2021/12/03(Fri) 10:30 -11:30 視訊會議室(圖書館) 3F, Video Conference Room(Library)
Title
Probing Coil-Globule Transition by Microrheology
Speaker
魏憲鴻教授 (國立成功大學化學工程學系) Prof. Hsien-Hung Wei (Department of Chemical Engineering, National Cheng Kung University)Abstract
When a polymer chain is subject to a change in its environment, it can undergo an abrupt conformational transition from the swollen coil state to the compact globule state. Much like vapor-liquid phase transition, this is the coil-globule transition (CGT), playing an essential role in many polymer synthesis and material preparation processes. Conventional methods for studying CGT such as dynamic light scattering and fluorescent correlation spectroscopy are very cumbersome because they are very sensitive to impurities and require extreme sample purification. Here we present a relatively easy but rather reliable approach to overcome this shortcoming. It is the microparticle-tracking microrheology (mPTM) technique in which we employ microparticles as probes to a polymer solution. Specifically, we measure the viscosity of a polymer solution from the diffusion coefficient of the probe particle. Because CGT can cause a change in the solution viscosity and this change can be related to a change in the hydrodynamic radius R of a polymer chain, we are able to identify the coil/globule state of a polymer chain by determining the scaling law for how R varies with the molecular weight M. The measured scaling laws for both coil and globule states are found in excellent agreement with those predicted by the classical Flory-deGennes theory, verifying the robustness of mPTM. The successful probing of CGT demonstrated in this work may stimulate the potential use of mPTM in studying a variety of polymer systems at micro/nanoscales.
Language
演講語言 (Language): in English
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