【作者】 程建丽；

【导师】 何军坡；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2009， 博士

【摘要】 碳纳米管在电子、光学、聚合物共混材料方面有其独特的性能,是科学界研究的热点。而纳米级的金刚石粉同样具有金刚石优良的物理和化学特性,而且其应用范围更广,纳米金刚石的制造,特别是应用,是近年来各国科学家的热门研究课题。然而它们都在溶剂中难于分散,极大地制约了其应用,因此有必要对其表面进行功能化,提高分散性和加工性能。活性自由基聚合埘聚合物的结构可控性方面有其独特的特点,在聚合物材料设计方面有着广泛的运用。其中RAFT聚合单体适用性广,反应条件温和,不存在原子转移自由基聚合中去除残余离子的问题。本文旨在采用RAFT方法合成结构可控的官能化嵌段共聚物,探讨以活性自由基聚合技术功能化碳纳米管、纳米金刚石的方法,以及聚合物修饰后的纳米材料的溶液性质。主要包括以下内容:(1)首先以偶氮二异丁腈为引发剂,二硫代苯甲酸异丙苯酯为链转移剂研究了功能性单体N,N-dimethylaminoethyl methacrylate(DMAEMA),poly(ethyleneglycol)methyl ether methacrylate(PEGMA),t-butyl methacrylate(t-BMA),2-hydroxyl ethyl methacrylate(HEMA),glycidyl methacrylate(GMA),methylmethacrylate(MMA),styrene(st)的RAFT聚合,聚合呈活性特征,得到了结构可控的多分散指数低于1.35的官能化嵌段聚合物。合成了中间嵌段带活性官能团的嵌段聚合物PtBMA-b-PGMA-b-PS,PtBMA-b-PHEMA-b-PDMAEMA,PMMA-b-PGMA-b-P(PEGMA)。利用合成的嵌段共聚物PtBMA-b-PGMA-b-PS中活性环氧基团同胺基取代的金刚烷反应,合成了嵌段中含金刚烷单元的三嵌段聚合物。(2)利用嵌段共聚物(PtBMA-b-PGMA-b-PS)的活性环氧基团与羧化的纳米金刚石的羧基反应,通过“center-Iinking”的方法得到了“V型”嵌段聚合物修饰的纳米金刚石PtBMA-g-ND-g-PS。该接枝物中聚甲基丙烯酸特丁酯链段的特丁基在三氟乙酸存在下水解,得到了两亲性聚合物聚苯乙烯PS和聚甲基丙烯酸PMAA同时接枝的纳米金刚石PMAA-g-ND-g-PS。使用TEM、SEM和TGA表征了聚合物官能化纳米金刚石的结构形态和接枝率。这种“V型”两亲性聚合物接枝的纳米金刚石不仅能在有机溶剂和水中分散而且能在油水界面进行自组装。(3)利用链中带环氧官能团或羟基官能团的嵌段聚合物(PtBMA-b-PGMA-b-PS和PtBMA-b-PHEMA-b-PDMAEMA),分别与碳纳米管表面的羧基或酰氯反应,通过“center-linking”的方法将两种不同聚合物同时接枝到碳纳米管上,得到了“V型”聚合物修饰的碳纳米管,这种不同聚合物同时接枝上碳纳米管的结构未见报到。将其中嵌段单元的特丁基水解,就得到两亲性聚合物和两性聚电解质修饰的碳纳米管。这种两亲性聚合物和两性聚电解质接枝的碳纳米管在溶剂中的分散性能得到了很大的提高,而且对pH变化敏感,还能实现碳纳米管在油水界面的白组装。(4)原始碳纳米管由于其疏水疏油性能,在超声分散后能被置换到油水的界面,形成水包油或油包水的“Pickering”乳液。原始碳纳米管在油水界面组装后将油水分为两相,我们利用界面的接枝反应来修饰碳纳米管。在水相中添加水溶性单体和水溶性引发剂,在油相中添加油溶性单体和油溶性引发剂,然后利用两相中的原位自由基聚合法一步在碳纳米管的表面同时接枝上两种不同的高分子链,得到了两亲性聚合物修饰的碳纳米管PS-g-MWCNT-g-PAM和PS-g-MWCNT-g-PDMAEMA。通过油水界面来制备两亲性聚合接枝的碳纳米管的方法简单有效,而且接枝率高。更多还原

