Ramirez-Hernandez received his PhD in physics from the Facultad de Ciencias (Universidad Autonoma del Estado de Morelos, Mexico), under the supervision of Dr. Francois Leyvraz (ICF-UNAM) and Dr. Hernan Larralde (ICF-UNAM). During his graduate studies he was working on the statistical equilibrium of systems governed by long-range interactions. These kinds of systems typically show in-equivalence of ensembles; in particular, within the microcanonical ensemble some systems can show negative specific heat. An interesting result obtained by his research is that the thermal contact of two systems with negative specific heat under same thermodynamical condition will lead to an increase in the entropy, therefore violating the Zeroth Law of Thermodynamics.
Ramirez-Hernandez continued his research career as a postdoctoral associate in Professor Juan de Pablo’s group at University of Wisconsin-Madison. During this stage, his research was focused on the statistical physics of soft condensed matter, with particular emphasis on self- and directed assembly of block copolymers and the rheology of these materials. His research has been based on the use of computational modelling and theory. An important point to highlight is his strong collaboration with experimental groups; thus, his research is enhanced by the synergy between experimental work, simulations, and theory.
Soft matter is dominated by the relatively weak interactions between their constituent entities. They are easily deformed and the energy scale of the interactions is in the order of magnitude of the thermal energy. These materials self-assemble into structures whose length scale is in the mesoscopic regime. Soft materials could exhibit a range of thermophysical properties that are intermediate between those of liquids and crystalline solids. It is because these unique properties that soft materials have attracted abiding interest not only from a fundamental point of view but also for technological applications. Examples of these materials are: colloids, polymers, surfactants, liquid crystals, virus, etc.
In recent years, the directed assembly of block copolymer thin films has attracted interest for fabrication of dense arrays of nanostructures. Chemically patterned surfaces can control the orientation, dimensions and shapes of block copolymer domains. The understanding of the impact of chemical patterns on block copolymer morphologies as well as the rheological properties of these materials and the underlying physics give insight into the nanofabrication of complex nanostructures useful in advanced technologies.
Using computer simulations and theory we study the statistical physics of Soft Condensed Matter, with particular emphasis on self- and directed assembly of block copolymers, rheology of polymer melts and nanocomposites. Their research is based on the use of coarse-grained models to address large scale and time properties of these materials.
Wright, Daniel B., et al. "Enzyme-Induced Kinetic Control of Peptide–Polymer Micelle Morphology." ACS Macro Letters 8 (2019): 676-681.
Hur, Su-Mi, et al. "Defect annihilation pathways in directed assembly of lamellar block copolymer thin films." ACS nano 12.10 (2018): 9974-9981.
Ramírez-Hernández, Abelardo, et al. "A detailed examination of the topological constraints of lamellae-forming block copolymers." Macromolecules 51.5 (2018): 2110-2124.
Directly observing micelle fusion and growth in solution by liquid-cell transmission electron microscopy
Parent, Lucas R., et al. "Directly observing micelle fusion and growth in solution by liquid-cell transmission electron microscopy." Journal of the American Chemical Society 139.47 (2017): 17140-17151.
Li, Xiao, et al. "Mesoscale martensitic transformation in single crystals of topological defects." Proceedings of the National Academy of Sciences 114.38 (2017): 10011-10016.
Rahimi, Mohammad, et al. "Segregation of liquid crystal mixtures in topological defects." Nature communications 8 (2017): 15064.
Ramírez-Hernández, Abelardo, et al. "Demixing by a nematic mean field: coarse-grained simulations of liquid crystalline polymers." Polymers 9.3 (2017): 88.
A multi-chain polymer slip-spring model with fluctuating number of entanglements: Density fluctuations, confinement, and phase separation
Ramírez-Hernández, Abelardo, et al. "A multi-chain polymer slip-spring model with fluctuating number of entanglements: Density fluctuations, confinement, and phase separation." The Journal of chemical physics 146.1 (2017): 014903.
Ramezani-Dakhel, Hadi, et al. "Understanding Atomic-Scale Behavior of Liquid Crystals at Aqueous Interfaces." Journal of chemical theory and computation 13.1 (2016): 237-244.
Hur, SM; Thapar, V; Ramirez-Hernandez, A; Khaira, G; Segal-Peretz, T; Rincon-Delgadillo, PA; Li, WH; Muller, M; Nealey, PF; de Pablo, JJ. Molecular pathways for defect annihilation in directed self-assembly. PNAS. 2015. Vol. 112, Pg. 14144–14149.