Direct observation of the dynamics of segmental motion for polymer chain isolated on the solid interface

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20537
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0501:Physical chemistry, functional solid state chemistry, organic chemistry, polymers, organic materials, biomolecular chemistry, and related fields
• Research Institution: Kyushu University
• Principal Investigator: Morimitsu Yuma 九州大学, 工学研究院, 助教 (60961696)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 一本鎖 / 直接観察 / セグメント運動 / 固体界面 / 複合材料 / 高分子 / 構造 / 物性

Outline of Final Research Achievements

In this study, we aimed to visualize the thermal motion of polystyrene (PS) adsorbed chains using an atomic force microscope (AFM). PS isolated chains dispersed on a silicon step substrate were prepared by spin-casting an ultra-dilute PS solution onto the substrate. The time-dependent change in the height image of the PS isolated chain was evaluated based on the tapping mode of the AFM. Height fluctuations were observed on the isolated chain. At each position, an autocorrelation function (ACF) was created from the time-dependent change in height, and the relaxation time was extracted to create a relaxation time map. Measurements were made at various temperatures, and the temperature dependence of the relaxation time map was obtained. As a result, it was found that not only the thermal motion of the loops but also phenomena such as desorption and adsorption could be observed.

Free Research Field

高分子・繊維材料

Academic Significance and Societal Importance of the Research Achievements

高分子の熱運動の理解は、材料物性・機能性の正確な設計・制御に繋がる。特に、主鎖セグメントの解放 (or凍結) によって達成されるガラス転移は重要な物性の一つである。これまで多くの概念が提唱されてきたが、その描像には未解明な点が多い。一方、固体上に吸着した分子鎖はループおよびトレインと呼ばれる形態を取る。ここでループおよびトレインは、それぞれ基板に接触点を持つおよび持たないセグメントを表す。今回直接観察に成功した、ループの熱運動性は、本質的にセグメント運動に近い運動であると考えられる。すなわち、今回の結果は、高分子のガラス転移の分子描像に大きな影響を与えると期待でき、学術的・社会的意義は大きい。