报告人：Professor Yasumasa Nishiura

WPI Advanced Institute for Materials Research Tohoku University, Japan

题目：Frustrated nanoparticles and their metamorphosis

时间：2018年4月23日（星期一）下午14:00

地点：海韵园实验楼S105

Abstract:

Annealing of copolmers has become a tool of great importance to reconfigure nanoparticles. Herein, we present experimental results of annealing copolymer nanoparticles and a theoretical model to describe the morphological transformation from lamellae to onion. A good correspondence between experimental findings and predictions of the model is observed. The model based on finding the steepest direction of decent of an appropriate free energy leads to a set of Cahn-Hilliard equations that correctly describes the dynamical transformation from lamellae particles to onion and reverse onion-like particles, regardless of the nature of the annealing process. This universality makes possible to describe a variety of experimental conditions involving nanoparticles underlying a heating process. A notable advantage of the proposed approach is that it makes possible to selectively control the interaction between the confined copolymer and the surrounding media. This feature endows the model with great versatility to reproduce several combined effects of surfactants in diverse conditions, including cases with reverse affinities for the copolymersegments. A phase diagram to describe a variety of morphologies is presented. We employ relations between the temperature-dependent Flory-Huggins parameter and the width of the interfaces to account for changes in temperature due to the heating process. Simulation results correctly show how the transformation evolves as the temperature increases. This increment in temperature corresponds to progressively smaller values of the interfacial width. We anticipate that the proposed approach will facilitate the design and a more precise control of experiments involving various kinds of annealing processes. This is a joint work with E. Avalos, T. Teramoto, H. Komiyama, and H. Yabu.

联系人：许传炬教授

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