Synthesis And Properties Of Automous Self-healing Polymers Based On Dynamic Non-covalent Bonds

Living organisms are able to recover from injuries to resume active and reproductive functions.The ability to continue these metabolic processes determines the longevity of their existence.Synthetic materials are designed to be functional,but do not possess metabolic attributes.To prolong their lifespan,the concept of selfrepairing has been explored and became the central topic of scientific interests and technological significance.So far,various reversible bonds or dynamic interactions have been utilized for self-healing materials.The reversible covalent bonds(such as alkoxyamine,disulfide)or crosslinking reaction(such as Diels-Alder reaction,radical dimerization reaction,cycloaddition reaction)can lead to repeatable healing.However,the healing of such materials always requires the input of external energy such as heating,light irradiation,or addition of catalyst,reducing or oxidizing species.This work aims at synthesis of autonomous self-healing materials.Pt…Pt interaction is a typical attractive metallophilic interaction that exists among platinum(?)atoms.In this work,we incorporate a C^N^N cyclometalated platinum(?)complex into a polydimethylsiloxane(PDMS)matrix.The molecular interactions between cyclometalated platinum(?)complexes(Pt…Pt and ?-? stacking interactions)are strong enough to crosslink linear PDMS polymer into a film with high mechanical strength.The film displays excellent stretchable properties and can heal completely both in tensile modulus and modulus of toughness after 12 h at room temperature without any external stimuli.On the basis of the above work,we incorporate a fluoro-N^C^N cyclometalated platinum(?)complex into a polydimethylsiloxane(PDMS)matrix.Hydrogen bonding is added to the polymer,as well as the reinforced Pt…Pt and ?-? stacking interactions.The film displays more elastic and tough properties and can also heal at room temperature without any external stimuli.Our results suggest that the stretchability/elasticity and superb self-healing properties can be obtained simultaneously without any conflict by optimizing the strength of crosslinking interactions.Europium complexes exhibits excellent optical properties.Herein we report a Eu(?)complex with a photosensitive ligand.The as-prepared ring open conformation is colorless and highly emissive,due to efficient energy transfer from.Upon UV light irradiation,the ligand turns into closed form with decreased triplet energy thus blocked the energy transfer.The ring closed conformation is red and non-emissive.Based on these results,we developed a multi-stage transparent security ink which is more difficult to be counterfeited compared to single-stage inks.Moreover,combined with the unique photo-responsive properties of the ligand,we demonstrated a double encryption method.On the basis of this complex,we further incorporate a photosensitive europium complex into a polydimethylsiloxane(PDMS)matrix.The as-prepared film also displays photochromic property and can be used to encryption process.Moreover,the film shows excellent self-healing properteties at room temperature.These materials can find applications in wide range of field such as protective coatings,sealing agents,electronic skins and artificial muscles.