Department of Chemistry, The University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom.
J Am Chem Soc. 2011 Oct 19;133(41):16581-7. doi: 10.1021/ja206301a. Epub 2011 Sep 9.
Amphiphilic diblock copolymers composed of two covalently linked, chemically distinct chains can be considered to be biological mimics of cell membrane-forming lipid molecules, but with typically more than an order of magnitude increase in molecular weight. These macromolecular amphiphiles are known to form a wide range of nanostructures (spheres, worms, vesicles, etc.) in solvents that are selective for one of the blocks. However, such self-assembly is usually limited to dilute copolymer solutions (<1%), which is a significant disadvantage for potential commercial applications such as drug delivery and coatings. In principle, this problem can be circumvented by polymerization-induced block copolymer self-assembly. Here we detail the synthesis and subsequent in situ self-assembly of amphiphilic AB diblock copolymers in a one pot concentrated aqueous dispersion polymerization formulation. We show that spherical micelles, wormlike micelles, and vesicles can be predictably and efficiently obtained (within 2 h of polymerization, >99% monomer conversion) at relatively high solids in purely aqueous solution. Furthermore, careful monitoring of the in situ polymerization by transmission electron microscopy reveals various novel intermediate structures (including branched worms, partially coalesced worms, nascent bilayers, "octopi", "jellyfish", and finally pure vesicles) that provide important mechanistic insights regarding the evolution of the particle morphology during the sphere-to-worm and worm-to-vesicle transitions. This environmentally benign approach (which involves no toxic solvents, is conducted at relatively high solids, and requires no additional processing) is readily amenable to industrial scale-up, since it is based on commercially available starting materials.
由两条共价键连接的、化学性质不同的链组成的两亲性嵌段共聚物可以被认为是细胞膜形成脂质分子的生物模拟物，但分子量通常增加了一个数量级以上。这些高分子两亲物已知在对其中一个嵌段具有选择性的溶剂中形成广泛的纳米结构（球体、蠕虫、囊泡等）。然而，这种自组装通常限于稀释的共聚物溶液（<1%），这对于潜在的商业应用（如药物输送和涂层）是一个显著的缺点。原则上，这个问题可以通过聚合诱导的嵌段共聚物自组装来规避。在这里，我们详细描述了在一锅浓缩的水溶液聚合配方中两亲性 AB 嵌段共聚物的合成和随后的原位自组装。我们表明，可以在相对高的固含量下（聚合 2 小时内，单体转化率>99%）在纯水溶液中可预测且有效地得到球形胶束、蠕虫状胶束和囊泡。此外，通过透射电子显微镜对原位聚合的仔细监测揭示了各种新颖的中间结构（包括支化蠕虫、部分聚结的蠕虫、初生双层、“章鱼”、“水母”，最终为纯囊泡），这为在球到蠕虫和蠕虫到囊泡转变过程中颗粒形态的演变提供了重要的机制见解。这种环境友好的方法（不涉及有毒溶剂，在相对高的固含量下进行，并且不需要额外的处理）易于进行工业放大，因为它基于商业上可用的起始材料。
