Fabrication And Application Of Schiff-base Bonded Self-healing Films

Animal or plant skin can heal itself after being injured by external mechanical damage which indicate the scientists to design a new type of functional material:self-healing material.Worldwide interest has been gained toward self-healing materials in recent years because self-healing property can offer many new and potential applications under various conditions.According to healing mechanisms,self-healing materials can be divided into two kinds of materials:extrinsic self-healing materials,which complete their self-healing process via healing agents,and intrinsic self-healing materials,which are based on dynamic,reversible linkage/reaction,such as hydrogen bond and coordination bond.In this work,dynamic Schiff base linkage is introduced to self-healing material.The self-healing mechanism and the application are studied.The detailed work are as follow:（1）We have demonstrated the fabrication of（CS/DF-PEG）_n film with high transparency and self-healing property based on LbL technique.The dynamic linkage in Schiff base-bonded（CS/DF-PEG）_n film endows the film with self-healing property.The transparent（CS/DF-PEG）_n film,whose transmittance is ～99.4% at average,can heal damages of～200μm wide that penetrates to the underlying glass substrate.Moreover,the（CS/DF-PEG）_n film can heal such damages for ten times in the same location.The（CS/DF-PEG）_n film can heal cuts not only to maintain structure of the film,but also to keep its transparency.The transmittance of the healed film can remain at 99.0% after ten damage/healing processes.The combination of self-healing property and high transparency provides not only a new way to the design of optically transparent films with self-healing ability to extend service life,but also a new method to solve the problem that functional materials can only go through a few damage/healing processes..（2）We have demonstrated the fabrication of colorful（DF-PEG/CS）_n film with the ability to heal damages by spin-coating method.The factors that influence the self-healing ability of colorful（DF-PEG/CS）_n film are investigated.The results show that the healing ability of（DF-PEG/CS）_n films is film thickness dependent.Contact angle（CA）which represents wettability of material also has impact on the self-healing ability of colorful（DF-PEG/CS）_n film.When CA is above certain angle-about 50°,the film cannot heal damages.Furthermore,the sensor array consisting of six（DF-PEG/CS）_n films with different structural color is able to recognize different divalent metal ions.（3）We report a double-network self-healing film for gas separation which is built by chitosan,dialdehyde starch,and polyvinyl alcohol.Gas separation membranes have been studied in recent years.However,few self-healing materials have been applied in gas separation membranes,which suffer in harsh environments and show none self-healing ability.We prepared a self-healing gas separation film which is built by Schiff base linkage and hydrogen bond.CO₂ separation properties of self-healing gas separation film with different water content are measured.Meanwhile,according to results,the higher cross-link density,the better self-healing ability.The combination of gas separation property and self-healing property provides a new way to improve the lifetime of gas separation films.（4）Here,we report a series of novel anticancer self-healing double-network films.The first network is the Schiff base linkage and the second one is the metal coordination-chelation interaction.Different metal coordination-chelation interactions which will influence the fluidity of the Schiff base linkage are introduced.The influence of the fluidity of the Schiff base linkage to the self-healing ability of the film is studied.According to results,the better fluidity of the Schiff base linkage,the higher self-healing ability film has.The antibacterial and anticancer activities of the double-network films are investigated.Based on the advantages of layer-by-layer assembly technology,this paper selects polyelectrolyte materials to construct self-healing films based on Schiff base linkage.Factors influencing the self-healing property of films,including the thickness of film,the cross-linking density and mobility of the linkage,are studied.Schiff base-bonded self-healing film is used as sensor,gas separation membrane and antibacterial coating,which widen the application of self-healing materials in different fields.