van de Laar T, Higler R, Schroën K, Sprakel J
Physical Chemistry and Soft Matter, Wageningen University, Wageningen, The Netherlands.
Laboratory of Food Process Engineering, Wageningen University, Wageningen, The Netherlands.
Sci Rep. 2016 Mar 4;6:22725. doi: 10.1038/srep22725.
In purely repulsive colloidal systems a glass transition can be reached by increasing the particle volume fraction beyond a certain threshold. The resulting glassy state is governed by configurational cages which confine particles and restrict their motion. A colloidal glass may also be formed by inducing attractive interactions between the particles. When attraction is turned on in a repulsive colloidal glass a re-entrant solidification ensues. Initially, the repulsive glass melts as free volume in the system increases. As the attraction strength is increased further, this weakened configurational glass gives way to an attractive glass in which motion is hindered by the formation of physical bonds between neighboring particles. In this paper, we study the transition from repulsive-to-attractive glasses using three-dimensional imaging at the single-particle level. We show how the onset of cage weakening and bond formation is signalled by subtle changes in local structure. We then demonstrate the discontinuous nature of the solid-solid transition, which is marked by a critical onset at a threshold bonding energy. Finally, we highlight how the interplay between bonding and caging leads to complex and heterogeneous dynamics at the microscale.
在纯排斥性胶体系统中，通过将颗粒体积分数增加到超过某个阈值，可以达到玻璃化转变。由此产生的玻璃态由构型笼控制，构型笼限制颗粒并限制其运动。胶体玻璃也可以通过诱导颗粒之间的吸引相互作用而形成。当在排斥性胶体玻璃中开启吸引力时，会发生再入凝固。最初，随着系统中自由体积的增加，排斥性玻璃会熔化。随着吸引力强度进一步增加，这种弱化的构型玻璃会被吸引性玻璃取代，在吸引性玻璃中，相邻颗粒之间形成物理键会阻碍运动。在本文中，我们使用单颗粒水平的三维成像研究从排斥性玻璃到吸引性玻璃的转变。我们展示了笼弱化和键形成的开始是如何通过局部结构的细微变化来表征的。然后，我们证明了固-固转变的不连续性，其特征是在阈值键能处有一个临界起始点。最后，我们强调了键合和笼化之间的相互作用如何导致微观尺度上复杂且不均匀的动力学。
