Preparation And Application Of Polydopamine - Assisted Organic - Inorganic Composites

In recent years, mussels, the underwater fouling organisms, are able to achieve a long-lasting adhesion in a wet environment and attach to any natural or synthetic substrates based on the adhesive proteins secreted by the byssus of the mussels. Most of the evidence has demonstrated that a large amount of 3,4-dihydroxyphenyalanine (DOPA) is in the adhesive proteins secreted by mussels, which is the main reason of the strong adhesion force. Dopamine as one kind of DOPA derivatives has the similar structure and properties with DOPA, and can also realize the adhesion on the surface of the base materials, thus caused the great attention of researchers. In this study, based on the understanding of the structure, properties and polymerization mechanism of dopamine, a thin surface-adherent polydopamine (PDA) coating onto various surfaces through the self-polymerization of dopamine in alkaline and aerobic environment has been obtained. Polydopamine can realize the functionalized modification on the surface of the base materials by their strong adhesion performance. These formed polydopamine coatings have an ample amount of active catechol and amine groups, which can be served as a universal platform for the preparation of polydopamine composite materials with different functions. By studying the structure-activity relationship between structures and material performance of polydopamine composite materials, we can provide theoretical basis for their applications in different fields. All the research contents and results are shown as follows:(1) Silicon wafers were choosed as substrates, and polydopamine films were formed on their surface by the self-polymerization of dopamine. Polydopamine films have plenty of active catechol and amine groups, which can serve as a organic matrix to control the mineralization of calcium carbonate. CaCl2 solution was used as the calcium source and CO2 was provided by the decomposition of (NH4)2CO3. The mineralization of calcium carbonate can be controlled under the synergy of polydopamine and poly(acrylic acid) (PAA), and finally formed polydopamine-calcium carbonate organic-inorganic composite coatings. SEM, XRD, IR were used to analyze the morphology, surface composition and crystalline structure of calcium carbonate mineralized after different days and proposed the formation mechanism of calcium carbonate films.(2) The monodisperse polystyrene (PS) spheres were synthesized via dispersion polymerization using 2,2-azobisisobutyronitrile (AIBN) as a initiator, polyvinylpyrrolidone (PVP) as a stabilizer and styrene as a monomer. PS spheres were used as the templates, then, polydopamine coatings were formed on their surface through the self-polymerization of dopamine, and ultimately obtained the PS/PDA composite spheres. Tetraethoxysilane (TEOS) was used as precursor solution, making use of the functional groups on the surface of the PDA, the raspberry-like PS/SiO2 composite spheres were prepared by biomimetic silicification. We have presented the formation mechanism of the raspberry-like PS/SiO2 composite spheres after analysizing the composition and structure of those composite spheres, and further studied the superhydrophobic and superoleophilic film constructed by the raspberry-like PS/SiO2 composite spheres.(3) Similarly, the PS/PDA composite spheres were used as templates and [Ag(NH3)2]+ ions were used as precursor solution. The [Ag(NH3)2]+ ions were absorbed onto the surfaces of the PS/PDA composite spheres by the active catechol and amine groups of the polydopamine coatings. Meanwhile, these adsorbed [Ag(NH3)2]+ ions were in situ reduced into metallic silver nanoparticles on the surface of PS/PDA composite spheres and finally obtained the PS/Ag composite spheres. As a new type of antibacterial materials, the antibacterial properties of PS/Ag composite spheres against the escherichia coli and staphylococcus aureus and the biocompatibility for human embryonic kidney cells (HEK239T) have been researched.(4) The monodisperse PDA spheres were synthesized by the self-polymerization of dopamine in an alkaline ethanol-water medium. The obtained PDA spheres were used as templates, and the biomimetic mineralization was carried out in simulated body fluid (SBF) to form hydroxyapatite (HAP) layers on the PDA spheres. The obtained PDA/HAP organic-inorganic composite material were analyzed by TEM, SEM, XRD, TGA.