Preparation And Properties Of Amino-Modified PDMS Based Intrinsic Self-Healing Elastomer

Polydimethylsiloxane(PDMS)as one of the high-performance silicone materials has been widely used in strain sensors,e-skins,biomedicine,soft robot and many other fields because of its unique physicochemical properties.However,they are vulnerable to damage in their service life because of their relatively weak mechanical properties.And most current polysiloxane materials don't have the ability to reconstruct the network after damage owning to the irreversible cross-linked structures.Hence,it is meaningful to develop silicone materials with self-healability and reprocessability,which can extend its service lifetime and reduce the energy wastes.Herein,we reported a facile strategy to fabricate intrinsic self-healing transparent PDMS elastomers using a commercial amino-modified silicone as raw materials by introducing reversible imine bond,integrating with polyborosiloxane(PBS)to construct PBS/PDMS double networks and designing a dual cross-linking system based on imine bond and boroxine.After that,we prepared strain sensors by incorporating with electroconductive silver nanowire(Ag NW)and carbon nanotube(CNT)and explored its application in human motions.A self-healing PDMS elastomer(HPDMS)was prepared by introducing the reversible imine bond into the PDMS networks.It has been confirmed the presence of Schiff base reaction and the formation of imine bond by FTIR,Raman and ~1H NMR spectra.The effects of 1,4-diformylbenzene(DFB)concentrations on the gelation process were studied.It can be concluded that the high concentration of DFB may increase the probability of Schiff base reaction.The results of UV-Vis,TGA and DSC showed that HPDMS has a high visible light transmittance,good thermal stability and low glass transition temperature(T_g).The self-healing properties of HPDMS were studied.The results demonstrated the adaptability of the self-healing capability under different environments.The self-healing efficiency can reach 97%after healing 1 h at room temperature.What's more,the elastomer can be reprocessed at room temperature.The mechanical properties of the reprocessed specimens can recover more than 95%compared to the pristine samples.A HPDMS/Ag NW strain sensor was prepared by combining with Ag NW.This sensor has good conductive self-healing capability and shows stable and regular responses to the finger bending.A healable double-network silicon elastomer(PBS/PDMS)was prepared by introducing polyborosiloxane(PBS)into HPDMS networks.The formation of imine bonds and B-O dative bonds was confirmed by FTIR,Raman and ~1H NMR spectra.The results of TGA revealed that after combination with PBS,the decomposition temperature of PBS/PDMS increased 37°C.DSC and UV-Vis results showed that PBS/PDMS elastomer features a low T_g and high optical transmittance.The moisture absorption ability and mechanical properties were studied,and the results showed that the elastomer is stable in moisture.The mechanical properties were dependent on the crosslinking agent content and the stretching speed.The elastomer exhibits excellent autonomous self-healing properties and reprocessability.The self-healing efficiency can reach 98%after healing for 4h at room temperature.And After reprocessing for 2 cycles,the tensile strength could be recovered more than95%.The PBS-PDMS/CNT strain sensor was prepared by transferring CNT onto PBS/PDMS substrate using a vacuum filtration and transfer method.The sensor has good conductive self-healing ability.After 3 cycles of cutting/recycling process,the conductive self-healing efficiency can reach 97%.And the sensor exhibits a stable and continuous response to figer bending.Through the Schiff base reaction between the amino group and the aldehyde group and the dehydration between organoboronic acids,four double-crosslinked self-healing elastomer(PDMS-APB?PDMS-3FPB?PDMS-4FPB and PDMS-FPB)were prepared by introducing the imine bond and the boroxines into the PDMS network.The results of FTIR and ~1H NMR proved that the presence of imine bonds and boroxines.UV-Vis results showed that the transmittance of PDMS-3FPB,PDMS-4FPB and PDMS-FPB is over 82%.The results of TGA and DSC revealed that PDMS-FPB has a higher decomposition temperature 345°C and a lower T_g.Studies on mechanical and rheological properties showed that the cross-linking agent concentration,stretching speed and gage length have a great impact on the mechanical properties of elastomers.The elastic modulus and viscous modulus of the elastomer are both increased with the increase of cross-linking agent concentration.Additionally,because of the dynamic nature of imine bond and boroxine,the double-crosslinked elastomers exhibit excellent self-healing properties and reprocessability.Using PDMS-APB polymer as the raw material,the PDMS-APB/CNT self-healing conductive elastomer was prepared by incorporating with CNT.The elastomer possesses good conductive self-healing properties.It can be used as human motion monitoring sensors to monitor the bending state of finger,wrists,and elbows in real time.And it showed excellent cycle stability.