School of Chemistry, University of Sydney, NSW 2006, Australia.
Soft Matter. 2017 Oct 11;13(39):7141-7153. doi: 10.1039/c7sm01401e.
We investigate the fluid structure and self-assembly of a system of Janus dumbbells by means of aggregation-volume-bias Monte Carlo simulations and Simulated Annealing techniques. In our approach, Janus dumbbells model asymmetric colloidal particles constituted by two tangent (touching) spheres (labelled as h and s) of different sizes and interaction properties: specifically, the h spheres interact with all other spheres belonging to different dumbbells via hard-sphere potentials, whereas two s spheres interact via a square-well potential. By introducing a parameter α ∈ [0,2] that controls the size ratio between the h and s spheres, we are able to investigate the overall phase behaviour of Janus dumbbells as a function of α. In a previous paper (O'Toole et al., Soft Matter, 2017, 13, 803) we focused on the region where the s sphere is larger than the h sphere (α > 1), documenting the presence of a variety of phase behaviours. Here we investigate a different regime of size ratios, predominantly where the hard sphere is larger than (or comparable to) the attractive one. Under these conditions, we observe the onset of many different self-assembled super-structures. Depending on the specific value of α we document the presence of spherical clusters (micelles) progressively evolving into more exotic structures including platelets, filaments, networks and percolating fluids, sponge structures and lamellar phases. We find no evidence of a gas-liquid phase separation for α ≤ 1.1, since under these conditions it is pre-empted by the development of self-assembled phases.
我们通过聚合体-体积-偏差蒙特卡罗模拟和模拟退火技术研究了 Janus 哑铃体系的流体结构和自组装。在我们的方法中，Janus 哑铃模型由两个相切（接触）的不同大小和相互作用特性的球体（标记为 h 和 s）组成的不对称胶体颗粒：具体来说，h 球体通过硬球势与属于不同哑铃的所有其他球体相互作用，而两个 s 球体通过方阱势相互作用。通过引入一个参数 α ∈ [0,2] 来控制 h 和 s 球体之间的大小比，我们能够研究 Janus 哑铃的整体相行为作为 α 的函数。在之前的一篇论文中（O'Toole 等人，《软物质》，2017 年，13，803），我们专注于 s 球体大于 h 球体的区域（α > 1），记录了各种相行为的存在。在这里，我们研究了大小比的不同区域，主要是硬球大于（或可与）有吸引力的球。在这些条件下，我们观察到许多不同的自组装超结构的出现。根据特定的 α 值，我们记录了球形簇（胶束）的存在逐渐演变成更奇特的结构，包括薄片、纤维、网络和渗透流体、海绵结构和层状相。我们没有发现 α ≤ 1.1 时存在气-液分相的证据，因为在这些条件下，自组装相的发展会抢先发生。
