduction of GO with properties close to graphene.Compared with graphene,rGO has a simple preparation method,low polarity and higher chemical activity.As a commonly used polymer matrix,silicone rubber has the advantages of high elasticity,high tensile strength,transparency,and biocompatibility.rGO/silicone rubber composites have broad application prospects in the fields of electronic devices,medical devices,and industrial buildings.However,rGO/silicone rubber composites with uniform filler dispersion,perfect filler network and good filler-matrix interface compatibility by traditional mechanical blending and solution blending are difficult to be prepared,due to the low polarity and poor chemical activity of silicone rubber.Based on the consideration of the above problems,in this paper,rGO/PDMS functional composites with different structures and properties were prepared by different fabrication processes with polydimethylsiloxane（PDMS）as the matrix and rGO as the functional filler.1.The rGO/PDMS composites with three-dimensional（3D）filler network were fabricated by backfilling polymer matrix into the preformed porous conductive filler skeleton.Based on the electrostatic and hydrogen bonding interactions between natural cationic polymer chitosan（CS）and GO,a hybrid CS-rGO aerogel（CGA）was fabricated by integrating a one-pot hydrothermal strategy and freeze-drying rGO aerogel.The micromorphological characterization of CGA confirmed that the formation of its assembling structures of a three-dimensional continuous network,and the interaction between rGO and CS enhanced the interfacial compatibility between rGO and CS.In addition,CS which is a green reducing agent forGO and hydrothermal reduction have a synergistic effect to reduce GO,improving the reduction effect further.After that,PDMS was backfilled into the CGA three-dimensional filler network to prepare CS-rGO/PDMS（PCGA）with good dielectric properties.The dielectric constant increases from 34.1 to 297.3 with the increase of rGO content,while the dielectric loss always stays between 1-2,at the frequency of 100 Hz.The conductive rGO to increase the dielectric constant while effectively blocking the leakage current with insulating CS to mitigate the dielectric loss,thus ensuring the balance between dielectric constant and loss.Finally,PCGA was assembled as a capacitive sensor and its capacitive sensing properties were investigated.The results indicated that the sensor possesses a desirable integration of high sensitivity(0.058 k Pa-1 in the pressure range 0-7 k Pa)and wide work range（0-140 k Pa）due to the synergistic effect of the excellent mechanical performance along with high dielectric constant and suppressed loss.Moreover,numerous actions,such as walking,elbow flexions and pressing could be efficiently monitored in real time using this capacitive sensor.2.A PDMS sponge matrix skeleton with porous structure was fabricated with soft white sugar as a template.PDMS multifunctional sponge were fabricated by impregnating and adsorbing fillers.To enhance the interaction between the active filler and the PDMS sponge skeleton,the bioadhesive polydopamine（PDA）was selected to modify the PDMS sponge to enhance its chemical activity.Afterwards,a three-dimensional conductive active layer of rGO-CNT was formed on the surface of the PDA-modified PDMS sponge（PDMS-PDA）by dipping method to enhance the conductivity of the PDMS sponge.The electrical conductivity of rGO-CNT/PDMS-PDA sponge can reach 1 S/m which indicate an excellent electrical conductivity.The rGO-CNT/PDMS-PDA sponge was assembled into a piezoresistive sensor and characterized its sensing properties.The results indicate that the sensor can detect different pressures and strains.The sensor has a sensitivity of 0.3 k Pa-1 at a low pressure of 500 Pa.It can be applied to smart wearable flexible electronic devices and other fields.In addition,benefiting from the hydrophobic light absorbance of rGO and CNT,the rGO-CNT/PDMS-PDA sponge has excellent oil-water separation ability and photothermal conversion performance（irradiated under sunlight with a power density of 1 k W/m~2 for 2 min,its temperature can reach77.9℃）.3.The rGO/PDMS composites with stable 3D filler network were fabricated by a novel and efficient strategy on the latex assembly technique and in-situ reduction.Due to the steric repulsion of latex particles,rGO is confined at the interface of latex particles,forming an interconnected 3D structural conductive network.Herein,benefitting from the 3D rGO filler network,the rGO/PDMS can achieve the percolation threshold with a low amount of rGO for efficient electron transport at low rGO loadings,which endowing it excellent flexibility and mechanical deformability.As a result,the strain sensors base on the rGO/PDMS films showed superior sensitivity（44.01）,a ultrawide strain range（300%）and good stability（2500 cycles）.Besides,the sensor has potential applications in human health monitoring fields such as sensing finger movements,facial muscles,speech recognition,and physiological signals. |
