Supramolecular Elastomer And Hydrogel With Excellent Healability

Self-healing polymeric materials are capable of healing their mechanical damages either spontaneously or under the assistance of a stimulus.Developing self-healing materials is significant to prolong lifespan of materials and to enhance their stability and safety.The research progress on self-healing materials concentrates on higher healing efficiencies,superior mechanical properties and convenient fabrication.Supramolecular interactions have gained extensive attention in the field of self-healing materials because of their highly reversibility,directionality and sensitivity,which are beneficial to adjust the repair performance,mechanical properties and functions of materials.In this thesis,self-healing materials with excellent healability are studied.We focused on three subjects of self-healing materials:first,how to improve the repair efficiency of materials and reduce the reliability of external stimulus;second,how to prepare the mechanically robust materials with admirable self-healing ability;third,how to improve the self-healing ability of materials without loss of functional performance.The research contents are as follows:1.We present the fabrication of biomass-derived self-healing elastomers with rapid room temperature self-healing ability.The self-healing elastomers(Mⁿ⁺/POA–His)are first synthesized by grafting histidine onto poly?oleic acid??denoted as POA–His?,followed by crosslinking POA–His with transition metal salts.The identity of metal ions determines the strength of coordination bonds.Thus,the mechanical properties and self-healing abilities of the Mⁿ⁺/POA–His polymers can be readily controlled by the variation of metal ions.Due to the reversibility of coordination bonds and the branched structure of POA–His,the Mⁿ⁺/POA–His polymers exhibits excellent self-healing ability.After only 10 s of contact,the healing efficiency of Zn²⁺/POA–His,which is defined as the ratio of the restored tensile strength to the original one,is calculated to be 59%.Healing at room temperature for 1 h led to a complete healing of the Zn²⁺/POA–His.Additionally,the Mⁿ⁺/POA–His polymers could not only be recycled multiple times by hot pressing but could also be recycled by replacing the metal ions in the Mⁿ⁺/POA–His polymers.Owing to their tunable mechanical properties and self-healing ability,the Mⁿ⁺/POA–His polymers have a potential application as sealant.We believe that all the aforementioned characteristics of Mⁿ⁺/POA–His polymers demonstrate the feasibility and advantages of preparation of self-healing elastomers via renewable natural resources.2.We present the fabrication of a self-healing elastomers by attaching carboxyl group to polybutadiene,followed by cross-linking through the metal coordination interaction between Zn²⁺and carboxyl group(The resulting materials are denoted as PB-COOH/Zn²⁺).The PB-COOH/Zn²⁺has admirable mechanical properties and exhibits tensile stress of 6.30 MPa,ultimate strain of 2284%,Young's modulus of 1.68 MPa and toughness of 68.66 MJ/m³.Benefitting from high mobility of the polymer chain and excellent dynamic performance of the metal coordination interaction,PB-COOH/Zn²⁺has excellent self-healing ability.The mechanical properties of the damaged PB-COOH/Zn²⁺almost completely recover after healing at 70? for 3 h.The healing efficiency of PB-COOH/Zn²⁺,which is defined as the ratio of the restored toughness to the original one,is 100%.By investigating the self-healing properties,we believe that higher temperature can speed up the healing process.The mechanical properties of the damaged samples only need 1 h to achieve complete recover at 90?.In addition,the PB-COOH/Zn²⁺has excellent recycling abilities under mild conditions.PB-COOH/Zn²⁺can be reprocessed by hot pressing at 70? with the pressure of 5 MPa for 10 min.The recycled PB-COOH/Zn²⁺still maintains quite stable mechanical properties after three reprocessing processes.The mechanical properties of the metal coordination elastomers can be further improved by doping PB-COOH/Zn²⁺with MWCNTs.The Young's modulus of the PB-COOH/Zn²⁺doped with 40wt% MWCNTs(denoted as PB-COOH/Zn²⁺/MWCNTs-40)is improved to 8.21 MPa.After doping with MWCNTs,the result elastomers maintain good the self-healing and recycling abilities.The conductivity of MWCNTs endows the PB-COOH/Zn²⁺/MWCNTs with potential to transduce electrical energy into Joule heating energy to accomplish electro-thermal healing process and sensing application,which extend its potential applications as environmental-friendly materials.3.We present the fabrication of transparent polymeric films that are capable of healing millimeter-scale cuts by incorporating hydrogen-bonding units into zwitterionic polymer films,which are cross-linked by electrostatic interactions.The self-healing transparent films are prepared via the TiO2-catalyzed random copolymerization of[2-?methacryloyloxy?ethyl]dimethyl-?3-sulfopropyl?ammonium hydroxide?MSA?and 2-acrylamide-2-methylpropanesulfonic acid?AMPS?.Compared with bulk materials,films are more difficult to heal due to the limitation of the substrate.In this part,the healing ability of the PMSA-co-AMPS_n films can be mediated by the AMPS content in the resultant films duo to the weak strength and the water susceptibility of the hydrogen-bonding interactions.Specifically,the PMSA-co-AMPS_0.2 films are capable of healing a cut with a width of 7.9 mm,whereas the PMSA films can only heal a cut with a width of 110?m.Furthermore,the PMSA-co-AMPS_n films can readily clean up oily contaminants in water because of the strong water-binding ability of the zwitterionic MSA units.In addition,the PMSA-co-AMPS_n films can conveniently restore their damaged transparency and oil-cleaning ability because of their promoted healing ability,thereby prolonging the life span and reliability of the films.