Conductive Self-healing Material Based On Hydroxyl-terminated Polybutadiene Crosslinked By Reversible Boron-oxygen Bond

During application,the conductive materials are inevitably damaged by external forces or environmental aging,leading to failure of electric circuit or even serious accidents.It is urgent to study the conductive materials with self-healing ability to reduce unnecessary loss and wastes.In this thesis,conductive self-healing materials were prepared by using multi-walled carbon nanotubes(MWCNTs)as the conductive agent,hydroxyl terminated polybutadiene(HTPB)as the matrix,which was crosslinked by reversible boron/oxygen linkages.The mechanical and electric healing ability were investigated.This research work is majorly composed of three parts.In the first part,2,2'(1,4-Phenylene)-bis[4-mercapto-1,3,2-dioxoborane](BDB)was synthesized by the reaction between 1,4-phenylboronic acid and thioglycerin at first.HTPB was crosslinked by BDB via "thiol-ene" click reaction.MWCNTs were mixed with HTPB/BDB to prepare room-temperature conductive self-healing composites.About 97.8%of conductivity was recovered for the composite sample containing 7 wt%carbon nanotubes after repairing for 8 minutes at 25?.In addition,90.4%of the initial mechanical strength was recovered after repairing for 1 hour.Moreover,these composites had flexible conductivity,temperature responsibility and electromagnetic interference shielding properties.In the second part,a kind of self-healing polymer was prepared by the reaction between boric acids and hydroxyl groups of HTPB.MWCNTs were mixed with the polymer thereafter.Low-temperature self-healing conductive composites were prepared because HTPB has a very low glass transition temperature.About 98%of the conductivity was recovered for the composite sample containing 7 wt%carbon nanotubes after repairing for 5 minutes.In addition,about 87.6%of the initial mechanical strength was recovered after 24 hours of reparation.Moreover,these composites had low-temperature flexible conductivity,temperature sensitivity and electromagnetic interference shielding properties.Finally,a self-healing polymer containing HTPB crosslinked by both BDB and boric acid was prepared.Thereafter,a new kind of self-healing conductive composite was obtained by mixing MWCNTs.Performances of the composite were investigated,including the mechanical property,self-healing property,electrical conductivity and electromagnetic interference shielding property.In this thesis,the influences of different kinds of borate ester linkages were investigated,on the mechanical and electric properties of conductive self-healing composites composed from HTPB.Their flexible conductive ability,temperature responsibility and electromagnetic interference shielding property were investigated as well.The research results are good references to the design and synthesis of conductive self-healing composites based on borate ester linkages and HTPB.