Kríz Jaroslav, Plestil Josef, Pospísil Herman, Kadlec Petr, Konák Cestmír, Almásy László, Kuklin Alexander I
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, 162 06 Prague 6, Czech Republic.
Langmuir. 2004 Dec 7;20(25):11255-63. doi: 10.1021/la0481849.
Three-layer nanoparticles were prepared by radiation-induced polymerization of 1-10 g/L of methyl methacrylate dissolved in a 0.1 wt % D(2)O solution of polystyrene-poly(methacrylic acid) (PS-PMA) micelles. According to NMR and small-angle neutron scattering (SANS), most of the poly(methyl methacrylate) (PMMA) is adsorbed at the core-shell interface of the particles. A small fraction of shorter PMMA probably sticks to outer parts of the PMA chains. The absorption kinetics and equilibria of benzene and chloroform were studied by NMR and SANS time-resolved experiments. The diffusion front in the PS core is very narrow but quite broad in the PMMA sheet suggesting, thus, a less compact state of PMMA. According to SANS, the diffusion kinetics is almost independent of the PMMA sheet thickness. In contrast to it, the absorption capacity, reflected by both SANS and NMR, increases markedly with the PMMA content in the particle. The maximum amount of solubilized compound depends on its positive interaction with PMMA (expressed by the chi parameter) but is restricted by the growing interface tension between swollen PMMA and D(2)O. In accordance with this conclusion, a particle saturated with benzene can absorb chloroform only at the expense of a part of benzene expelled into the surrounding medium and vice versa. Starting with 10 g PMMA/L (10 times the weight of the original micelles), the particles become unstable when being swollen with a good solvent.
通过辐射诱导溶解在聚苯乙烯 - 聚（甲基丙烯酸）（PS - PMA）胶束的0.1 wt％ D₂O溶液中的1 - 10 g/L甲基丙烯酸甲酯进行聚合反应，制备了三层纳米颗粒。根据核磁共振（NMR）和小角中子散射（SANS）结果，大部分聚甲基丙烯酸甲酯（PMMA）吸附在颗粒的核壳界面处。一小部分较短的PMMA可能附着在PMA链的外部。通过NMR和SANS时间分辨实验研究了苯和氯仿的吸收动力学及平衡。PS核中的扩散前沿非常窄，但在PMMA层中相当宽，这表明PMMA的状态不太紧密。根据SANS结果，扩散动力学几乎与PMMA层的厚度无关。与之相反，由SANS和NMR反映的吸收容量随颗粒中PMMA含量的增加而显著增加。溶解化合物的最大量取决于其与PMMA的正相互作用（由χ参数表示），但受到溶胀的PMMA与D₂O之间不断增加的界面张力的限制。根据这一结论，饱和苯的颗粒只能通过将一部分苯排入周围介质来吸收氯仿，反之亦然。从10 g PMMA/L（原始胶束重量的10倍）开始，当用良溶剂溶胀时，颗粒变得不稳定。
