PEO-PPO-PEO嵌段共聚物自组装及其在纳米材料中的应用
文献类型：学位论文
| 作者 | 陈澍 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-06-11 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 刘会洲 |
| 关键词 | PEO-PPO-PEO嵌段共聚物 自组装 纳米材料 氢键 胶团 囊泡 热力学模型 磁性载体 药物控释 |
| 其他题名 | Self-Assembly of PEO-PPO-PEO Block Copolymers and Its Applications on Nanomaterials |
| 学位专业 | 化学工艺 |
| 中文摘要 | 聚氧乙烯–聚氧丙烯–聚氧乙烯(PEO–PPO–PEO)嵌段共聚物在选择性溶剂中可以自组装形成形貌和性质丰富的介观结构，具有生物相容、结构可控和温度敏感等优点，是制备纳米材料的理想元件。本论文围绕着PEO-PPO-PEO嵌段共聚物的自组装性质，在深入研究PEO-PPO-PEO嵌段共聚物胶团和囊泡的形成机理的基础上，将其自组装性质应用到金纳米颗粒的可控制备和磁性纳米颗粒的功能化中。利用各种光谱技术和耗散粒子动力学模拟，揭示了PEO-PPO-PEO嵌段共聚物与无机纳米颗粒的相互作用及其对纳米结构的调控机理。 研究内容主要包括以下五个方面： (1) 构建了描述双亲嵌段共聚物水溶液中胶团化过程氢键作用的热力学模型，为定量研究胶团化过程中氢键作用引起的熵贡献提供了的理论工具。结果表明，随着温度升高或浓度增大，嵌段共聚物与水分子间的氢键断裂，引起的体系的混合熵增加，推动了PEO-PPO-PEO嵌段共聚物胶团的形成。PO-水氢键对胶团化熵变的贡献远大于EO-水氢键的贡献，是胶团化的主导驱动力。 (2) 发现了使PEO-PPO-PEO嵌段共聚物自组装为囊泡结构的新方法。在PEO-PPO-PEO嵌段共聚物水溶液中添加少量阴离子表面活性剂和无机盐，嵌段共聚物就可以自发形成平均直径为800 nm的中空囊泡结构，简单经济。化学交联进一步提高了囊泡的稳定性，经50倍稀释之后，交联囊泡的性质没有明显改变。从体系各组分间疏水相互作用的角度提出了囊泡形成的机理。PEO-PPO-PEO 嵌段共聚物水溶液中的胶团首先被十二烷基硫酸钠(SDS)的吸附而破坏。由于SDS分子间的静电斥力，PEO-PPO-PEO嵌段共聚物被吸附在PO嵌段上的SDS拉伸成单体状态，形成类似项链形状的聚集体，使得PEO-PPO-PEO嵌段共聚物具有了“离子型表面活性剂”的特点。NaF的加入会屏蔽吸附在PO嵌段上的SDS之间的静电斥力，使PO嵌段间的疏水相互作用增强，堆积更加紧密，改变了聚集体的堆积参数，从而推动了“项链”状聚集体发生折叠转变为囊泡结构。 (3) 发展了以PEO-PPO-PEO嵌段共聚物胶团为模板可控合成金纳米颗粒的新方法。该方法环境友好、经济简单。通过调节聚合物浓度、分子量、嵌段比例及加入无机盐添加剂，可以很好地控制金纳米颗粒的粒径和性质。随着嵌段共聚物浓度、分子量和PO嵌段比例的增加，金纳米颗粒粒径变小、粒度变均匀、稳定性变好。少量无机盐的加入是提高金纳米颗粒单分散性和稳定性的经济有效的方法。提出了胶团内部疏水微环境对金纳米颗粒的形貌及稳定性的控制机理：胶团内部疏水性越强，对金纳米颗粒稳定作用就越强，制备的金纳米颗粒的粒径越小、粒度越均匀。 (4) 用耗散粒子动力学的方法模拟了金/PEO-PPO-PEO嵌段共聚物纳米颗粒的结构和形成动力学。还原反应初期形成的金纳米团簇的聚集过程与嵌段共聚物胶团的空间稳定作用之间的竞争，控制最终形成的金纳米颗粒的性质。随着嵌段共聚物浓度、分子量和PO嵌段比例的增加，模拟所得的金颗粒粒径变小且均匀，稳定性增强。通过计算金/PEO-PPO-PEO嵌段共聚物颗粒中各组分的密度分布，发现在金纳米颗粒粒径小且粒度均一的体系中，金/嵌段共聚物颗粒内核的水含量都较少，疏水性较强。进一步证实了嵌段共聚物与纳米颗粒的相互作用及胶团内部疏水性质对金纳米颗粒的控制机理。 (5) 利用PEO-PPO-PEO嵌段共聚物温度敏感的自组装性质使氧化铁纳米颗粒表面功能化，制备了温度敏感型磁性纳米载体，用于靶向药物输送。磁性/PEO-PPO-PEO嵌段共聚物复合纳米颗粒具有温度响应性质。在人体温度附近，随着温度的升高，PEO-PPO-PEO嵌段共聚物在氧化铁纳米颗粒表面发生从完全伸展到紧密卷曲的转变，导致磁性纳米颗粒的水力学半径迅速减小。因此，磁性纳米颗粒聚合物壳层具有温度控制的开关性质，从而可以调控药物分子的吸附量与释放速度。体外实验证明，模型药物的吸附量和释放速率可以通过调节温度很好地控制。在模拟人体环境下，可以实现3天的药物缓释效果，克服了普通磁性纳米载体对药物释放过快的缺点。初期动物实验表明，该载体附载了治疗神经纤维损伤的药物之后，能提高大鼠脊髓损伤区域神经纤维的修复速度。 |
| 英文摘要 | Poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymers could self-assemble into several types of mesostructure with various morphologies and properties in selective solvents. The PEO-PPO-PEO block copolymers have many attractive advantages which makes them ideal building blocks of nanomaterials, for example, temperature-responsivity, biocompatability, and the self-assembled strucutrues could be well controlled by varying the copolymer composition or adding additives. This thesis aims at studying the formation mechanism of micelles and vesicles in PEO-PPO-PEO block copolymers aqueous solutions, and applying their self-assembly behavior into controallble preparation of gold nanoparticles and functionalization of magnetic nanoparticles. Using several spectroscopic techniques and mesoscale dissipative particle dynamic simulations, the controlling mechanism of the nanoparticles is further disclosed as well as the interaction between PEO-PPO-PEO block copolymers and the inoganic nanoparticles. The main results are as follows: (1) A thermodynamic model is developed to study the quantitative contribution of hydrogen bonding between PEO-PPO-PEO block copolymer and water molecuels to the temperature dependent micellization. The entropic change due to hydrogen bonding is formulated and the individual contribution of EO-Water and PO-Water hydrogen bonding to the micellization are derived respectively. Increase of the temperature leads to the disruption of hydrogen bonds, which results in a sharp increase in the mixing entropy. PO-Water hydrogen bonding is more sensitive to temperature than EO-Water hydrogen bonding, and therefore plays a dominative role in the temperature dependent micellization. (2) A novel method has been developed to prepare vesicles from aqueous solutions of PEO-PPO-PEO block copolymer, anionic surfactant sodium dodecyl sulfate (SDS) and inorganic salt NaF. The obtained vesicles are spherical in shape with hollow structures, and the average diameter of vesicles is about 800 nm with 50 nm thick walls. The spontaneously formed vesicles were further chemically