Iatridi Zacharoula, Bokias Georgios
Department of Chemistry, University of Patras, GR-26504 Patras, Greece.
Langmuir. 2009 Jul 7;25(13):7695-703. doi: 10.1021/la900390y.
The preparation of temperature-sensitive water-soluble hybrid organic/inorganic nanoparticles, exploiting the complexation of Cu2+ ions with PANa-g-PNIPAMx comb-type copolymers, is presented. These copolymers consist of a Cu2+-complexing poly(sodium acrylate) backbone, PANa, and thermosensitive poly(N-isopropylacrylamide), PNIPAM, side chains. UV-vis spectrophotometry verified that the polymer/Cu2+ complexation follows a charge neutralization process, while turbidimetry revealed that the complexes formed can indeed be stabilized in water, provided that copolymers with a sufficiently high PNIPAM content (x approximately 80 mol % in monomer units) are used. Dilute solution viscometry and dynamic light scattering indicated that the hydrodynamic dimensions of the hybrid polymer/Cu2+ nanoparticles decrease substantially upon heating, reflecting the lower critical solution temperature behavior of the PNIPAM side chains. However, when the net negative charge of the hybrid polymer/Cu2+ nanoparticles decreases, interparticle aggregation and, eventually, phase separation may take place. In semidilute aqueous solution, the complexation of the polymer backbone with Cu2+ ions effectively controls the thermothickening properties of the thermosensitive comb-type PANa-g-PNIPAM copolymers. Finally, the temperature-induced formation of a compartmentalized hydrophilic-hydrophobic nanocontainer, where the hydrophilic and the hydrophobic compartments can be loaded with Cu2+ ions and hydrophobic substances, respectively, was evidenced through pyrene fluorescence probing.
本文介绍了利用Cu²⁺离子与聚丙烯酸钠接枝聚N-异丙基丙烯酰胺x梳型共聚物（PANa-g-PNIPAMx）的络合作用制备温度敏感型水溶性有机/无机杂化纳米粒子的方法。这些共聚物由与Cu²⁺络合的聚丙烯酸钠主链（PANa）和热敏性聚N-异丙基丙烯酰胺（PNIPAM）侧链组成。紫外-可见分光光度法证实聚合物/Cu²⁺络合遵循电荷中和过程，而比浊法表明，只要使用具有足够高PNIPAM含量（单体单元中x约为80 mol%）的共聚物，形成的络合物确实可以在水中稳定存在。稀溶液粘度测定法和动态光散射表明，杂化聚合物/Cu²⁺纳米粒子的流体动力学尺寸在加热时会大幅减小，这反映了PNIPAM侧链的低临界溶液温度行为。然而，当杂化聚合物/Cu²⁺纳米粒子的净负电荷减少时，粒子间可能会发生聚集并最终导致相分离。在半稀水溶液中，聚合物主链与Cu²⁺离子的络合有效地控制了热敏性梳型PANa-g-PNIPAM共聚物的热增稠性能。最后，通过芘荧光探针证实了温度诱导形成了一种分隔的亲水-疏水纳米容器，其中亲水和疏水隔室可分别负载Cu²⁺离子和疏水性物质。
