Fabrication And Application Of Intrinsic Self-healing Thin Films Based On Host-guest Layer-by-layer Self-assembly Technology

Layer-by-layer（LbL）self-assembly technology,as a novel technique for preparing nanofilms,enables the controlled preparation of the structure and morphology of the nanocomposite film materials through the material interaction to form the multifunctional self-assembled nanofilm materials.The intrinsic self-healing materials achieve self-healing properties through reversible covalent and non-covalent interactions,which greatly extend the useful life of materials and reduce the potential hazards.Therefore,LbL self-assembly technology applied in the design and preparation of the self-healing multilayer films will enrich the types and functions of self-healing films,and make up for the deficiencies of other technologies,and will also promote the development of the self-healing multilayer films in biomimetic chemical,biological engineering,materials science and so on.In this paper,a variety of polymers were chosen to construct different self-assembled ordered color films and self-healing films via LbL assembly technology.Investigations were made on the structural preparation,optical,self-healing and multifunctional properties of materials above.Moreover,they were also applied in the different fields,such as biomimetic chemical,food engineering,materials science.The main research contents are as follows:1.Combining the advantages of one-dimensional photonic crystal（1DPhCs）,aptamer-functionalized color films（aptamer-TiO₂/P（NIPAM-AA）1DPhCs）were fabricated via LbL assembly technology.The 1DPhCs apta-sensor were applied for the visual detection of heavy metal mercury ions whose detection limit was 5μM.In order to improve the optical response of the 1DPhCs films,the uniform porous films were fabricated at a facile low temperature.It solves the limitation of fabricating uniform porous 1DPhCs materials based on the non-polluting and saving energy,and expands the research area for the need of more applications as well as improves its character.The size of the porous 1DPhCs is below 150nm.More,some environmental response research works were done and it was found that the1DPhCs had better responsiveness to external temperature andβ-glucan.Particularly,these1DPhCs have improved about 2.3 times as responding toβ-glucan than non-porous ones,and the detection limit ofβ-glucan was 0.03 mg/mL.It would be promising as economically colorful sensors in chemical and biological fields.2.In order to introduce the new type of self-healing function,host-guest interation,as a new self-assembly driving,were developed via LbL assembly technology.Beta-cyclodextrin（β-CD）bound with poly（ethylenimine）（PEI）and adamantane（AD）linked with poly（acrylic acid）（PAA）were employed to form a self-healing host-guest film.The obtained highly flexible,acid-resistant,self-healing host-guest transparent multilayer film can easily and repeatedly heal external mechanical damage.The PAA-AD/PEI-β-CD multilayer film enhances the transmittance and mechanical properties of PAA/PEI.The average transmittance was approximately 98.6%,the pre-crack length was approximately 163 mm,and its mechanical property is able to recover to approximately 87.2%.The multilayer film can be self-healing because of the rearrangement and reversible host-guest interactions betweenβ-CD and AD,and its practical utility as curable coatings has been demonstrated.3.After a mild reaction between APP and PEI-β-CD polymers,PAA-AD and APP-co-PEI-β-CD polymers form the novel flame-retardant and self-healing double-network films on paper via the host–guest interaction.The novel film can produce a self-healing surface without any initiating agents.Besides,when directly exposed to a flame,such films will generate foam char layers because of the intumescent effect,and will endow the print paper with a self-extinguishing property.The fire protection of the coatings was intensively investigated by a fire protection test,scanning electron microscopy（SEM）,compressive strength test,thermogravimetric analysis（TGA）,and real-time Fourier transform infrared spectroscopy（FTIR）.It is found that the fire resistant films were found to have the best fire-protection effect under the low-cost and eco-friendly conditions.Therefore,those films have good prospects in the applications of multifunctional advanced commercial supplies,such as papers,textiles,and wood.4.Self-healing,antibacterial and metal-ion sensing coatings with nanosheets were developed using LbL assembly technology via host-guest interaction.The prepared MoS₂/β-CD-PEI/AD-PAA self-healing coatings are not only able to greatly suppress bacterial adhesion and have excellent antibacterial property,particularly kill 99.9%bacteria under UV light irradiation,but also last a longtime service time.Moreover,the self-healing coatings first applied the fluorescence quenching for detecting heavy metals(Co²⁺).Fluorescence spectra demonstrated that a linear relationship existed between the fluorescence intensity and the Co²⁺concentration and the detection limit of Co²⁺was 0.018μg/mL.Therefore,the nanosheets multilayer hybrid coatings would have great potentials in the applications at food industries.