Fabrication And Application Of Layer-by-Layer Assembly Self-healing Films

Self-healing materials can repair themselves thus greatly extend the service life and reduce the potentially dangers of the materials during use,which promise to greatly broaden the future applications in major project and leading edge technology.Layer-by-layer(LbL)assemble technique has attracted more and more attentions because the widely used thin films can be conveniently prepared by this method.The LbL assemble technique is also used for fabricating films with special structure and morphology,for LbL assemble technique can be driven by multiple weak interactions.In this paper,we take advantages of the LbL assemble technique,choose a variety of polyelectrolytes to fabricate the self-healing multilayer films and fully exploring their applications in different areas.(1)Based on LbL assembly technique,branched poly(ethyleneimine)(bPEI)and poly(acrylic acid)(PAA)were modified on carbon fiber paper surface to fabricate the corrosion resistance coatings.The prepared coatings not only can protect the carbon fiber from corrosion,but also can take advantages of the surrounding water to quickly repair themselves after damaged.The effects of assembly cycles on morphology,resistance,air permeability and the contact angle of carbon fiber papers were investigated,then the differences of the carbon fiber papers in electrolysis process were explored.The results reveal that all the coatings can protect carbon fiber papers from corrosion,while when the assembly cycles was 10,the coating are more efficient.(2)Combining loading property of the microcapsules and healing function of polyelectrolyte multilayer films,based on LbL assembly technique,a novel antimicrobial coating was fabricated by alternating depositing bPEI,PAA and drug loaded microcapsules.The results indicate that the coating has excellent long-term antibacterial properties,what is more,it has good self-healing ability,can restore the original mechanical properties and the antibacterial properties of the coating after damaged.Given that the microcapsules can embody different types of functional molecules,thus this work offers a new solution to fabricate the different types of desired functional self-healing coatings.(3)Firstly,the possible specific structural parameters of the various hydrogen bonds between chitosan(CS)and PAA were calculated.Then,polyelectrolyte multilayer films were fabricated with CS and PAA based on LbL assembly technology.The possible influence factors on the self-healing ability of the film were investigated.The results show that the interactions between CS and PAA,swelling capacity,microstructure and wettability are all governed by the pH of the CS solution.When the pH value of the CS solution is 3.0,the prepared multilayer polyelectrolyte film has excellent self-healing ability.(4)Based on intermolecular hydrogen bonding and metal-ligand coordination,the synthetic strategy involves of LbL assembly technique,a humidity-responsive self-healing colorful polyelectrolyte multilayer composite film was designed and fabricated.Firstly,the conformations of CS/PAA and Co-CS/PAA were investigated by molecular simulation method.Furthermore,the impact of cobalt on the chemical and physical properties of the films were characterized.Then the self-healing process and humidity response performance of the film were observed.The results show that cobalt chloride annealing treatment plays a critical role to rebuild the reversible interactions that facilitate the film to heal the mechanical damages,and endow film with the property to change its color reversibly in different humidity conditions.(5)The first example of color tunable,ultrathin film capable of healing damage caused by mechanical abrasion was presented based of previous research on photonic crystals of our group.It was designed with intermolecular hydrogen bonding,the synthetic strategy involves spin-coating of PAA and CS which have large refractive index difference.The colors of the ultrathin self-healing films are tunable,scratches on the films caused by mechanical abrasion can be completely repaired by immersing the films in the solution that pH at 2.5,and their original color can also restored.Importantly,the healing process can be repeated multiple times for different damage events in a given region.