cross-linked, and were proved very stable against serious dilution after cross-linking. By detecting the hydrophobic interactions between the block copolymers and the microenvironments arround the vesicles using several spectroscopic techniques, the vesicle formation mechanism was disclosed as the follows: the micelles of PEO-PPO-PEO block copolymers were firstly destroyed by addition of SDS aniornic surfactant. The unassociated block copolymers and SDS micelles formed necklace-like complexes. Induced by addition of NaF salt, the “ionic” complexes further folded into vesicles due to shielding of the electrostatic repulsion between SDS. (3) A novel method of controlled preparation of gold nanoparticles has been developed from aqueous solutions of PEO-PPO-PEO block copolyers. Using micelles of PEO-PPO-PEO block copolymers as templates, the size and stability of gold nanoparticles could be well controlled by tuning the block copolymer concentration and composition and by adding inorganic salt NaF. As the concentration or molecular weight of the copolymer increasing, the gold nanoparticles become more spherical, smaller and uniform in size. Addition of a little NaF could significantly improve stability of the nonoparticles. Using FTIR and 1H-NMR spectroscopy, the micellization of the block copolymers and hydrophobicity of the micelles were proven very important for the stabilization. A higher hydrophobicity of the micelle cores was expected to favor the entrapment of primary gold clusters and the stabilization of gold nanoparticles. (4) Dissipative particle dynamics (DPD) was employed to simulate the formation dynamics and structures of gold nanoparticles in PEO-PPO-PEO block copolymer micelles. It showed that gold beads were wrapped by the block copolymer and aggregated into spherical particles inside the micelles, forming stable gold/PEO-PPO-PEO block copolymer colloids. Dynamic process indicated that the formation of gold nanoparticles was controlled by the competition between aggregation of primary gold clusters and the stabilization by micelles of block copolymers. Increasing the copolymer concentration, molecular weight and PO block length led to the formation of more uniform and more stable gold nanoparticles. The DPD simulations agreeed well with previous experiments, while more structure information on microscopic level could be provided. The calculated density distribution of each bead indicated that the hydrophobicity inside PEO-PPO-PEO block copolymer micelles plays a decisive role in the entrapment of primary gold clusters and stabilization of gold nanoparticles. Increasing the hydrophobicity inside micelles favored the stabilization and the formation of uniform gold nanoparticles. (5) Temperature responsive magnetite/polymer nanoparticles have been developed from iron oxide nanoparticles and poly(ethyleneimine) modified PEO-PPO-PEO block copolymer. The most attractive feature of the nanoparticles is their temperature-responsive volume transition property. The hydrodynamic diameter of the nanoparticles underwent a sharp decrease from 45 nm to 25 nm while the temperature was changed from 20 oC to 35 oC. The reason could be attributed to a thermo-induced self-assembly of the immobilized block copolymers occurred on the magnetite solid surfaces, which is accompanied by a conformational change from fully extended state to highly coiled state of the copolymer. Consequently, the copolymer shell could act as a temperature controlled “gate” for the transit of guest molecules. The uptake and release of model drug were well controlled by switching the transient opening and closing of the polymer shell at different temperature. Sustained release of about three days was achieved in simulated human body conditions. In primary mouse experiments, drug entrapped magnetic nanoparticles showed good biocompatibility and effective therapy of spinal cord damage. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 161 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1250]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 陈澍. PEO-PPO-PEO嵌段共聚物自组装及其在纳米材料中的应用[D]. 过程工程研究所. 中国科学院过程工程研究所. 2008. |
入库方式： OAI收割
来源：过程工程研究所
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