Nyström Andreas M, Bartels Jeremy W, Du Wenjun, Wooley Karen L
Department of Chemistry and Department of Radiology, Washington University in Saint Louis, Saint Louis, Missouri 63130-4899 (USA).
J Polym Sci A Polym Chem. 2009 Feb 12;47(4):1023-1037. doi: 10.1002/pola.23184.
Reversible addition-fragmentation chain transfer polymerization was employed to synthesize a set of copolymers of styrene (PS) and 2,3,4,5,6-pentafluorostyrene (PPFS), as well as block copolymers with tert-butyl acrylate (PtBA)-b-PS-co-PPFS, with control over molecular weight and polydispersity. It was found that the copolymerization of styrene and PFS allowed for the preparation of gradient copolymers with opposite levels of monomer consumption, depending on the feed ratio. Conversion to amphiphilic block copolymers, PAA-b-(PS-co-PPFS), by removing the protecting groups was followed by fitting with monomethoxy poly(ethylene glycol) chains. Solution-state assembly and intramicellar crosslinking afforded shell crosslinked (SCK) block copolymer nanoparticles. These fluorinated nanoparticles (ca. 20 nm diameters) were studied as potential magnetic resonance imaging (MRI) contrast agents based on the (19)F-nuclei, however, it was found that packaging of the hydrophobic fluorinated polymers into the core domain restricted the mobility of the chains and prohibited (19)F-NMR spectroscopy when the particles were dispersed in water without an organic cosolvent. Packing of perflouro-15-crown-5-ether (PFCE) into the polymer micelle was demonstrated with good uptake efficiency, however, it was necessary to swell the core with a good solvent (DMSO) to increase the mobility and observe the (19)F-NMR signal of the PFCE.
采用可逆加成-断裂链转移聚合方法合成了一组苯乙烯（PS）与2,3,4,5,6-五氟苯乙烯（PPFS）的共聚物，以及丙烯酸叔丁酯-b-PS-co-PPFS嵌段共聚物，实现了对分子量和多分散性的控制。研究发现，根据进料比，苯乙烯与PFS的共聚反应能够制备出具有相反单体消耗水平的梯度共聚物。通过去除保护基团将其转化为两亲性嵌段共聚物PAA-b-(PS-co-PPFS)，然后接上单甲氧基聚（乙二醇）链。溶液态组装和胶束内交联得到了壳交联（SCK）嵌段共聚物纳米粒子。对这些直径约20 nm的氟化纳米粒子作为基于（19）F核的潜在磁共振成像（MRI）造影剂进行了研究，然而，研究发现，当粒子分散在没有有机共溶剂的水中时，将疏水性氟化聚合物包装到核域中会限制链的流动性，并阻碍（19）F-NMR光谱分析。已证明全氟-15-冠-5-醚（PFCE）能以良好的摄取效率包装到聚合物胶束中，然而，有必要用良溶剂（DMSO）使核膨胀以增加流动性并观察PFCE的（19）F-NMR信号。
