【作者】 孔立智；

【导师】 潘才元；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2008， 博士

【摘要】 超支化聚合物是一类重要的非线形聚合物,具有传统线形聚合物所没有的低粘度、高流变性、良好的溶解性及大量末端官能团等一系列独特的物理和化学特性,在医药载体、非线性光学、能量存储和传递、电子器件、传感器、纳米材料、催化剂等诸多领域获得广泛应用。因此,这一领域引起了高分子科学家极大的研究兴趣,各种新型的超支化聚合物不断被合成出来。超支化聚合物的合成方法可以分为三大类:（1）多官能团单体的逐步聚合;（2）自缩合乙烯基聚合和（3）自缩合开环聚合。树枝状聚合物是一类具有完美支化结构的聚合物,与超支化聚合物相比,它们具有更加优良的性能,但缺点是合成的难度和成本太高。除了传统的树枝状聚合物外,近十年来,一种以聚合物链为结构单元的新型的树枝状聚合物也引起了高分子科学界的关注,它们具有独特的物理和化学性质,在药物载体和催化剂等方面有潜在的应用前景。树枝状-线形嵌段共聚物是另外一类包含树枝状聚合物结构单元的聚合物类型,这种复合结构结合了嵌段和树枝状聚合物的优点,表现出独特的熔融和溶液性质,在理论研究和实际应用方面都具有重要的研究价值。据此,本论文针对以下几个问题进行研究,并取得初步成果:1.为了解决A₃+B₃体系超支化聚合过程中的凝胶化问题,我们针对一种非等活性A₃+B₃单体聚合体系,三羟甲基丙烷三丙烯酸酯（A₃）和1-（2-氨乙基）哌嗪（B₃）的迈克尔加成反应进行了研究,用¹³C核磁谱原位跟踪反应过程,研究聚合反应机理。结果表明在两种单体比例为1/2或2/1时聚合反应不会产生凝胶,聚合过程按照先生成AB₂或AB₄型中间体,然后继续聚合得到超支化聚酯胺的反应路线进行。由于反应生成的仲胺在低温下不能继续反应,两种单体在-15℃可以按1/1的投料比反应,此时1-（2-氨乙基）哌嗪相当于B₂单体。另外,我们用DSC测试了得到超支化聚合物的玻璃化转变温度（T_g）,不同单体投料比得到的聚合物中三种胺的比例不同,是影响聚合物T_g最主要的因素。2.为了利用甲基丙烯酸缩水甘油酯（GMA）制备超支化聚合物,我们把Cp₂Ti（Ⅲ）Cl催化环氧开环引发自由基聚合和自缩合乙烯基聚合（SCVP）结合起来,同时用Cu（Ⅱ）X₂（X=Br,Cl）稳定自由基,控制聚合反应,研究了GMA的均聚及GMA与苯乙烯共聚的结果。单体转化率达到约60%以前,体系中没有凝胶产生,在此之后会逐渐生成部分凝胶。聚合物分子量快速增长,GPC显示多重峰,表明仍然存在偶合终止等副反应。我们通过¹H NMR谱和水解实验验证了聚合物的支化结构,支化度与Cp₂TiCl/GMA,GMA/St和聚合时间等条件有关。另外,我们用超支化PGMA作为大分子引发剂引发苯乙烯的原子转移自由基聚合（ATRP）,得到以超支化PGMA为核,聚苯乙烯为臂的超支化星形聚合物。最后,我们还研究了这些超支化聚合物用羧酸和胺类化合物改性的情况。3.为了利用点击化学合成“HyperMacs”结构的聚合物,我们通过两种途径分别合成了带有一个炔基和两个叠氮基的AB₂型PSt大分子单体以及带有两个炔基和一个叠氮基的A₂B型PSt大分子单体。这两种大分子单体都可以通过点击化学反应聚合,得到带有不同末端基团的超支化聚合物。聚合物的结构用核磁共振氢谱和GPC进行表征,GPC曲线为宽分布的多重峰,分子量分布随反应时间增加而降低,在60℃反应60小时以上,聚合度可以达到15以上。4.为了利用含有可降解链段的树枝状聚合物（dendrimer-like polymer）制备纳米空心球,我们结合ATRP和开环反应合成了两种苯乙烯和L-丙交酯的三代树枝状共聚物C（PSt（PLLA（PSt-PNAS）₂）₂）₃和C（PSt（PLLA（PSt-PNAS）₂）₂）₄。在合成第二代和第三代时,分别用二乙醇胺和2,2-二异溴丁酸甲酯基丙酰氯（BMBIBPC）作为分叉试剂,得到的聚合物用核磁共振氢谱和GPC进行表征。树枝状共聚物最外层PSt-PNAS链段利用乙二胺和NAS活性酯的取代反应交联,同时,中间的聚丙交酯段被降解,得到纳米空心球,用SEM和DLS进行观测和表征。5.为了得到两亲性哑铃形聚合物,我们合成了含有线形聚苯乙烯和树枝状聚酰胺胺的ABA型三嵌段共聚物。首先用对二溴苄作为引发剂通过ATRP得到分子量为13000的线形聚苯乙烯,然后两个末端溴用哌嗪（PZ）的一个亚胺基取代,再和过量的1,3,5-三丙酰氧基-六氢1,3,5-三嗪（TT）进行迈克尔加成反应,得到第一代（G1）三嵌段共聚物。随后,聚合物链末端反复用过量的哌嗪和TT进行迈克尔加成反应,使树枝状聚酰胺胺嵌段不断增长,得到G1.5到G4的嵌段共聚物。聚合物的结构用核磁共振氢谱和GPC进行了表征。不同代数的聚合物T_g受末端官能团的影响,具有PZ末端的聚合物由于氢键作用T_g较高。更多还原

