Nuopponen Markus, Tenhu Heikki
Laboratory of Polymer Chemistry, University of Helsinki, PB 55, FIN-00014 HY, Finland.
Langmuir. 2007 May 8;23(10):5352-7. doi: 10.1021/la063240m. Epub 2007 Apr 13.
Aqueous dispersions of gold nanoparticles protected with a stimuli-sensitive diblock copolymer were studied as a function of pH and temperature. Poly(methacrylic acid)-block-poly(N-isopropylacrylamide), PMAA-b-PNIPAM, copolymer was synthesized using the RAFT technique. A one-pot method utilizing the dithiobenzoate functionalized polymer was used to prepare gold nanoparticles protected with PMAA-b-PNIPAM. The gold nanoparticles coated with block copolymers, with the PNIPAM block bound to the particle surface and PMAA as an outer block form stimuli-sensitive aggregates in water. The changes in the absorption maxima of the surface plasmon resonance, SPR, of the gold particles and in the size of the aggregates were investigated as a function of pH and temperature. pH was observed to affect the size of the aggregates, whereas the effect of temperature was moderate. However, a blue shift in the SPR was observed both with decreasing pH and increasing temperature. Whereas the PMAA blocks control the colloidal stability of the particles and their aggregates, the thermo-sensitive PNIPAM blocks have a noticeable effect on the polarity of the immediate surroundings of the particles.
研究了用刺激响应性二嵌段共聚物保护的金纳米颗粒水分散体随pH值和温度的变化。采用可逆加成-断裂链转移（RAFT）技术合成了聚（甲基丙烯酸）-嵌段-聚（N-异丙基丙烯酰胺），即PMAA-b-PNIPAM共聚物。利用二硫代苯甲酸官能化聚合物的一锅法制备了用PMAA-b-PNIPAM保护的金纳米颗粒。涂有嵌段共聚物的金纳米颗粒，其中PNIPAM嵌段结合在颗粒表面，PMAA作为外层嵌段，在水中形成刺激响应性聚集体。研究了金颗粒表面等离子体共振（SPR）吸收最大值的变化以及聚集体尺寸随pH值和温度的变化。观察到pH值会影响聚集体的尺寸，而温度的影响适中。然而，随着pH值降低和温度升高，SPR均出现蓝移。虽然PMAA嵌段控制颗粒及其聚集体的胶体稳定性，但热敏性PNIPAM嵌段对颗粒紧邻环境的极性有显著影响。
