【作者】 张永文；

【导师】 徐僖； 颜德岳；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 博士

【摘要】 超支化聚合物是一类具有准球形结构的高度支化大分子,在其不规则的分子结构中含有大量内部空穴和末端官能团。由于超支化聚合物独特的结构和性能特点,目前它已成为高分子领域的研究热点。经过近20年的发展和探索,人们在超支化聚合物的合成、结构表征、功能化改性等方面已经取得了重要进展,尤其是超支化聚合物的合成方法已经趋于全面和成熟,这为超支化聚合物的应用开发奠定了坚实的基础。但是,在超支化聚合物的研究中还有许多问题亟待解决,如基础理论的完善、未知性能的挖掘、新颖现象的解释、应用领域的拓展等等。本文在综述前人有关超支化聚合物工作的基础上,在超支化聚合物的功能化方面做了一些新的探索和研究。基于本课题组有关官能团非等活性单体对的合成策略,设计合成了一类功能性的超支化聚酰胺胺,并且通过不同的改性手段得到了更多具有实际应用前景的功能材料。研究工作中,制备得到了超支化聚合物凝胶因子;将超支化聚酰胺胺用于复合自组装,并通过化学交联制备得到了结构稳定的功能性聚合物空心微球;将超支化聚合物同时作为稳定剂和还原剂,得到了具有高效抗菌性能的胶体金属纳米粒子水分散液;通过质子化、引入阴离子配体和交联改性,得到了具备一定强度的多功能聚合物膜材料,其表现出有趣的质子传导特性和独特的客体分子吸附性能。具体研究内容和主要结论概括如下:1.超支化聚酰胺胺凝胶因子的合成及物理凝胶的制备合成了一类新型的超支化聚合物凝胶因子,即由N,N-亚甲基双丙烯酰胺和1-(2-胺乙基)哌嗪通过迈克尔加成聚合得到的端氨基超支化聚酰胺胺。聚合过程中,1-(2-胺乙基)哌嗪中各类胺的非等活性是形成支化结构的关键因素,所得超支化聚合物的支化度借助二维核磁进行了系统表征。该超支化聚合物可在多种有机溶剂中组装形成稳定的物理凝胶,包括N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)、二甲亚砜(DMSO)、N-甲基吡咯烷酮(NMP)和吡啶等,其对DMF的凝胶化能力尤为强烈,临界凝胶浓度约为2.5 mg/mL。所形成的物理凝胶具有温度响应性,即在加热的条件下形成聚合物透明溶液,冷却形成非流动的固态凝胶,此过程可逆。冷冻透射电镜测试结果表明,所得物理凝胶的微结构由开放式的连续的聚合物网络构成。进一步研究表明,超支化聚合物分子之间的相互氢键作用是形成物理凝胶的驱动力。在溶液状态,聚合物分子间氢键较弱,随着温度降低,分子间氢键加强,导致分子相互插入、聚集,进而组装形成连续的聚合物网络,得到不可流动的物理凝胶,HPMA分子中的酰胺单元和各类胺单元都参与了氢键的形成。此外,所得凝胶还体现出了典型的物理凝胶特征动力学行为。2.超支化聚酰胺胺与聚丙烯酸的复合自组装及交联空心微球的制备采用超支化聚酰胺胺/线性聚丙烯酸聚合物对(h-PAMAM/l-PAA),在水溶液中进行复合自组装并采用壳层化学交联的手段,制备得到了一种新型的聚合物空心微球。通过调控组装溶液的pH值,可以得到形貌丰富的复合自组装体,包括纳米级的实心粒子和纳米至微米级的囊泡。当pH < 2.1时,形成了由无规堆积的l-PAA内核和质子化的h-PAMAM外层组成的实心球形粒子;当pH > 7.5时,形成了由无规堆积的h-PAMAM内核和溶剂化的l-PAA外层组成的实心球形粒子;而当组装溶液的pH在2.1 - 7.3范围内,复合组装体由实心粒子转变成囊泡中空聚集体,而且在pH = 4.6附近,囊泡内外壁结构发生了翻转。研究中采用光学显微镜、分光光度计、TEM以及zeta电位等测试手段,探索了复合体在水中的自组装行为及组装机理,其自组装的驱动力为疏水-亲水平衡作用以及h-PAMAM中各类胺单元与l-PAA中羧基的特殊相互作用。进一步采用交联剂戊二醛交联,可将所得囊泡的空心结构固定下来,得到稳定的PAMAM空心微球,该聚合物空心微球能同时作为模板剂和还原剂,在水溶液中与金属前驱体反应,制备得到负载有银、金或钯等贵重金属纳米粒子的杂化微球,其中金、银和钯的含量分别达到15.2 wt%、12.3 wt%和8.0 wt%,这类杂化微球在金属催化领域具有潜在的应用价值。在制备复合囊泡、交联空心微球和负载贵重金属纳米粒子的过程中,无需复杂的物理/化学过程,简便高效。3.超支化聚酰胺胺同时作为稳定剂和还原剂制备具有优异抗菌性能的胶体金属纳米粒子采用超支化聚合物(即端氨基超支化聚酰胺胺HPAMAM-NH2)同时作为稳定剂和还原剂,通过简便、有效、绿色的方法,制备得到了具有优异抗菌性能的胶体银纳米粒子,采用FTIR、UV-vis、TEM、EDS和XRD等表征手段证实了银纳米粒子的生成。本方法制备的银纳米粒子水分散性好且粒径小,平均粒径为4-15 nm,并且,通过改变聚合物的添加量(即N/Ag加料摩尔比)便可有效控制其粒径大小。进一步研究发现,聚合物中的超支化结构、酰胺单元、哌嗪环和叔胺单元在还原和稳定过程中起到了协同作用,它们的共存使得该超支化聚合物具备了优良的还原能力和稳定化作用。所得HPAMAM-NH2/Ag纳米复合物能够有效抑制多种革氏阳性和革氏阴性细菌的生长和繁殖,这些细菌包括Staphylococcus aureus、Bacillus subtilis、Escherichia coli和Klebsiella mobilis等,当银的浓度仅为2.7μg/mL时,其抑菌率能高达95%以上。所得金属纳米粒子的粒径小,从而具有较大的比表面积,显现出优异的抗菌效果;同时由于质子化超支化聚酰胺胺具有阳离子特性,其对抗菌效果也起到一定的协同作用。该方法还能进一步拓展,如采用端二甲胺基的超支化聚酰胺胺HPAMAM-N(CH3)2亦能制备稳定的胶体银或金纳米粒子,它们对细菌和真菌都具有高效的抗菌性能。所得纳米粒子的粒径可在1.0-8.5 nm范围内可调,当银的含量为2.0μg/mL或金的浓度为2.8μg/mL时,所得纳米复合物的抑菌率均能达到98%以上。4.通过改性超支化聚酰胺胺制备具有良好质子传导性的交联聚合物电解质膜采用质子化、引入三氟甲磺酸根(Tf2N-)和末端自交联的方法,对合成所得的端双键超支化聚酰胺胺进行改性,成功制备了一系列结构新颖的交联聚合物电解质膜。在聚合物交联网络的支化微区中,存在不同含量的质子产生位点(即质子化叔胺)和疏水性Tf2N-的自发聚集区。所得聚合物电解质膜具备良好的机械强度和热稳定性,吸水率为8.4-24.5%。在30-80℃的温度范围内,所得聚合物电解质膜的质子传导率在10-5-10-2 S/cm数量级范围,并且其质子传导率随质子化率的增加而提高。AFM结果表明,聚合物膜中亲水的质子产生位点和疏水的Tf2N-聚集区产生了微相分离,从而形成了局部连续的亲水簇,它们能够充当质子传输通道的作用,有利于产生良好的质子传导性。这种聚合物电解质膜在聚合物电解质燃料电池(PEFCs)和其它电化学领域有着潜在的应用。5.基于超支化聚酰胺胺改性制备具有独特吸附性能的交联聚合物膜主体材料通过对合成端双键超支化聚酰胺胺进行类似的改性,制备得到了具有一定机械强度的聚合物膜主体材料c-HP,它对客体染料分子和金属离子表现出独特的吸附性能。一方面,聚合物膜c-HP能够高效地吸附不同种类的水溶性染料。在每升染料溶液中,每克聚合物膜对染料的吸附能力能达到0.3 g/L,染料溶液的脱色率达98%以上。更重要的是吸附了染料的聚合物膜还可再生和重复使用,且可保持对染料的吸附效率不变。这种特性可归结于聚合物膜的特殊分子结构,如聚合物膜中的三维交联网络、支化微结构中的大量空穴、亲水性质子化叔胺单元和疏水性Tf2N-聚集区。另一方面,经碱处理后的聚合物膜c-HP不仅能从水溶液中吸附贵重金属离子,并可将其原位还原生成金属单质,得到含有银、金、钯或铂纳米粒子的聚合物杂化膜,膜中的纳米粒子分布均匀,尺寸小(几个纳米至几十个纳米),此吸附过程中,聚合物膜同时起到了模板剂和还原剂的作用。该聚合物膜主体材料的应用过程中,仅采用简便的水溶液浸泡法,因而在废水处理与金属催化等领域具有潜在的应用优势。总而言之,本论文中合成超支化聚酰胺胺的简便方法为超支化聚合物的规模化生产提供了可行方案,而且,基于该超支化聚合物改性制备不同种类功能性材料的探索与开发,为超支化聚合物的学术研究和实际应用提供了重要信息。更多还原