【Abstract】 Hyperbranched polymer is an important nonlinear polymer. They have many novel physical and chemical properties, such as low viscosity, high fluidity, good solubility and a large number of terminal groups, and are broadly applied in medicine carriers, nonlinear optics, nanometer materials and catalysis. Therefore, they have attracted polymer scientists’ considerable attention. Various novel hyperbranched polymers have been synthesized successfully. Generally, there are three main synthetic approaches of hyperbranched polymers: （1） step-growth polycondensation of multifunctional groups monomers; （2） self-condensing vinyl （co）polymerization （SCV（C）P） and （3） self-condensing ring opening polymerization （SCROP）.Dendrimers are structurally perfectly branched macromolecules. They have better qualities than hyperbranched polymers, but are more difficult to be synthesized. In the past decade, a novel type of molecular architecture, named dendrimer-like polymer, has been synthesized and studied by polymer scientists, in which polymer chains are used as structural units of dendrimer. They have potential applications, such as in drug delivery and catalysis, due to their unique physical and chemical properties. Dendritic-linear block copolymers are also a type of structurally novel polymers, which have a flexible linear chain and one or two semirigid dendritic blocks. The copolymers have many unique melt and solution properties, their basic theory and practical applications have been studied.All these facts are the origin and impetus of this thesis. The main results obtained in this thesis are as follows:1. To solve the problem of gelation in A3+B3 type hyperbranched polymerization systems, hyperbranched poly（ester amine）s were synthesized by Michael addition polymerization of trimethylol propane triacrylate （A₃） and 1-（2-aminoethyl） piperazine （B3）. The mechanisms of the polymerizations were investigated by using ¹³C NMR to in situ monitor the polymerization process. When the feed ratios of TMPTA and AEPZ are 1/2 or 2/1, gelation didn’t occur. All of the polymers are considered forming by polymerization of AB₂ or AB₄ intermediates. Due to low reactivity of 2°amines （formed） at -15℃, TMPTA and AEPZ can be reacted on 1/1 feed ratio. Glass transition temperatures of the obtained hyperbranched polymers were characterized by DSC measurements, and the proportions of three kinds of amine in the polymers are main influencing factor on T_g of the polymers.2. To synthesize hyperbranched polymer using glycidyl methacrylate（GMA）, we studied the homopolymerization of GMA and the copolymerization of GMA and St by combining Cp₂Ti（III）Cl catalyzed the epoxide radical ring opening and self-condensing vinyl polymerization（SCVP）, and using Cu（II）X₂ （X = Br or Cl） to control the polymerization. Before the conversion of monomers reached 60%, no gel was generated. The GPC traces show multi-peaks and rapid increasing of molecular weights of the polymers. It indicates that coupling termination may exist. We confirmed the branching structure of the polymers by ¹H NMR spectra and hydrolysis test. The degrees of branching （DBs） of the polymers were decided by the feed ratios of Cp₂TiCl/GMA and GMA/St and polymerization time. The hyperbranched star （hyperstar） polymers with HPGMA as cores and PSt as arms were synthesized by atom transfer radical polymerization of St using HPGMA as macroinitiator. At last we studied the modifications of the hyperbranched polymers with various acids and amines.3. To synthesize "HyperMacs" of PSt using click chemistry method, we synthesized AB₂ type of PSt macromonomers with a propargyl group and two azide groups and A₂B type of PSt macromonomers with two propargyl groups and an azide group, respectively. The two macromonomers were polymerized by click reaction, and the obtained hyperbranched polymers were characterized by GPC and ¹H NMR. GPC curves show multi-peaks and broad distributions of molecular weights. M_W/M_ns gradually decrease with proceeding of the reactions. After 60 h polymerization at 60°C, the degrees of polymerization （DPs） are over 15.4. To prepare nanometer hollow sphere using dendrimer-like copolymer containing degradable polymer chains, we synthesized the three generations dendrimer-like copolymers C（PSt（PLLA（PSt-PNAS）₂）₂）₃ and C（PSt（PLLA（PSt-PNAS）₂）₂）₄ by combination of ATRP and ROP. Diethanol amine and 2,2-bis（methylene-2-bromoisobutyrate） propionyl chloride （BMBIBPC） were used as divergent reagents respectively before preparations of the second and the third generations. The resultant polymers were characterized by GPC and ¹H NMR. Then the outermost PSt-PNAS in the dendrimer-like copolymers was cross-linked via substitution reaction of NAS with ethylene diamine, and at the same time, the PLLA segments in the second generation were decomposed in dilute THF or CHCl₃ solution, forming hollow particles. The morphologies formed were characterized by SEM and DLS methods, and spherical particles with various sizes were observed.5. To obtain a amphiphilic dumbbell-shaped copolymer, we successfully synthesized dendritic-linear-dendritic triblock copolymers composed of linear polystyrene （PSt） and poly（amido amine） dendrons. Two bromines-terminated PSt with M_n=13,000 was prepared by atom transfer radical polymerization （ATRP） usingα,α’-dibromo-p-xylene as initiator. Then the terminal bromines at both ends of PSt chains were replaced by one imine group of piperazine （PZ）, and further Michael addition reaction of terminal PZ with excess 1,3,5-triacryloylhexahydro-1,3,5-triazine （TT） produced the first generation （G₁） of the triblock copolymer. Continuous growth of dendrons from G1.5 to G4 at the both ends of PSt chains was carried out by the iterative Michael addition reactions with excess PZ and following TT. Structures of the triblock polymers were characterized by GPC and ¹H NMR spectra. Thermal phase transitions of the polymers were studied by DSC measurements. The triblock copolymers with terminal PZ groups have higher T_gs due to hydrogen bonding interaction.更多还原