【作者】 李伟；

【导师】 刘和文；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2016， 博士

【摘要】 超支化聚合物以及基于超支化结构而衍生出的拓扑结构在药物传输、催化和纳米技术等方面存在着广泛的用途。得益于活性聚合手段,越来越多的基于超支化分子的拓扑结构被合成出来,如星形、哑铃形、雨伞形、蠕虫状聚合物等。非球形尤其是一维聚合物纳米粒子在纳米复合物和药物传输载体领域,许多情况下比它们的竞争对手即球形聚合物粒子更具优势。但它们的合成通常比较繁琐。光驱动微型游动粒子在下一代药物传输及微型机器人器械等方面有着广泛的潜在应用。人们所希望的是,微型游动粒子的运动不仅仅是自发式的,其方向也要可控,这样才更容易实现其应用。本文所讲述的工作主要是制备基于超支化分子的衍生拓扑结构,并赋予其特殊的功能或性能。其中,第二章和第三章主要讲述的是运用两种不同的方法制备一维超支化串珠状聚合物,并表征其一维有序特性；第四章讲述的是制备螺吡喃封端的超支化聚酯,并研究其组装的微米胶束粒子的趋光性。具体是：1)采用一种比较方便简单的“一锅法”策略,即自引发性单体的自偶联同步活性聚合合成一维超支化串珠状聚合物。在这个方法中,单体为自身可以发生超支化反应的自引发性单体,链转移剂环状三硫代碳酸酯作为偶联剂,将超支化结构沿一个方向连接起来。研究了聚合机理以及偶联剂含量对聚合过程的影响。所得聚合物的粘度特性、X射线衍射峰及液晶特性均表明了其一维有序特征。2)采用两步法合成一维纳米串珠状聚合物。第一步,自引发性单体聚合合成超支化聚苯乙烯前驱体；第二步,用偶联剂硝酮将超支化前体连接起来。研究了硝酮对偶联反应的影响。所得聚合物的粘度特性、X射线衍射峰及液晶特性均表明了其一维有序特性。3)在超支化聚酯末端接枝螺吡喃基团,合成首例全有机合成的紫外光驱动的微米粒子,并且实现了光对游动粒子运动方向的控制。粒子在分散介质中受紫外光照后表现出了正向趋光性,即粒子从四面八方迎着光向强度最大的光源中心运动,运动的轨迹为直线。我们统计出光驱动下粒子的均方速率在20微米/秒,并且在加入质量分数为0.5%的氯化钠后能够增加到54微米/秒。粒子在紫外光场下表现出正向趋光性运动的原因是光照导致粒子表面与分散介质间的界面张力的不均匀分布梯度。这一发现将为设计用于药物传输、微型机器人以及自适应型光催化的微型引擎提供一种新的方法。更多还原

【Abstract】 Hyperbranched polymers and the polymer constructs based on hyperbranched blocks have applications in a variety of fields including drug delivery, catalysis and nanotechnology, etc. More and more topological structure based on hyperbranched molecules have been synthesized, such as star, dumbbell-shaped, umbrella-shaped, and worm-like polymer. Non-spherical especially the one-dimensional nanoparticles hold some advantage in many cases in the field of polymer nanocomposites and drugs delivery carrier than their counterpart, namely spherical polymer particles. But synthesis of one-dimensional nanoparticles is usually very complicated.Light-driven microswimmers hold great promise in the field of next-generation drug delivery and micro-robot device. It is desired that the movement of micron particles is not only spontaneous but the direction also controllable, so as to implement their applications.The work described in this thesis is mainly based on the preparation of topological structure derived from hyperbranched molecules, as well as the special properties or functions thereby. The second and third chapter is mainly about preparation of one-dimensional hyperbranched-linking-hyperbranched polymer beads using two different methods. The fourth chapter is about the preparation of the spiropyran terminated hyperbranched polyester, and research the phototaxis property of the colloidal particles assembled by the photochromic hyperbranched polymer. Details included as following:1) We synthesized one-dimensional hyperbranched-linking-hyperbranched beads polymers by using a convenient "one-pot" strategy, namely self-coupling concurrent living polymerization. In this method, the monomer we used was the inimer which could initiate itself to afford hyperbranched polymer. A chain transfer agent cyclic trithiocarbonate served as "hyper linker" to link hyperbranched blocks. The polymerization mechanism and the role of chain transfer agent were investigated. Viscosity characteristics, X-ray diffraction peaks and liquid crystal properties of the resulting polymer showed the one-dimensional ordered features.2) We synthesized one-dimensional hyperbranched-linking-hyperbranched beads polymers by two steps. First, polymerization of the inimer to synthesize hyperbranched polystyrene precursor. Second, making the precursor linked by the coupling agent nitrone. The effect of nitrone to the coupling reaction was studied. Viscosity characteristics, X-ray diffraction peaks and liquid crystal properties of the resulting coupled polymer showed the one-dimensional ordered features.3) We synthesized the first example of fully organic microparticles which could be driven as well as steered by light source. These particles showed a positive phototaxis when they were dispersed and irradiated by UV light, ie, particles moved from all directions to the light source center. The movement trajectory was straight line. The mean-square velocities of the photochromic suspension particles were about 20 μm·s-1, and increase to about 54 μm·s-1 with the addition of NaCl of 0.5%. The phototactic propulsion is supposed to be originated from the UV irradiation-induced interfacial tension gradient on the surface of the colloidal particles. This finding allows for the design of new micro-engines for next-generation drug delivery systems, micro-robotic devices, and self-adaptive photocatalysts, etc.更多还原