Linking the colloidal cluster morphology with the extended law of corresponding states

Authors: Néstor E. Valadez-Pérez1, Yun Liu2 and Ramón Castañeda-Priego1,2*



Particle aggregation is an obligatory step for the initiation of the phase separation or the large-scale formation of materials that exhibit a highly heterogeneous structure, such as gels, porous media and glasses. Nevertheless, even though the macroscopic structure of such materials depends strongly on the shape and size of the main building blocks, i.e., the basic units that constitute the supporting structure of any material, the physical mechanisms that lead to the rich cluster morphology is far from being completely understood. In this contribution, we show that it is possible to establish a connection between the cluster morphology in short-ranged attractive colloidal systems and the reduced second virial coefficient, B2. Overall, we observe that small clusters display the same morphology regardless the value of B2, whereas large clusters of two different colloidal systems have the same fractal dimension provided B2 is equal in both systems. Furthermore, weak attractions lead to open clusters, whereas strong attractions produce compact structures. Interestingly, this physical scenario holds at different thermodynamic conditions, namely, at the fluid state and the fluid-crystal coexistence, and close to the gas-liquid phase separation. Hence, our findings allow us to link reversible colloidal aggregation with the extended law of corresponding states.


1.   División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, Guanajuato, Mexico.

2.   The NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6100, USA


Summary of academic career

In 1998, Ramón Castañeda Priego received his bachelor's degree in physics (with honor) in the Department of Physics at the Universidad Veracruzana. From 1998 to 2000 he worked in the Physics Department of CINVESTAV - IPN where he received a master degree in Physics. From 2001 to 2003 he worked at the same institution where he received a Ph.D. degree in 2003. In the same year, he moved to the University of Konstanz, Germany, for a Post-Doctoral stint with Prof. Rudolf Klein and Prof. Hans-Hennig von Grünberg. From 2004 to present he is a full professor at the Division of Sciences and Engineering (before Institute of Physics) of the University of Guanajuato, Mexico. He has been honored with several awards and distinctions has Marcos Moshinsky fellowship, the Alexander von Humboldt research fellowship for experienced researchers and the Mexican Academy of Science research prize for young scientists in Hard Sciences (Physics, Mathematics, Chemistry and Astronomy). He is a member of National System of Researchers, current level 3. He has given at least 50 invited talks at international conferences and meetings and has published more than 60 papers in refereed journals. Your research interest is the Thermodynamics, structural properties, transport phenomena, dynamical arrest and self-assembly of many-body systems (colloids, polyelectrolytes, polymers, DNA molecules, among others). Advanced numerical algorithms, parallel computer simulation methods and experimental techniques (scattering methods, rheology, confocal videomicroscopy, optical trapping, etc.) for the research of soft condensed matter physics.