| With the development of polymer and material sciences,new requirements for basic synthetic technologies,such as controllabilty,high efficiency,high selectivity etc are presented.According to these requirements,those newly developed techniques, such as controlled free radical polymerization and "click chemistry",have been poured great passion by the scientists.They provided the scientists with powerful methods to synthesize various special-structured polymers as well as various organic & inorganic materials.Smartly application of these techniques in polymer synthesis and material modification is one of the most important topics in the field of chemistry. Based on the researchs of the precursors,this dissertation described several outspread works in the synthesis of topologically structured polymers and the modification of carbon nanotubes.All these facts are the origin and impetus of this thesis.The main results obtained in this thesis are as follows:1.The ABCD 4-miktoarm star polymers based on polystyrene(PS), poly(ε-caprolactone)(PCL),poly(methyl acrylate)(PMA) and poly(ethylene oxide)(PEO) were synthesized and characterized successfully.Using the mechanism transformation strategy,PS with three different functional groups, hydroxyl,alkyne and trithiocarbonate,PS-HEPPA-SC(S)SC12H25,was synthesized by the reaction of the trithiocarbonate-terminated PS with 2-hydroxyethyl-3-(4-(prop-2-ynyloxy)phenyl)acrylate(HEPPA) in tetrahydrofuran solution.Subsequently,the ring-opening polymerization(ROP) of CL was carded out in the presence of stannous(Ⅱ) 2-ethylhexanoate and PS-HEPPA-SC(S)SC12H25,and then the PS-HEPPA(PCL)-SC(S)SC12H25 obtained was used in the reversible addition -fragmentation chain transfer(RAFT) polymerization of MA to produce the ABC 3-miktoarm star polymer, S(PS)(PCL)(PMA) carrying an alkyne group.The ABCD 4-miktoarm star polymer,S(PS)(PCL)(PMA)(PEO) was successfully prepared by click reaction of the alkyne group on the HEPPA unit with azide-terminated PEO(PEO-N3).2.Well-defined inverse star block copolymer,(PCL-PS)2-core-(PCL-PS)2 has been successfully prepared through a combination of ATRP,ROP and "Click chemistry".Different from star block copolymer,core-(PCL-PS)4 prepared using core-first method,the feasible synthetic strategy of the inverse star (PCL-PS)2-core-(PCL-PS)2 is a combination of core-first and ann-first methods. Starting from a heterofunctional initiator BMDB,ATRP of St and following "click" reaction of(N3-PS)2-core-(OH)2 with linear(CH≡CCH2)PCL -(OOCCH3) produced block copolymer(PCL-PS)2-core-(OH)2.After ROP of CL using(PCL-PS)2-core-(OH)2 as macroinitiator and successive transformation of terminal hydroxyl groups into bromine groups,ATRP of St using (PCL-PS)2-core-(PCL-Br)2 as macroinitiator yielded successively inverse star block copolymer,(PCL-PS)2-core-(PCL-PS)2.The intricate structure of the inverse star block copolymer influenced the microphase separation of PS and PCL segments,in turn,affected the crystallization of PCL.3.Found a new noncovalent method to functionalize the carbon nanotubes with polymer.Well-defined hexa-armed star poly(L-lactic acid)(PLLA) with a triphenylene core has been prepared by ring-opening polymerization of LLA.Due to the strongπ-πinteractions between the triphenylene core and multi-walled carbon nanotubes(MWNTs),the polymer was conveniently immobilized on the surface of the as-received MWNTs by a simple ultrasonic process while the intrinsic graphitic structure of the pristine MWNTs is retained.Both debundling of MWNT ropes and polymer attachment are achieved in a single step.Increasing the molecular weight of the PLLA arms or using high polarity solvent may decrease the amount of the polymers grafted onto the MWNTs.Detailed research demonstrates that the triphenylene cores were probably strongly anchored on the side walls of the nanotubes where the carbons are in well graphitic configuration.4.The preparation of exquisite hierarchical worm-like silica nanotubes by a simple sol-gel method is presented for the first time,in which poly(2-(dimethylamino)ethyl methacrylate)-grafted multi-wall carbon nanotube (MWNT-g-PDMAEMA) was used as sacrificial template.A possible formation mechanism of this interesting structure has been proposed.And the protonated 2-(dimethylamino) groups of PDMAEMA chains is believed to be responsible for the formation of the exquisite hierarchical structure of the formed nanoparticles. The hierarchical silica nanotubes have characteristic of mesoporous materials, such as large surface area,multiple pore distribution and large pore volume,and would have potential applications as catalyst or biosensors.5.Developed a novel method to functionalize the carbon anotubes with end functioned polymer brushes.Firstly,we synthesized crown ether capped polystyrene by ATRP method using an initiator carrying the crown ether group; after the terminal bromine had been transformed into azide groups,theα-azide,ω-crown ether ended polymer was grafted onto the surfaces of carbon nanotubes by "click chemistry" conveniently.The as prepared CNT-PS-Crown composites were good candidates for phase transfer catalysts,carriers for metal catalysts or separation films.Nano sized silver particles have been synthesized in situ on the surfaces of the CNTs due to the host-guest interactions of siliver and crown ether groups. |
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