【作者】 李丽英；

【导师】 王延梅； 何卫东；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2011， 博士

【摘要】 高分子材料被广泛应用于航天、军工和民用等各个领域。活性自由基聚合以及点击反应等高分子合成技术的发展使所得到的高分子材料的性能逐渐提高。活性自由基聚合反应和点击反应不仅为合成各种特殊结构的聚合物,如接枝、星形和环形聚合物等,提供了有效的手段,也为各种无机或有机材料的改性提供了宽广的技术平台。本文在高分子合成和材料改性等方面进行了有意义的探索,具体研究内容和结果如下:1.利用单电子转移活性自由基聚合以及点击反应相结合,在高浓度下成功制备了全亲水性蝌蚪形嵌段共聚物,即线形聚(N-异丙基丙烯酰胺)-b-环状聚乙二醇(tail-PNIPAM-c-PEG)。首先通过单电子自由基聚合制备了在PEG和PNIPAM两嵌段之间带有叠氮基团的ABA三嵌段共聚物;然后利用双炔基小分子与叠氮基团在极高的浓度下发生聚合物分子内关环反应,制备了全亲水性蝌蚪形聚合物。研究了蝌蚪形共聚物和线形前体的温度响应性行为的差别,研究了浓度对聚合物温度响应行为的影响。结果表明,环状聚合物的临界聚集温度与其相同分子量的线形前体聚合物的临界聚集温度相比较高,溶液浓度越高,聚合物的临界聚集温度越低。2.改变PNIPAM以及PEG链段的长度,研究聚合物结构对合成双尾蝌蚪形聚合物的影响,详细探讨了聚合物结构的改变对其温度响应行为的影响。利用光散射对聚合物的宏观温度响应行为进行了表征,利用温度骤变的停-留光谱研究了聚合物的微观温度响应行为。研究结果均表明,增加PEG亲水链段的分子量或者降低PNIPAM链段的分子量,对聚合物的温度响应行为具有相同的影响,均使得溶液的散射光强变弱,相转变温度升高。双尾蝌蚪形聚合物的聚集行为强烈依赖于共聚物的链段长度比。3.利用原子转移自由基聚合、开环聚合以及点击反应相结合,成功合成了Y-形杂臂嵌段共聚物,聚(N-异丙基丙烯酰胺)-b-聚(赖氨酸)2 (PNIPAM-b-PLL2),研究了此共聚物在水溶液中的胶束化行为以及刺激响应行为。将共聚物胶束交联,得到结构稳定的壳交联胶束,通过改变温度以及交联度控制药物的释放行为。研究结果表明,随着交联程度的降低或者温度的升高,药物释放速度变快。4.利用单电子自由基聚合、原子转移自由基聚合以及点击反应相结合,成功制备了一系列H-形嵌段共聚物,聚甲基丙烯酸二甲胺基乙酯/聚(N-异丙基丙烯酰胺)-b-聚乙二醇-b-聚甲基丙烯酸二甲胺基乙酯/聚(N-异丙基丙烯酰胺) (PNIPAM/PDMAEMA)-b-PEG-b-(PNIPAM/PDMAEMA)。利用原位还原的方法制备表面接枝H-形嵌段共聚物的金纳米粒子。研究聚合物的结构、溶液的pH条件以及[DMAEMA]:[AuCl4-]对金纳米粒子的性能影响,研究此金纳米粒子的温度以及pH响应行为。研究结果表明,相同条件下,随着PDMAEMA链段长度的降低,所得的金纳米粒子尺寸增加;[DMAEMA]:[AuCl4-]摩尔比的增加,所得的金纳米粒子尺寸增加;溶液pH的增加,所得到的金纳米粒子尺寸变大。在酸性或者中性条件下,所得金纳米粒子的温度响应性行为较弱;碱性条件下,所得金纳米粒子的温度响应性行为较强。5.利用开环聚合以及原子转移自由基聚合相结合,制备了嵌段共聚物聚(N-异丙基丙烯酰胺)-b-聚赖氨酸(PNIPAM-b-PLL)。通过柠檬酸钠还原的方法制备了尺寸稳定的金纳米粒子,利用赖氨酸与金纳米粒子的作用,得到表面修饰嵌段聚合物的金纳米粒子。研究这类金纳米粒子的温度以及pH响应行为,研究结果表明,酸性以及中性条件下,所得到的金纳米粒子的温度响应性行为较弱;碱性条件下,金纳米粒子的温度响应性行为较强。聚赖氨酸接枝到金纳米粒子的表面后,其构象未发生变化。更多还原

