Computational Routes to Discover New Materials in Block Polymers
Akash Arora, Department of Chemical Engineering and Materials Science, University of Minnesota – Twin Cities, Minneapolis, USA
8th January, 2018, Monday 3-4PM in Seminar Hall, Dept of Chemical Engineering
Block polymers are a class of soft materials that self-assemble at mesoscopic length scales to form a wide variety of ordered structures, which are instrumental in the development of advance technologies such as nanostructured membranes and photonic crystals. In recent years, several experimental studies witnessed the formation of complex low-symmetry structures in sphere-forming block polymers. These structures, commonly referred to as Frank-Kasper (FK) phases, contain particles (micelles) of disparate sizes packed in a tetrahedral closed-packed arrangement with multiple local coordination environments. Typically found in multicomponent materials such as metallic alloys and surfactant solutions, the emergence of such complex structures in single-component block polymers has generated renewed in-terest in the fundamental phase behavior of these materials.
In this talk, I will discuss our recent efforts in developing predictive computational ap-proaches to simulate and determine the stability of complex phases in block polymers using self-consistent field theory (SCFT) (www.pscf.cems.edu). The SCFT framework involves iter-atively solving a set of highly non-linear equations, the convergence of which depends on the guess structure used to begin the iteration procedure. We developed a physically informed and robust approach that uses information from experiments to generate appropriate guess structures and perform successful SCFT calculations. Using this approach, we observed that several FK phases exist on the free energy surface of diblock copolymers. Importantly, the associated free energies differ only marginally (10−3kBT), leading to a very rugged free energy surface with many local minima that may be accessible via different nucleation pathways. I will discuss the significance of these results in the context of two new FK phases discovered recently in poly(isoprene)-b-poly(lactide) diblock copolymers. Additionally, I will discuss our work on studying the finite size effects in lattice Monte-Carlo simulations of diblock copolymers, which enabled us to accurately determine the domain spacing of a lamellar structure, the most common morphology for making computer chips.
Biographical Sketch
Akash Arora is currently a PhD candidate in the Chemical Engineering program at the University of Minnesota, where he is advised by Professors Kevin D. Dorfman and Frank S. Bates.He received his Bachelors degree in Chemical Engineering from BITS-Pilani University (Goa Campus) in 2010. Following that, he went to pursue a Masters program at National ChemicalLaboratory - Pune, specializing in Advanced Modeling and Simulation in Chemical Engineering and Science. There, he worked on developing finite element models to study the spin-coating flow of non-Newtonian fluids. His current research involves studying thermodynamics of block polymers using theoretical and computational methods.