| Three-dimensional porous graphene materials are widely used in the field of flexible piezoresistive materials because of its high elasticity and abundant porous structure.At present,researchers often use flexible polymer materials(such as rubber,polyurethane,polydimethylsiloxane,etc.)as a matrix,and graphene oxide(GO)sheets are deposited on the polymer matrix or skeleton by chemical vapor deposition,dipping,pulling,and freezing casting,and the three-dimensional porous graphene materials are obtained after reduced.However,due to the strong ?-? interaction between graphene sheets and the existence of van der Waals forces during the preparation process,the graphene sheets are prone to irreversible agglomeration,which weakens the bonding between the polymer matrix and the graphene sheets,and damages the structure of the three-dimensional porous graphene.As a result,the flexible piezoresistive sensing performance of such three-dimensional porous graphene materials often has problems of low sensitivity and long response time.Based on this,methods for constructing threedimensional porous graphene materials with special pore structure were proposed,the microstructure,mechanical properties,sensing properties and superhydrophobic properties of these two kinds of reduced graphene oxide/polyurethane composite sponges were investigated.The main findings are as follows:Reduced graphene oxide/polyurethane composite sponge with special pore structure was prepared by combining thermal induction method,template method and chemical reduction method.Reduced graphene oxide /polyurethane composite sponge(GPCS-LAA)was prepared by using polyurethane as the basic skeleton,alkyl polyglucoside as the foaming agent to form GO microbubble aggregate,and ascorbic acid(LAA)as the reducing agent.It was found that under the thermal-induced condition,the microbubbles of the GO microbubble agglomerate ruptured inside the PU skeleton,so that the graphene oxide(GO)on the microbubble surface was well sprayed on the PU skeleton,which prevented the agglomeration of GO from blocking the PU pores,thus forming a special structure of "pore within pore".At the same time,the thermal induction provides suitable temperature conditions for the reduction of GO by LAA,which simplifies the preparation process of GPCS-LAA and enables the successful reduction of GO in PU skeleton by LAA.The flexible stress-strain sensor based on GPCS-LAA has a sensitivity as high as 2.9?4.0,is capable of detecting pressures as low as 10 Pa,has a response time as low as 35 ms,and can stably perform 5000 cycles of load-unload cycle detection.After further assembly,the GPCS-LAA-based wearable sensor can monitor human motion such as elbow bending and finger flexion in real time and accurately.For the practical application of three-dimensional porous graphene materials in harsh environments,such as moisture,stains,and corrosive conditions,we have studied a reduced graphene oxide/polyurethane composite sponge with both superhydrophobicity and flexible piezoresistive properties,using polyurethane as the basic skeleton and dodecyl glycoside as the foaming agent to form GO microbubble agglomerates,and the GO microbubble agglomerate/polyurethane composite sponge was subjected to extremely rapid by freezing the GO microbubble agglomerate/polyurethane composite sponge with liquid nitrogen,a graded pore structure is formed in the PU,and then the graphene/polyurethane composite sponge(GPCS-HHA)is obtained by hydrazine vapor reduction.The GPCS-HHA-based flexible stressstrain sensor has a sensitivity of up to 3.8,a response time as low as 45 ms,and the ability to stably detect changes in resistance at different strains.During the GPCS-HHA bending-release process,the current flowing through the GPCS-HHA also makes corresponding changes in real time and steadily.In addition,GPCS-HHA has good superhydrophobicity with WCA up to152.5 °,which has potential application in the complex environment such as wet and underwater. |
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