【Abstract】 Hyperbranched polymers are a novel kind of three dimensional torispherical irregular macromolecules possessing highly branched architectures, many inner cavities and a large amount of terminal functional groups. Due to their unique molecular structures and properties, hyperbranched polymers have become the hot topics in many R&D fields. Up to date, the great progress has been made in the synthesis, characterization, modification, and application of hyperbranched polymers. Especially, various synthesis methodologies have been developed during the past two decades, which provide the promising chance for their applications. However, many problems still need to be resolved, such as how to perfect the theories, how to explore the unknown features, how to explain new phenomena and spread the application fields. In this dissertation, the previous studies of hyperbranched polymers are summarized firstly, including their synthesis, properties and applications. Based on them, some creative investigations are conducted in the synthesis and modification of hyperbranched polymers to obtain various functional materials. A novel kind of functional hyperbranched polyamidoamins are designed and synthesized via the A2+BB’2 strategy. Several interesting functional materials are further generated by the modification of the resulting hyperbranched polymers. In our research works, (1) the first hyperbranched polymer gelator, i.e., the amine-terminated hyperbranched polyamidoamine is investigated systematically. (2) The hyperbranched polyamidoamine is successfully used to form the hollow spheres (i.e., vesicles) via complex self-assembly, and the hollow spheres are further stabilized by chemical cross-linking. (3) Besides, the hyperbranched polyamidoamines are served as both reductants and stabilizers to prepare the stable colloid metal nanoparticles with highly antimicrobial activities. (4) In addition, the multifunctional polymer films with enough mechanical strength are prepared from modification of the hyperbranched polyamidoamines. The films show promising proton-conductive behavior and effective binding abilities to various guest molecules. The details and key conclusions are described as follows: 1. Synthesis of the Amino-terminated Hyperbranched Polyamidoamine Gelator and the Formation of Physical GelA novel kind of hyperbranched polymer gelator, i.e., the amino-terminated hyperbranched polyamidoamine, is obtainted successfully. It is synthesized by the Michael addition polymerization of N,N’-methylene bisacrylamide (MBA) and 1-(2-aminoethyl)piperazine (AEPZ). The unequal reactivity of the various amines in AEPZ leads to the formation of the hyperbranched structure in the polymerization. The degree of branching (DB) is characterized with the assistance of 2D NMR. The resulting polymer can self-assemble into the thermo-reversible physical gel in DMF, DMAC, pyridine, DMSO or NMP. Its gelation ability to DMF is the strongest among them, with the critical gelation concentration (CGC) being as low as 2.5 mg/mL. The microstructure of the gel consists of continuous and open network on the nano scale revealed by cryo-TEM. It is further revealed that the driving force of the gelation is ascribed to the hydrogen bonds among amide and amine groups in the highly branched macromolecules. Besides, the gels also exhibit the typical dynamic