Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai-400085, India.
Langmuir. 2012 Jan 24;28(3):1914-23. doi: 10.1021/la204161d. Epub 2012 Jan 12.
Micrometric grains of anisotropic morphology have been achieved by evaporation-induced self-assembly of silica nanoparticles. The roles of polymer concentration and its molecular weight in controlling the buckling behavior of drying droplets during assembly have been investigated. Buckled doughnut grains have been observed in the case of only silica colloid. Such buckling of the drying droplet could be arrested by attaching poly(ethylene glycol) on the silica surface. The nature of buckling in the case of only silica as well as modified silica colloids has been explained in terms of theory of homogeneous elastic shell under capillary pressure. However, it has been observed that colloids, modified by polymer with relatively large molecular weight, gives rise to buckyball-type grains at higher concentration and could not be explained by the above theory. It has been demonstrated that the shell formed during drying of colloidal droplet in the presence of polymer becomes inhomogeneous due to the presence of soft polymer rich zones on the shell that act as buckling centers, resulting in buckyball-type grains.
通过二氧化硅纳米粒子的蒸发诱导自组装，实现了各向异性形态的微观颗粒。研究了聚合物浓度及其分子量在控制组装过程中干燥液滴的翘曲行为中的作用。仅在二氧化硅胶体的情况下观察到了有褶皱的甜甜圈状颗粒。通过在二氧化硅表面附着聚乙二醇，可以阻止干燥液滴的这种翘曲。根据毛细压力下均匀弹性壳的理论，解释了仅在二氧化硅以及改性二氧化硅胶体情况下的翘曲性质。然而，观察到的是，用相对高分子量的聚合物改性的胶体在较高浓度下会产生类巴基球型颗粒，而不能用上述理论来解释。已经证明，在聚合物存在下胶体液滴干燥过程中形成的壳由于壳上存在柔软的富含聚合物的区域而变得不均匀，这些区域充当了翘曲中心，导致了类巴基球型颗粒的形成。
