Self-Healing Shape Memory Polymeric Materials And Flexible Devices

Shape memory polymers?SMPs?that can fix a temporary shape and return to their permanent shape under an external stimuli,such as heat,light,electric and magnetic field.This unique property enable SMPs to have promising applications in various areas,including deployable space equipment,biomedical devices,electronic instrument,textile products,and so forth.However,SMPs are prone to mechanical damage because they unavoidably undergo various kinds of deformations,accidental scratches in their practical applications.These mechanical damages will severely decrease the reliability and shape memory performances of the SMPs,and even result in their failure.Therefore,it is important to intergate self-healing ability to shape memory polymers to extend their service life and enhance their reliability.Self-healing SMPs can be fabricated by inducing noncovalent interactions,dynamic covalent bonds,and healing agents in to SMPs.In this thesis,we aim to fabricate self-healing SMPs with different properties by adjusting their composition and reversible interactions and explore their functionalization,the specific research contents are shown as follows:1.We demonstrate that thermally and NIR-light-induced shape memory polymers with self-healing ability and satisfactory mechanical robustness can be fabricated by dispersing poly?acrylic acid??PAA?-grafted graphene oxide?GO??PAA-GO?into polyvinyl alcohol?PVA?matrix.The PVA/PAA-GO_3%films with a PAA-GO content of 3.0 wt%have a fracture stress of⁷0.4 MPa and a Young's modulus of².8 GPa.The PVA/PAA-GO_3%films exhibit an excellent shape memory performance because PVA and PAA-GO form a stable network through hydrogen-bonding interaction between them.Meanwhile,the PVA/PAA-GO_3%films are capable of recovering from temporary shape to permanent shape under NIR light irradiation because of the excellent photothermal conversion property of the GO nanosheets.More importantly,benefiting from the reversibility of hydrogen-bonding interactions between PVA and PAA-GO nanosheets,the shape memory PVA/PAA-GO_3%films are capable of healing physical damage and the fatigued shape memory function with the assistance of water,which greatly enhance their reliability as shape memory materials and prolong their service life.2.We demonstrate the fabrication of healable muti-shape memory polymers by complexing PBA and PVA.The PVA/PBA_2%films with a PBA content of 2.0 wt%have a fracture stress of⁵5.9 MPa and a Young's modulus of¹.7 GPa.The PVA/PBA_2%films exhibit an excellent shape memory performance because PVA and PBA form a stable chemical network through boron ester bond between them.Besides,PVA/PBA_2%films demonstrate mutishape-memory effect based on a broad glass transition temperature.More importantly,benefiting from the reversibility of the boron ester bond between PVA and PBA,the shape memory PVA/PBA_2%films are capable of healing physical damage with the assistance of water,which greatly enhance their reliability as shape memory materials and prolong their service life.3.We report a healable and shape-editable supercapacitors that fabricated by sandwiching poly?acrylic acid?-poly?ethylene oxide??PAA-PEO?hydrogel electrolytes between two pieces of carbon nanotube?CNT?-coated polyurethane-poly??-caprolactone??PU-PCL?electrodes.The flexible,healable and shape-editable supercapacitor delivers a specific capacitance³7 F g^-1 at a scan rate of 0.5 A g^-1 and exibits an outstanding cycling performance with a capacitance retention of⁹6.5%after 10000 charge/discharge cycles.Because of the healability of PU-PCL substrates and PAA-PEO hydrogel electrolytes,the fractured supercapacitors can heal physical damage and restore⁹2.6%of its original specific capacitance after5 cutting/healing cycles.Moreover,benefiting from the shape memory ability of PU-PCL substrates,the supercapacitors can be shape-edited to desired shapes with a high shape fixing and recovery ratio,and displays a negligible decay in specific capacitance during repeated shape-editing process.The integration of healability and shape-memory function into flexible supercapacitors can not only expand their working conditions,but also expand their lifetime and enhance their reliability.