Research On The Development And Application Of Polydopamine Coating Properties

Mussel-inspired polydopamine（PDA）exhibits excellent properties such as indiscriminate strong adhesion,good biocompatibility,photothermal conversion,and easy functionalization and modification,showing broad application prospects in many fields including biomedicine,environmental science,sensing,energy conversion and storage.However,there are still some key scientific issues yet to be addressed in the preparation and application of PDA coatings.Firstly,the weak optical absorption of PDA in the visible light region hinders its deep application in surface coloring and photothermal conversion.Due to the inherent chemical heterogeneity of the PDA structure and its unclear complex formation mechanism,to date,there are no direct reports on enhancing the inherent optical absorption of PDA.Another key issue is the poor surface adhesion durability of dopamine（DA）solution.As the aging time of the DA solution extends,the deposition rate of PDA coating on various substrates will rapidly decline,making it necessary to prepare and use the DA solution immediately,severely limiting the practical application of PDA.Therefore,developing a simple and effective method to enhance the inherent light absorption of PDA coating and the adhesion persistence of DA solution has significant theoretical and practical significance.In addition,most traditional methods for preparing PDA coatings are limited to water-based systems,which have poor compatibility with hydrophobic functional molecules and severely restrict the surface functionalization modification of PDA on water-soluble/hydrophobic materials.Therefore,developing a new method for high-efficiency deposition of PDA coatings in organic phases also has significant practical application value.Objective:（1）To develop a novel method to enhance the intrinsic light absorption and persistence of PDA solution by rationally regulating the oxidative polymerization of DA using a simple mixed solvent-mediated strategy.（2）To develop a new type of PDA with low toxicity of melanin to enhance the effect of PDA on human white hair dyeing and operability,and to solve the problem of poor dyeing effect of traditional PDA hair dyeing.（3）Develop a novel method for the efficient synthesis of pure PDA coatings in the organic phase using oxidants-mediated catalysis strategy,which effectively solves the problems of slow polymerization rate of traditional PDA and the synthesis environment limited to aqueous solution.Methods:（1）The oxidative polymerization path of DA induced by sodium periodate is rationally regulated through the introduction of organic solvents,so as to enhance the intrinsic light absorption of PDA coating and the adhesion durability of DA solution.In addition,the PDA solution and PDA coating were analyzed by UV-vis spectrophotometer,the thickness and contact angle of PDA coating were measured by ellipsometer and water contact angle meter,and the morphology of PDA coating was observed by scanning electron microscope（SEM）and atomic mechanical microscope（AFM）.At the same time,the microstructure of PDA in the mixed solvent reaction system was analyzed by means of total reflection Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy（XPS）,ultra-high performance liquid chromatography-high resolution mass spectrometry and density functional theory,which revealed the reason why the mixed solvent mediated strategy improved the performance of PDA coating.（2）Using DA as raw material,on the basis of the developed mixed solvent-mediated PDA coating strategy,a coating with black-like effect was rapidly deposited on human white hair.In addition,using the hematoxylin/metal ion complex as the color enhancer,the paste-like hair dye was prepared by adding a variety of common mechanisms for hair dyeing to further improve the blackening effect and operability,and the hair dyeing effect of the prepared hair dye paste was compared with the commercial hair dye paste.SEM technique was used to compare the morphology of hair before and after dyeing.Colorimeter was used to analyze the color change before and after hair dyeing.