mechanical behavior of physical gels.2. Hollow Spheres Based on Complex Self-assembly of Hyperbranched PAMAM/Linear PAA Polymer Pair and Their FunctionizationA novel kind of polymer hollow spheres are prepared successfully based on the complex self-assembly of the hyperbranched PAMAM/linear PAA (h-PAMAM/l-PAA) polymer pair in aqueous solution. By adjusting the solution pH, the assembled aggregates of nanoparticles or vesicles are formed When the pH is lower than 2.1, the assembled aggregates are nanoparticles with l-PAA as the core and the prontonated h-PAMAM as the shell. On the contrary, when the pH is upper than 7.5, the resulting nanoparticles consist of the inner h-PAMAM and outer layer of the solvated l-PAA. When the pH is in the range from 2.1 to 7.3, the aggregates become into vesicles and exhibit the typical hollow structure. Interestingly, at ca. pH 4.6, the vesicle conversion happens. The optical microscopy, UV-vis spectrometer, TEM and zeta potential are adopted to investigate the behaviour and mechanism of the complex self-assembly. The driving forces of the complex self-assembly are ascribed to hydrophilic-hydrophobic balance and the specific interactions between the carboxylic acid groups of l-PAA and various amine units of h-PAMAM. Since the self-assembled vesicles are sensitive to the environment changes, we try to use glutaric dialdyde (GDA) as a cross-linker to stabilize their hollow structures. The resulting cross-linked hollow spheres are very stable and they can be used to encapsulate various noble metallic cations and reduce them into nanoparticles in situ. In the resulting hybrid hollow spheres, the content of Au, Ag or Pd reaches 15.2 wt%, 12.3 wt%, or 8.0 wt% respectively. Such hybrid materials may be suitable for the potential applications in metal catalysis.3. Hyperbranched Polyamidoamines as Both Reducing and Stabilizing Agents to Form Colloid Metal Nanoparticles Facilely and Their Highly Antimicrobial ActivityA facile and green method is described to prepare the stable colloid silver nanoparticles in aqueous solution by utilizing the amine-terminated hyperbranched poly(amidoamine) (HPAMAM-NH2) both as stabilizer and reductant. The formation of silver nanoparticles is verified by FTIR, UV-vis, TEM, EDS and XRD measurements. The well-dispersed colloid silver nanoparticles with small particle sizes are obtained. And the average particle size can be controlled effectively from ca. 15 to 4 nm by simply adjusting the molar ratio of N/Ag in feed. The antibacterial activity of the HPAMAM-NH2/Ag nanocomposites is also investigated against Gram-positive and Gram-negative bacteria. They are able to inhibit the growth and multiplication of several kinds of bacteria efficiently, such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Klebsiella mobilis. The bacterial inhibition ratio reaches up to 95% at a low silver concentration of 2.7μg/mL. This method can also be extended to other derivative systems. Typically, a series of colloid silver or gold nanoparticles (AgNPs or AuNPs) are also successfully prepared by in situ reduction and stabilization of hyperbranched poly(amidoamine) with terminal dimethylamine groups (HPAMAM-N(CH3)2) in water, and they all exhibit highly antimicrobial activity. The particle size can be adjustable from ca. 8.5 and 1.0 nm. The bacterial inhibition ratio reaches up to ca. 98% at the low silver (or gold) content of 2.0μg/mL (or 2.8μg/mL). The