【Abstract】 Polymer materials have been applied extensively in many fields, including space technologies, military industry, domestic livings and so on. With the progress of polymer and material sciences, new requirements for polymer synthetic technology, such as controllability, high efficiency and high selectivity, are presented. According to those requirements, newly developed techniques, such as controlled free radical polymerization and“click chemistry”, have been poured with great passion by the scientists. These techniques provide the scientists with powerful methods to synthesize various special-structured polymers as well as various organic/inorganic materials. Smart 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 research of the precursors, this dissertation describes several interesting researches in the synthesis of topologically structured polymers and the modification of nanomaterials. The main results obtained in this thesis are as followed.1. Twin-tail tadpole-shaped copolymer tail-PNIPAM-c-PEG [PNIPAM: poly(N-propylacrylamide), PEG [poly(ethylene gylocl)] was synthesized by the combination of SET-LRP (single-electron-transfer living radical polymerization) and“click chemistry”. Firstly, we synthesized PNIPAM-b-PEG-b-PNIPAM with two azide side groups anchored at the junctions between PEG and PNIPAM blocks. Secondly, under high concentration, intrachain connection of the block junctions by dipropargyl oxalylate was done through click reaction. The thermal phase transition behaviors of twin-tail tadpole-shaped polymers and their linear precursors were investigated. We also studied the influence of polymer concentration on the thermal phase transition behaviors. It is shown that the lower critical solution temperature (LCST) values of cyclic polymers were higher than that of their linear precursors with the same block lengths. Polymers have lower LCST values under higher polymer concentration.2. We investigated the influence of varying block length of PEG chain and PNIPAM chains on the formation of twin-tail tadpole-shaped hydrophilic copolymers. The stability, structure and growth kinetics of the micelles formed from tail-(PNIPAM)2-c-PEG and its linear precursor with varying PEG and PNIPAM chains were studied in detail using stop-flow temperature jump technique and dynamic/static laser light. The study of temperature-jumped stop-flow was performed in the fast heating process to investigate the temperature-responsive behaviors. The results show that the thermal-induced re-organization of the micelles depends strongly on the topology and block length of those block copolymers.3. Combining with ATRP (Atom Transfer Radical Polymerization), ROP (ring-opening polymerization) and“click chemistry”, we successfully synthesized well-defined Y-shaped copolymer PNIPAM-b-PLL2. [PLL: poly(L-lysine)]. Temperature and pH-responsive behavior of the core-shell micelles were studied. Structural stable micelles were obtained through the shell cross-linking of the micelles. These shell-cross-linked micelles were used as drug nanocarriers and the release profile was dually controlled by the solution temperature and the cross-linking degree. Decreasing the cross-linking degree or increasing temperature could accelerate the drug release rate.4. H-shaped copolymer (PNIPAM/PDMAEMA)-b-PEG-b-(PNIPAM/PDMAEMA) [PDMAEMA: poly(N,N-dimeythylaminoethyl methacrylate)] has been successfully prepared through a combination of SET-LRP, ATRP and“Click chemistry”. These copolymers were employed to in suti prepare stable colloidal gold nanoparticles in aqueous solution without any external reducing agent. The formation of gold nanoparticles was affected by the length of PDMAEMA block, the feed ratio of the copolymer to HAuCl4 and the pH value. We also studied the temperature and pH responsive behaviors of the polymer-capped gold nanoparticles. The study results shows that with increasing PDMAEMA chains length, increasing [DMAEMA]:[AuCl4-] or increasing the solution pH values, the diameter of gold nanoparticles become bigger. Under acidic or neutral conditions, LCST of gold nanoparticles protected with polymers are higher, and their temperature-responsive behaviors is weaker, while under alkalic conditions, LCST of gold nanoparticles protected with polymers are lower, and temperature-responsive behavior of gold nanoparticles is stronger.5. Block copolymers PNIPAM-b-PLL were synthesized by the combination of ATRP and ROP. Gold nanoparticles were prepared through the common technique of citrate reduction and stabilized through the interaction of lysine residues of PLL with the gold surface. Gold nanoparticles protected with stimuli-sensitive copolymer PNIPAM-b-PLL were studied as a function of pH and temperature. Under acidic or neutral conditions, LCST of gold nanoparticles protected with polymers were higher. Gold nanoparticles didn’t affect the secondary structure of PLL chains.更多还原