Self-healing Functional Gels Based On Polymeric Complexes

Because of their special compositions and structures,many polymer gels?bulk gels or gel films?usually exhibit a variety of excellent functions.Polymer gels are inevitably subjected to scratches,repeated deformation and impact during the long-term usage.Due to their soft nature,polymer gels are readily fatigued and physically damaged,which leads to the deterioration of their mechanical properties,loss of original functions and reduction of service life.Therefore,improving the reliability of polymer gels in long-term use and prolonging their service life are highly required in this field.Around these problems,based on the polymeric complexation method developed in our research group,we have successfully fabricated three kinds of polymer gels based on polymeric complexes.By adjusting the compositions of polymeric complexes,reversible interactions and microstructures,the functional composite gels can be endowed with excellent mechanical properties?high mechanical strength,elasticity and toughness,etc.?and self-healing property.Therefore,the reliability and durability of functional composite gels can be significantly improved.The specific researches and their significance are as follows:1.Self-healing polymeric hydrogels with high mechanical strength,excellent resilience and anti-freezing properties are fabricated for application as ionic skins with excellent and reliable sensing performances.The hydrogels are prepared by complexing polyacrylamide?PAAm?with polyacrylic acid?PAA?chelated with Fe³⁺ions followed by shape processing and loading of Na Cl salts.The loading of Na Cl within the hydrogels can generate hydrophobic domains to enhance their mechanical strength and resilience and endow the hydrogels with ionic conductivity as high as0.72 S/m.Because of the synergy of hydrogen-bonding and coordination interactions as well as the hydrophobic domains,the resultant PAAm/PAA–Fe³⁺/Na Cl hydrogels exhibit a high tensile strength of?1.18 MPa and excellent fatigue resistance.The PAAm/PAA–Fe³⁺/Na Cl hydrogel-based ionic skins display quick,reversible and reliable resistance changes with a wide spectrum of strain and pressure sensing capability.The sensing performance of the physically damaged and fatigued ionic skins can be conveniently restored by healing of the PAAm/PAA–Fe³⁺/Na Cl hydrogels under mild conditions.Moreover,the loaded Na Cl greatly decreases the freezing point of water entrapped within the PAAm/PAA–Fe³⁺/Na Cl hydrogels to-24.7 ^oC,which allows the application of the ionic skins at subzero temperatures.2.Highly elastic and ultra-durable ionogel-based ionic condcutors with excellent healability are fabricated through the complexation of vanillin grafted polyvinyl alcohol?VPVA?and 1-ethyl-3-methylimidazolium dicyanamide?IL?and harmless disposal of the ionic conductos are also studied in detail.The ionic conductors?denoted as VPVA-IL?exhibit high tensile strength and strain,being?1.96 MPa and?1253.6%,respectively.Meanwhile,VPVA-IL ionic conductors have excellent resilience and fatigue resistance and can spontaneously immediately recover from a?200%strain to their initial states after the stress release immediately at room temperature.Originating from the non-volatility and high thermal stability of IL and its good compatibility with VPVA,VPVA-IL ionic conductors can maintain long-term stability under high temperature vacuum and high pressure conditions.The ionic conductor-based strain sensors exhibit a high sensitivity to a wide range of strains?0.05–1200%?.Importantly,the VPVA-IL ionic conductors show a highly reproducible electrical response over 8000 uninterrupted strain cycles of 100%.The fractured ionic conductors can be easily healed by heating at 70°C to restore their original ultra-durable sensing performance.The ionic liquid in the ionic conductors can be separated and reused by dialyzing the ionic conductor in water.The new ionic conductor still has excellent mechanical and electrical properties.3.We report the fabrication of self-healing nanofibrillar polymer films with excellent anitifogging property by dip-coating of complexes of poly?acrylic acid?-block-poly?acrylamide??PAA-b-PAAm?and poly?diallyldimethylammonium chloride??PDDA?complexes in an aqueous solution onto solid substrates followed with annealing in a humid environment.The complextion of PAA-b-PAAM and PDDA in solution can lead to the formation of nanorod structures.By dip-coating process,the nanorods in the complex solution will be adsorbed on the surface of substrate and fuse into nanofibers during the drying process of the film.As a proof-of-concept,we demonstrate that the damaged films with a cut of several tens of micrometers wide can perfectly heal the cut as well as the broken nanofibrils.The self-healing nanofibrillar polymer films are highly flexible,transparent and exhibit excellent antifogging ability.Under a humid environment,the antifogging nanofibrillar films can autonomically heal scratches to restore transparency of the films.