resulting metal NPs with smaller particle size can provide much more effective contact surface with the bacteria, thus enhancing their antimicrobial efficiency. Besides, the cationic nature of the hyperbranched PAMAMs can also do some contribution to the antimicrobial activity. The coexistence of the amide moieties, piperazine rings and tertiary amine groups in the hyperbranched structure is important to their effective reducing and stabilizing abilities. Besides, it is note worthy that many terminal functional groups in the hyperbranched PAMAMs can be modified to fabricate series of promising antibacterial materials.4. The Polymer Electrolyte Film with Proton Conductive Properties by Modification of Hyperbranched PolyamidoamineA series of novel crosslinked polymer electrolyte membranes are successfully prepared based on the modification of a hyperbranched poly(amidoamine) with terminal vinyl groups. The membranes possess the different contents of proton-generating sites (i.e., protonated tertiary amine groups) and triflate (Tf2N-) in the crosslinked network. They show good mechanical and thermal stability. The water uptakes of them are ca. 8.4-24.5%. Their proton conductivity is in the order of ca. 10-5-10-2 S/cm from 30 to 80 oC, and it increase with improving the protonation ratio. AFM results disclose the micro-phase separation of the hydrophilic proton-generating sites and the hydrophobic domains of Tf2N- ions. The resulting locally continuous hydrophilic clusters provide proton transport channels to produce the high proton conductivity. This kind of polymer electrolyte membranes may have potential applications in PEFCs and other electrochemical fields.5. A Robust Film Generated from Hyperbranched Polyamidoamine as Host Material and Its Efficient Binding AbilitiesA functional film (named as c-HP) with enough mechanical strength is prepared by the modification of the hyperbranched polyamidoamine and it shows effective binding properties to dyes and metal cations. On the one hand, the film c-HP can encapsulate various water-soluble dyes efficiently, and it can be regenerated and used repeatedly without decreasing its binding efficiency. The effective dye encapsulation ability is attributed to its unique molecular structure, i.e., three dimensional cross-linked networks, the numerous cavities in the branched microstructure, the coexistence of the hydrophilic protonated tertiary amine groups and the hydrophobic assembly of triflate (Tf2N-). On the other hand, the base-treated film c-HP is also able to absorb silver cations (Ag+) from silver nitrate (AgNO3) aqueous solution and reduce Ag+ into Ag0 in situ, producing the hybrid films containing Ag nanoparticles. In this process, the film c-HP exhibits the self-reduction and stabilization role due to the numerous amino groups in the branched points. Furthermore, its binding properties can be extended to some other noble metals like gold (Au), palladium (Pd) and platinum (Pt). As a result, this kind of polymer film material may have promising applications in the fields of dye wastewater treatment and metal catalysis.In one word, the facile preparation of hyperbranched polyamdioamines pays the way for their large-scale production and wide applications. The modification exploring and studies on such kind of hyperbranched polymers to obtain various functional materials provide some important information for the academic researches and the applied fields.更多还原