Pilon Laura N, Armes Steven P, Findlay Paul, Rannard Steven P
Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom.
Langmuir. 2005 Apr 26;21(9):3808-13. doi: 10.1021/la047046g.
Shell cross-linked (SCL) micelles with hydroxy-functional coronas have been constructed in aqueous solution by exploiting the micellar self-assembly behavior of a new thermoresponsive ABC triblock copolymer. This copolymer was prepared via atom transfer radical polymerization in a convenient one-pot synthesis and comprised a thermoresponsive core-forming poly(propylene oxide) (PPO) block, a cross-linkable central poly(2-(dimethylamino)ethyl methacrylate) (DMA) block, and a hydroxy-functional outer block based on poly(glycerol monomethacrylate) (GMA). DMF GPC analysis confirmed a unimodal molecular weight distribution for the PPO-PDMA-PGMA triblock copolymer precursor, with an M(n) of 12 100 and a polydispersity of approximately 1.26. This copolymer dissolved molecularly in aqueous solution at 5 degrees C but formed micelles with hydroxy-functional coronas above a critical micelle temperature of around 12 degrees C, which corresponded closely to the cloud point of the PPO macroinitiator. Cross-linking of the DMA residues using 1,2-bis(2-iodoethoxy)ethane produced SCL micelles that remained intact at 5 degrees C, i.e., below the cloud point of the core-forming PPO block. Dynamic light scattering studies confirmed that the SCL micelle diameter could be varied depending on the temperature employed for cross-linking: smaller, more compact SCL micelles were formed at higher temperatures, as expected. Since cross-linking involved quaternization of the DMA residues, the SCL micelles acquired cationic surface charge as judged by aqueous electrophoresis studies. These cationic SCL micelles were adsorbed onto near-monodisperse anionic silica sols, which were used as a model colloidal substrate. Thermogravimetric analyses indicated a SCL micelle mass loading of 2.5-4.4%, depending on the silica sol diameter and the initial micelle concentration. Aqueous electrophoresis measurements confirmed that surface charge reversal occurred after adsorption of the SCL micelles, and scanning electron microscopy studies revealed a uniform coating of SCL micelles on the silica particles.
通过利用一种新型热响应性ABC三嵌段共聚物的胶束自组装行为，在水溶液中构建了具有羟基官能化冠层的壳交联（SCL）胶束。这种共聚物通过原子转移自由基聚合以方便的一锅法合成制备，由热响应性的形成核的聚环氧丙烷（PPO）嵌段、可交联的中心聚甲基丙烯酸2-（二甲氨基）乙酯（DMA）嵌段和基于聚甘油单甲基丙烯酸酯（GMA）的羟基官能化外层嵌段组成。DMF GPC分析证实了PPO-PDMA-PGMA三嵌段共聚物前体的单峰分子量分布，数均分子量（M(n)）为12100，多分散性约为1.26。该共聚物在5℃时以分子形式溶解于水溶液中，但在约12℃的临界胶束温度以上形成具有羟基官能化冠层的胶束，这与PPO大分子引发剂的浊点密切对应。使用1,2-双（2-碘乙氧基）乙烷对DMA残基进行交联产生了在5℃下保持完整的SCL胶束，即低于形成核的PPO嵌段的浊点。动态光散射研究证实，SCL胶束直径可根据用于交联的温度而变化：正如预期的那样，在较高温度下形成更小、更致密的SCL胶束。由于交联涉及DMA残基的季铵化，通过水性电泳研究判断，SCL胶束获得了阳离子表面电荷。这些阳离子SCL胶束被吸附到近单分散的阴离子二氧化硅溶胶上，后者用作模型胶体基质。热重分析表明，根据二氧化硅溶胶直径和初始胶束浓度，SCL胶束的质量负载量为2.5-4.4%。水性电泳测量证实，在吸附SCL胶束后发生了表面电荷反转，扫描电子显微镜研究显示SCL胶束在二氧化硅颗粒上形成了均匀涂层。
