Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy.
Phys Rev Lett. 2009 Dec 4;103(23):237801. doi: 10.1103/PhysRevLett.103.237801. Epub 2009 Nov 30.
We thoroughly investigate a simple model representative of the recently synthesized Janus particles, i.e., colloidal spherical particles whose surface is divided into two areas of different chemical composition. When the two surfaces are solvophilic and solvophobic, these particles constitute the simplest example of surfactants. The phase diagram includes a colloidal-poor (gas), colloidal-rich (liquid) demixing region, which is progressively suppressed by the insurgence of micelles, providing the first model in which micellization and phase separation are simultaneously observed. The coexistence curve is found to be negatively sloped in the temperature-pressure plane, suggesting that Janus particles can provide a colloidal system with anomalous thermodynamic behavior.
我们深入研究了一个简单的模型，该模型代表了最近合成的 Janus 粒子，即胶体球形粒子，其表面分为两个不同化学成分的区域。当两个表面都是亲溶剂和亲油的时，这些粒子构成了最简单的表面活性剂例子。相图包括胶体贫（气体）和胶体富（液体）的分相区域，这一区域逐渐被胶束的出现所抑制，提供了第一个同时观察到胶束化和相分离的模型。发现共存曲线在温度-压力平面上呈负斜率，这表明 Janus 粒子可以为胶体系统提供异常的热力学行为。
