Synthesis, Structure And Properties Research Of Functional Materials With Multi-perfluoroalkyl Chains

Considering the long fluorocarbon chains will not hydrolyze, photolyze or biodegrade in most environmental conditions, which will be harmful to the environment. Therefore, the materials with long fluorocarbon chains have been gradually banned. In order to establish the basic theory and methods of using materials with short fluoroalkyl chains to replace materials with long fluoroalkyl chains, a series of functional materials with multi-perfluoroalkyl chains were synthesized by the reactions of hydrosilylation, click chemistry, esterification, Grignard reaction, single electron transfer in this dissertation, in which the short multi-perfluoroalkyl chains were successfully attached by the bridging groups, such as triazole, siloxyl, silyl and silsequioxane. These newly synthesized materials were never reported before. Then these materials were applied onto the silicon substrates and cotton fabrics. Afterwards, the relationship between the structure and properties of self-assembled films and treated cotton fabrics was well analyzed. In addition, the mechanism and microscopic structures of self-assembled perfluoroalkylsilane films were investigated in depth, the preparation methods of materials with low surface free energy were studied as well. Main discussions were as follows:(1) Silanes functionalized with mono- and bis-fluoroalkylated [1,2,3]-triazolesSilanes functionalized with mono- and bis-fluoroalkylated [1,2,3]-triazoles were synthesized by esterification, click chemistry and hydrosilylation reactions using sodium azide, propargyl bromide, allyl bromide, trichlorosilane and perfluoroalkyl ethanol as raw materials. The structure of synthesized compounds were confirmed by FT-IR、1H NMR、13C NMR、19F NMR and MS. Then four self-assembled perfluoroalkylsilane films on silicon wafers were fabricated by the method of liquid phase deposition. EDS and AFM measurements found that the perfluoroalkylsilane molecules gradually assembled onto the surface of silicon wafer with the extension of assembling time; the changes of surface element contents and morphology of self-assembled perfluoroalkylsilanes films were analyzed by XPS and AFM, and results showed that annealing process and extension of assembling time can improve contact angles, decrease surface free energy and adhesive force of self-assembled perfluoroalkylsilane films.(2) Multi-perfluoroalkylsiloxyl polymethacrylatesMulti-perfluoroalkylsiloxyl methacrylate monomers were synthesized by hydrosilylation and Grignard reaction, and multi-perfluoroalkylsiloxyl polymethacrylates(namely PMFSMA, PBFSMA and PTFSMA) were obtain by the emulsion polymerization, then they were applied onto the cotton fabrics. The properties of the fluorinated polyacrylates and treated cotton fabrics were analyzed, and the results were as follows: the emulsion stability decreased with the increase of fluorine content, and there were smaller particles as well as bigger ones existing in the elmusion with high fluorine content; polymer with high fluorine content decomposed faster at initial stage due to the presence of oligomers, and the amount of residue increased with the increase of fluorine content; EDS graphs showed that perfluoroalkyl chains have migrated to the film-air interface during annealing process; incorporation of more fluoroalkyl segments into the polymer and annealing process could significantly decrease the surface free energy as low as 13.7 mN/m; water contact angles of the treated cotton fabrics increased with the increasing fluorine content, and water contact angles of PTFSMA treated cotton fabrics have larger angles than other samples at the same fluorine content(154.1o).(3) Multi-perfluoroalkylsilyl polymethacrylatesUsing perfluorohexyl ethyl bromide as raw materials, multi-perfluoroalkylsilyl methacrylate monomers were synthesized by hydrosilylation and Grignard reaction, and multi-perfluoroalkylsilyl polymethacrylates(namely PMFSA, PBFSA and PTFSA) were obtain by emulsion polymerization, then they were applied onto the cotton fabrics. The properties of the fluorinated polyacrylates and treated cotton fabrics were analyzed, and the results were as follows: shortening the length of siloxane chains, incorporation of more fluoroalkyl segments into the polymer together with annealing process could further reduce the surface free energy as low as 12.04 mN/m, which was decreased by 12.1 % compared to the fluorinated polyacrylates prepared in the third chapter of this dissertation; the surface of PTFSA with annealing process exhibited an obvious roughness which was resulted from the segregation of perfluoroalkyl chains on the air-polymer interface, driven by the low surface energy of fluorinated segments and unfavorable interactions between perfluoroalkyl chains and non-fluorinated acrylates; EDS and XPS measurements confirmed the enrichment of fluorine on the outmost layer of the fluorinated polyacrylate film and treated cotton fabric; water contact angles of treated cotton fabrics increased with the increasing fluorine content, and even after 15 washes, the treated cotton fabrics still showed high water contact angles.(4) Multi-perfluoroalkylsilsesquioxane polymethacrylatesVinyl silsesquioxane was synthesized using vinyl trichlorosilanes as the raw material, and seven perfluorobutyl chains were attached to the vinyl silsesquioxane by the single electron transfer reaction, then the multi-perfluoroalkylsilsesquioxane methacrylate monomer was successfully synthesized with triethylamine as acid binding agent, and multi-perfluoroalkylsilsesquioxane polymethacrylates were obtain by emulsion polymerization. The fluorinated polyacrylates have denser perfluoroalkyl side-chains, which possessed extremely low surface free energy as 9.75 mN/m. In addition, the thermal stability of polyacrylates was improved because of the introduction of fluorinated silsesquioxane.Results showed that the bridging groups had a great influence on the surface properties of fluorinated materials. The rigid triazole brigding group could promote the ordered arrangement of terminal perfluoroalkyl groups, which benifited the surface shielding effectiveness of short perfluoroalkyl chains; the flexible siloxyl bridging groups could improve the migration and separation of short perfluoroalkyl chains, which brought in low surface free energy under high temperature treatment; the silsesquioxane bridging groups could introduce more short perfluoroalkyl groups, which resulted in densely packed short perfluoroalkyl groups and could be used to prepare fluorinated materials with excellent performance. The research results conform to the trend of green and environmentally friendly materials, and these results could establish the theoretical basis for the designing and preparation of materials with short fluoroalkyl chains, which may have the same performance as those materials with longer fluoroalkyl chains.