（3）Using DA as raw material and Pb（OAc）₄ as oxidant,DA was induced to rapidly oxidize and polymerize in organic solvent to form PDA coatings with good uniformity and stability.By observing the color change of DA solution under different conditions and the corresponding effect of PDA coating,the oxidative polymerization ability of DA was analyzed with UV-vis spectrophotometer.Then the thickness of PDA coating under different conditions was measured by using an ellipsometer to further determine the optimal reaction conditions,and the deposition efficiency of PDA and the adhesion durability of DA solution under the developed organic solvent oxidation catalyst system were investigated.The universality of PDA coating was investigated by using different types of substrates,and the stability of PDA coating prepared by various extreme environmental treatments was studied.The morphology of PDA coating was observed by SEM and AFM,and the elemental composition of PDA coating was analyzed by XPS.Results:（1）By introducing organic solvent,the polymerization path of PDA catalyzed by sodium periodate was effectively regulated,and the intrinsic light absorption and adhesion durability of PDA were enhanced.The characterization results systematically show that the mixed solvent reaction system can effectively accelerate the formation of the cyclized part in the microstructure of PDA induced by sodium periodate,thus contributing to reducing the intrinsic energy band gap of PDA and improving the adhesion durability of aging dopamine solution.In addition,the newly constructed PDA coating rich in cyclized species has excellent surface uniformity and significantly enhanced chemical stability.（2）The developed alcohol/water mixed solvent system significantly enhanced the blackening effect of PDA on the hair surface.At the same time,with the aid of hematoxylin/ferric chloride and the combination of common hair dyeing mechanism,the low toxicity PDA hair dye paste imitating melanin was successfully prepared,which strengthened the black dyeing effect of PDA dye and improved the operability of PDA hair dye.Finally,through the washability test,it was found that the developed low toxicity hair dye with melanin imitation has super strong color fastness,can withstand more than 30 times of shampoo without obvious fading.（3）The oxidation polymerization rate of DA in organic phase can be effectively improved by using the strong oxidation ability of adjacent diol of Pb（OAc）₄.The deposition rate of the prepared PDA coating can reach 47 nm/h,which is the most efficient method to prepare PDA coating in organic phase at present.SEM and AFM results show that the PDA coating has good coverage and evenness.The developed PDA coating strategy can effectively coat on different substrates,which proves the universality of the method.In addition,the PDA coating can remain intact in p H 1 and p H 10 aqueous solutions and various organic solvents,showing good stability.Conclusion:（1）In this study,a new method to enhance the intrinsic light absorption and adhesion durability of polyamine was developed by rationally regulating the polymerization path of polyamine,which significantly improved the absorption and color rendering properties of the material for visible/near-infrared light,and obtained a“blacker”polyamine coating material than natural material.Compared with the traditional method of synthesizing PDA,the newly constructed PDA coating with rich cyclization species not only shows significantly enhanced inherent light absorption ability and more durable surface deposition performance,but also has higher uniformity and better chemical stability.In addition,this work systematically explored and successfully elucidated the potential mechanisms of inherent light-absorbing properties,surface morphology changes,and enhanced adhesion persistence of PDA.This study not only contributed to a deeper understanding of the inherent relationship between the structure and properties of PDA but also provided new ideas for the rational design and application of advanced functional PDA coating materials.（2）Based on the novel PDA coating technology mediated by mixed solvents,the application potential of PDA as a high-performance permanent hair dye was further validated,and the technology was successfully applied in hair coloring.Due to the excellent coloring performance of the PDA coating in the alcohol/water mixed system,better hair coloring effect was achieved on natural fading white hair compared to traditional PDA hair dye.In addition,the strong chelating effect between PDA and metal ions,as well as the strong color enhancement performance of the mordant-sensitized metal ion/PDA composite,further enhanced the black dyeing effect of PDA hair dye,and it is expected to replace traditional aniline hair dyes with strong sensitizing and potential carcinogenicity.（3）In this work,a simple and fast PDA coating strategy has been successfully developed in the organic phase.Pb（OAc）₄ was used to induce the rapid oxidation polymerization of DA in organic solvents,and to deposit high-quality PDA coatings with good uniformity and stability on various substrates.This method avoided the extensive use of organic bases and the doping effects on PDA structure,not only solving the problem of traditional PDA synthesis limited to aqueous solutions,but also effectively improving the deposition rate and surface adhesion of PDA coatings in organic phases.The developed method of Pb（OAc）₄-induced PDA coating has broad application prospects in the modification of hydrolytic/hydrophobic materials surface and other fields.