Functional Polymeric Films With Healability:Antifouling,Antifogging And Proton Conduction

Polymeric materials generally exhibit various remarkable functionalities because of their unique composition and structures.Compared with inorganic antifogging films,polymeric materials possess lower modulus as well as hardness and are prone to mechanical damage in practical usage.These damaged materials will lose their original remarkable functions,leading to a serious impact on our production and life.Therefore,one of the most effective approaches to extend the service life and enhance the reliability of fucntional polymeric films is to endow them with the ability to heal scratches.Self-healing polymeric materials have been widely fabricated by utilizing reversibility of noncovalent interactions and dynamic covalent bonds.In this thesis,we focus on endowing various functional polymeric films with excellent self-healing property by adjusting the composition and reversible interactions in the films.Meanwhile,the stability of the as-prepared films is improved by a series of post-treatments without affecting their self-healing properties.This thesis achieves the mass production of self-healing functional films in a facile and time-effective method.Furthermore,the thesis carries out initial exploration in the fabrication of self-healing functional films that can heal themselves under their working conditions.1.We demonstrate that healable antifouling films capable of healing deep and wide cuts can be fabricated by the layer-by-layer(Lb L)assembly of partially hydrolyzed PEtOx(PEtOx-EI)and polyacrylic acid(PAA)based on hydrogen-bonding interactions as the driving force.The stability of the hydrogen-bonded LbL-assembled films is improved by thermally cross-linking the secondary amine groups in PEtOx-EI and the carboxylic acid groups in PAA.A high concentration of partially hydrolyzed PEtOx on the film surface gives the Lb L-assembled PAA/PEtOx-EI films the ability to inhibit the adhesion of both Gram-negative and Gram-positive bacteria.Moreover,the PAA/PEtOx-EI film can heal scratches and cuts several tens of micrometers wide after being immersed in water to restore the original antifouling function of the film in the damaged regions,thanks to the dynamic nature of hydrogen-bonding interactions between PEtOx-EI and PAA as well as the high mobility of polymer chains in the antifouling films.2.We demonstrate the fabrication of healable antifogging and frost-resisting films by dip-coating hydrogen-bonded polyvinyl alcohol(PVA)-Nafion complexes.The stability of the PVA-Nafion composite films in water is significantly improved by soaking the as-prepared films in an aqueous NaOH solution to induce the crystallization of PVA in the films.The PVA-Nafion composite films exhibit excellent antifogging and frost-resisting properties even under aggressive fogging and frosting conditions.In addition,the PVA-Nafion antifogging film can quickly heal scratches and cuts several hundreds of micrometers wide(10 times larger than the film thickness)upon exposure to water to restore their original antifogging and frost-resisting properties.The dip-coating of PVA-Nafion complexes provides a facile way to fabricate healable antifogging films with extended service life that are capable of being deposited on various substrates.3.We report the first example of intrinsic healable PEMs capable of healing mechanical damage and restoring their original proton conductivity and methanol resistance in working conditions of direct methanol fuel cell(DMFCs)by complexing Nafion with PVA followed by post-modification with 4-carboxybenzaldehyde(CBA).Compared with Nafion membranes,the CBA-modified Nafion-PVA composite membranes exhibit improved cell performance.More importantly,the CBA-modified Nafion-PVA PEMs can heal holes and cuts several tens of micrometers wide that penetrate through the whole membranes under the working conditions of DMFCs to restore their original mechanical robustness and cell performance.