Department of Chemistry, McGill University, Montreal, Quebec, Canada.
Acc Chem Res. 2012 Oct 16;45(10):1657-66. doi: 10.1021/ar2003144. Epub 2012 Jul 30.
The development of nanodevices currently requires the formation of morphologically controlled or highly ordered arrays of metal, semiconducting, or magnetic nanoparticles. In this context, polymer self-assembly provides a powerful bottom-up approach for constructing these materials. The self-assembly of block copolymers (BCPs) in solution is a facile and popular method for the preparation of aggregates of controllable morphologies, including spherical micelles, cylindrical micelles, vesicles (or polymersomes), thin films, and other complex structures that range from zero to three dimensions. Researchers can generally control the morphology of the aggregates by varying copolymer composition or environmental parameters, including the copolymer concentration, the common solvent, the content of the precipitant, or the presence of additives such as ions, among others. For example, as the content of the hydrophilic block in amphiphilic copolymers decreases, the aggregates formed from the copolymers can change from spherical micelles to cylindrical micelles and to vesicles. The aggregates of various morphologies provide excellent templates for the organization of the nanoparticles. The presence of various domains, such as cores, interfaces, and coronas, in BCP aggregates allows for selective localization of nanoparticles in different regions, which may critically affect the resulting properties and applications of the nanoparticles. For example, the incorporation of quantum dots (QDs) into micelle cores solves many problems encountered in the utilization of QDs in biological environments, including enhancement of water solubility, aggregation prevention, increases in circulation or retention time, and toxicity clearance. Simultaneously it preserves the unique optical performance of QDs compared with those of organic fluorophores, such as size-tunable light emission, improved signal brightness, resistance against photobleaching, and simultaneous excitation of multiple fluorescence colors. Therefore, many studies have focused on the selective localization of nanoparticles in BCP aggregates. This Account describes the selective localization of preformed spherical nanoparticles in different domains of BCP aggregates of controllable morphologies in solution, including spherical micelles, cylindrical micelles, and vesicles. These structures offer many potential applications in biotechnology, biomedicine, catalysis, etc. We also introduce other types of control, including interparticle spacing, particle number density, or aggregate size control. We highlight examples in which the surface coating, volume fraction, or size of the particles was tailored to precisely control incorporation. These examples build on the thermodynamic considerations of particle-polymer interactions, such as hydrophobic interactions, hydrogen bonding, electrostatic interactions, and ligand replacement, among others.
纳米器件的发展目前需要形成形态控制或高度有序的金属、半导体或磁性纳米粒子阵列。在这种情况下，聚合物自组装为构建这些材料提供了一种强大的自下而上的方法。嵌段共聚物（BCP）在溶液中的自组装是制备具有可控形态的聚集体的一种简单而流行的方法，包括球形胶束、圆柱形胶束、囊泡（或聚合物囊泡）、薄膜和其他从零维到三维的复杂结构。研究人员通常可以通过改变共聚物组成或环境参数来控制聚集体的形态，包括共聚物浓度、常用溶剂、沉淀剂含量或添加离子等添加剂。例如，随着两亲性共聚物中亲水性嵌段含量的降低，共聚物形成的聚集体可以从球形胶束变为圆柱形胶束，再变为囊泡。各种形态的聚集体为纳米粒子的组织提供了极好的模板。BCP 聚集体中存在各种畴，如核、界面和冠，允许纳米粒子选择性地定位于不同区域，这可能会对纳米粒子的最终性质和应用产生至关重要的影响。例如，将量子点 (QD) 掺入胶束核中解决了在生物环境中使用 QD 时遇到的许多问题，包括增强水溶性、防止聚集、增加循环或保留时间以及清除毒性。同时，与有机荧光团相比，它保留了 QD 的独特光学性能，例如可调谐的光发射、提高的信号亮度、抗光漂白和同时激发多种荧光颜色。因此，许多研究都集中在纳米粒子在 BCP 聚集体中的选择性定位上。本综述描述了在溶液中形态可控的 BCP 聚集体中不同区域选择性地定位预先形成的球形纳米粒子，包括球形胶束、圆柱形胶束和囊泡。这些结构在生物技术、生物医学、催化等领域具有许多潜在的应用。我们还介绍了其他类型的控制，包括粒子间间距、粒子数密度或聚集体尺寸控制。我们强调了一些例子，其中通过表面涂层、体积分数或颗粒尺寸来精确控制颗粒的掺入。这些例子建立在对粒子-聚合物相互作用的热力学考虑的基础上，例如疏水性相互作用、氢键、静电相互作用和配体取代等。
