Date/Time
Date(s) - 12/09/2012
3:20 pm - 4:20 pm

Title: Connecting the Dots: Transition Pathways Between Ordered Phases of Block Copolymers

Speaker: Dr. An-Chang Shi

Institute: McMaster University

Location: ABB 102

Description:

Phase transitions are ubiquitous in nature. Understanding the kinetic pathways of phase transitions has been a challenging problem in physics and physical chemistry. From a thermodynamics point of view, the kinetics of phase transitions is dictated by the characteristics of the free energy landscape. A first step to explore the free energy landscape is a linear stability analysis, which can be used to determine the metastable region. When a system is in a metastable region, phase transitions proceed via nucleation and growth process. The nucleation of a droplet of stable phase from a metastable phase follows specific paths, the minimum energy paths (MEPs), on the free energy landscape. The MEP connecting two ordered phases can be computed using a recently developed string method. The shape, size and free energy barrier of critical nuclei are obtained from the MEP, providing information about the emergence of a stable ordered phase from a metastable phase. Examples of phase transition pathways are presented for block copolymer phases.