【Abstract】 Carbon nanotubes have been an area of intense research due to its potential utility in numerous areas,such as molecular wires and electronic,sensors,high-strength fibers,and field emission displays.Nanodiamond is a promising and valuable powder material with the remarkable properties like diamond such as superhardness,excellent chemical stability,thermal conductivity and biocompatibility.Recently years,the research on Nanodiamond is become popular.Nevertheless,the carbon nanotube and nanodiamond are not soluble in almost any solvents,which remain a severe limitation to the extensive use.So,it is very important to functionalize the carbon nanotubes and nanodiamond in order to improve their dispersibility in solvents and matrics. Reversible addition fragmentation chain transfer mediated polymerization(RAFT), one of a number of leading living radical polymerization techniques,has attracted considerable interest.It provides molecular weights predetermined by the chain transfer agent and conversion,and,more importantly,Produce polymers under mild reaction conditions.The main purpose of this work is to study the synthesis of well-defined functional polymers via the RAFT process and surface-modification of carbon nanotubes and nanodiamond with polymers resulting from living radical polymerization.This dissertation contains the following aspects:(1)Functional monomers N,N-dimethylaminoethyl methacrylate(DMAEMA), poly(ethylene glycol)methyl ether methacrylate(PEGMA),t-butyl methacrylate (t-BMA),2-hydroxyl ethyl methacrylate(HEMA),glycidyl methacrylate(GMA), methy methacrylate(MMA) and styrene(st) were polymerized by RAFT with cumyl dithiobenzoate as a chain transfer agent and AIBN as initiator.The process showed living characteristic and the functional polymers were obtained with controlled molecular weights and polymer polydispersity indices less than 1.35.Tri-block copolymers PtBMA-b-PGMA-b-PS,PMMA-b-PG MA-b-P(PEGMA), PtBMA-b-PHEMA-b-PDMAEMA containing small amount of epoxy groups or hydroxyl groups in the middle of the chains were synthesized by sequential polymerization of functional monomers using macro-chain transfer agent via RAFT process.The adamantine containing block copolymers were synthesized by reaction of amantadine with the epoxy groups of PtBMA-b-PGMA-b-PS.(2)PS and PtBMA were grafted onto nanodiamond particles by the reaction of epoxy groups in the block copolymers of PtBMA-b-PGMA-b-PS and carboxylic groups on the surface of nanodiamond.This "center-linking" process resulting in "V shaped" block polymer functionalized nanodiamond PtBMA-g-ND-g-PS.TEM,SEM, and TGA were employed to determine the structure,morphology,and the grafting quantities of the resulting products.Amphiphilic polymers grafted nanodiamond PMAA-g-ND-g-PS was prepared by subsequent hydrolysis of the tert-butyl group into carboxylic group.Those "V shaped" Amphiphilic polymers grafted nanodiamond displayed dispersibility not only in organic solvent but also in water. PMAA-g-ND-g-PS self-assembled at the interfaces of chloroform and water,or toluene and water.(3)PtBMA-b-PGMA-b-PS and PtBMA-b-PHEMA-b-PDMAEMA were synthesized via RAFT process.Those block polymers were grafted onto multi-walled carbon nanotubes by the reaction of epoxy groups or hydroxyl groups in the block copolymers with carboxylic groups or chloride on the surface of tubes.This "center-linking" process resulting in "V shaped" block polymer functionalized carbon nanotubes.Amphiphilic polymers and zwitterionic polymers grafted tubes were prepared respectively by subsequent hydrolysis of the tert-butyl group into carboxylic group.These Amphiphilic polymers and zwitterionic polymers grafted tubes displayed dispersibility not only in organic solvent but also in water and showed pH responsibility.PMAA-g-MWCNT-g-PS and PMAA-g-MWCNT-g-PDMAEMA can self assemble at the interfaces of chloroform and water,or toluene and water.(4)Pristine carbon nanotubes are insoluble in either water or oil.When mixtures of CNTs,water,and organic solvent are sheared vigorously,a macroscopic emulsion of oil droplets forms in water,with the CNTs residing at the interface between the immiscible fluids,acting as a natural "surfactant" or interphase material.Herein we present the formation of amphiphilic polymer grafted CNTs by simultaneous biphasic grafting of different polymer at a liquid/liquid emulsion interface through free radical polymerization.Interface is separated into two phases,which can be synchronously modified by free radical polymerization in the two phases with hydrophilic/lipophilic monomers.As a result,through one single step we prepared amphiphilic polymer grafted CNTs PS-g-MWCNT-g-PAM and PS-g-MWCNT-g-PDMAEMA.This approach is facile with high grafting efficiency.更多还原