Synthesis And Properties Of Inorganic/organic Hybrid Janus Composites With New Morphology

Because Janus composites have asymmetrical morphologies and compositions,a wide range of applications on emulsification,catalysis,self-propelled motor,biosensor,probe,interfacial compatibilization,etc.has been investigated.Recently,several strategies have been developed for preparation of Janus composites with various morphologies,such as sphere,rod,cage,snowman-like,raspberry-like,etc.In this dissertation,three kinds of inorganic/organic hybrid Janus composites with different morphologies were prepared,and their formation mechanism,performances and applications were studies.The detail contents are as below:1.Inorganic/organic hybrid Janus composite with three different unites was prepared via on-site polymerization and growth at the interface of oil and water.Snowman-like inorganic-crosslinked?or linear?polymer hybrid Janus composites are modified with PEO group to improve their amphipathicity,and then served as solid surfactants to emulsify deionized water and monomer?s?contained oil phase to form a water in oil emulsion.The polymerization was initiated by oil-or water-soluble initiator,and then Janus composite with three different unites was prepared at the interface of oil and water.Concretely,?1?snowman-like PEO-SiO₂/PDVB composites are served as solid surfactants to emulsify deionized water and hexane which containing St as monomer and AIBN as initiator to form the emulsion of water in oil.St was polymerized in PDVB of the snowman-like PEO/SiO₂-PDVB composites by elevating temperature,and then the PS phase was separated from the PDVB.The PEO-SiO₂/PDVB/PS composites with the A-B-C structure wereare obtained.?2?Snowman-like PEO-SiO₂/PS composites are served as solid surfactants to emulsify deionized water and n-alkane which containing VBC and DVB as monmer to form water in oil emulsion.Redox system was added under room temperature to initiate polymerization of VBC and DVB at the interface of oil and water.The PEO-SiO₂/PVBC/PS composites with the A-C-B structure were obtained by phase separation between PVBC and PS.The A-C-B type PEO-SiO₂/PVBC/PS composites with various morphologies could be obtained via modifing the total concentration of the monors,the volume ratio of different monomers and the composition of oil phase,etc..2.Preparation of single-molecular-thickness Janus nanosheets based on Schiff-base peeling.The magnetic Fe₃O₄ microspheres were covered with a thin SiO₂ layer via a solvothermal sol-gel process,which was denoted as Fe₃O₄@SiO₂ microsphere.Amino groups were decoporated on external surface of Fe₃O₄@SiO₂-NH₂ microsphereswhich were served as template in following steps,by modifying the Fe₃O₄@SiO₂ microspheres with3-Aminopropyltrimethoxysilane?APTMS?viasol-gelprocess.Triethoxysilybutyraldehyde was introduced to cover on the templating microsphere via Schiff-base reaction between amino and aldehyde groups to form imine bond,while the single layer SiO₂ was obtained via sol-gel process.Under acidic condition,the imine bonds were cleaved into amino groups and aldehyde groups,and the single-molecular-thickness silica Janus nanosheets,which possesses one side terminated by hydroxyl groups,and the other side terminated with butyl-aldehyde groups,was removed from the template microsphere with the assist of ultrasonic treatment.As to the Janus nanosheets,their 0.93 nm thickness,and great different surface wettability between the two sides indicating that they are flexible and amphiphilic,which was verified by employing them as solid surfacants to emulisify the immiscible oil and water to form stable emulsion.In addition,recyclable catelyst was fabricated by grafting chitosan capped Fe₃O₄ NPs and ionic liquid with the phosphotungstic acid as counter anion onto different sides of the Janus nanosheets,respectively,as the magnetic responsive chitosan capped Fe₃O₄ NPs could label Janus nanosheets,while phosphotungstic acid is able of catalyzing esterization reaction between oil acid and methyl alcohol.After esterization reaction,the Janus nanosheets could be precipited and separated from the solution.The yield of esterization reaction is up to c.a.80%,and no change in catalysis performance of the modified Janus nanosheets was observed after recycled the catalyst four times.3.Preparation of size-manipulable amphiphilic organic/inorganic hybrid Janus nanodiscs with magnetic responsiveness via selective protecting at interface.Ag⁺,which adsorbed on the surface of Fe₃O₄@SiO₂ microspheres,was in situ reduced to Ag nanoparticles?NPs?,and the n-octyltrimethoxysilane was grafted onto unprotected surface of silica,to obtain magnetic microsphere decorated by the Ag NPs and n-octyl groups.Ag NPs were etched off by HNO₃ and benzaldehyde groups were incorporated onto the same position via Sol-Gel process while the other part of silica surface was protected by n-octyl groups,and then benzaldehyde and n-octyl co-decorated magnetic silicatemplatingmicrosphereswereobtained.Afterwards,3-Aminopropyltrimethoxysilane was connected to benzaldehyde groups functionalized surface with imine bonds through Schiff-base reaction between amino groups and aldehyde groups,and then formed silica thin layer via Sol-Gel process.The imine groups were cleaved under acidic condition and the silica Janus nanodiscs with amino groups and hydroxyl groups on their different sides were obtained.The diameter of the Janus nanodiscs was controllable by tuning the reaction time of preparing Ag NPs and the thickness was uniform in 0.7 nm.Fe₃O₄ NPs and PEO groups were introduced to external surface of the as-formed Janus nanodiscs before exfoliation.In this case,the hydroxyl groups terminated side of Janus nanodiscs was modified with Fe₃O₄ NPs and PEO groups,while the amino groups on the other side were still preserved.Benzaldehyde was introduced onto the amino group side via imine bond.Redox the imine bond,the hydrophiphilic Janus nanodiscs with magnetic responsive were obtained,the thickness is2.5 nm and their diameter is uniform.Consider the Janus Nanodiscs as solid emulsifiers to emulisify the immiscible oil and water,the stable emulsion was got.In the external magnet field,the emulsion was demulsification,the oil and water could be separated,meanwhile,the Janus nanodisc could be collected.