論文 / 著書情報
Article / Book Information
題目(和文)

ブロックコポリマー系熱可塑性エラストマーのモルフォロジーおよびナノメカニカル特性評価

Title(English)

Morphological and Nanomechanical Characterization of Block
Copolymer-Based Thermoplastic Elastomers

著者(和文)

劉浩男

Author(English)

Haonan Liu

出典(和文)

学位:博士(工学),学位授与機関:東京工業大学,
報告番号:甲第11801号,
授与年月日:2022年3月26日,
学位の種別:課程博士,
審査員:中嶋 健,福島 孝典,原 正彦,古屋 秀峰,澤田 敏樹

Citation(English)

Degree:Doctor (Engineering),Conferring organization: Tokyo Institute of Technology,
Report number:甲第11801号,Conferred date:2022/3/26,
Degree Type:Course doctor,Examiner:,,,,

学位種別(和文)博士論文Category(English)

Doctoral Thesis

種別(和文)

論文要旨

Type(English)

Summary

Powered by T2R2 (Tokyo Institute Research Repository)

（博士課程）Doctoral Program論 文 要 旨ＴＨＥＳＩＳ ＳＵＭＭＡＲＹ

系・コース：
Department of, Graduate major in

応用化学
応用化学

学生氏名：
Student’s Name系
コース

劉 浩男

申請学位（専攻分野）：

博士

Academic Degree Requested

Doctor of

指導教員（主）：Academic Supervisor(main)

指導教員（副）：Academic Supervisor(sub)

（工学）
中嶋 健
福島 孝典

要旨（英文 800 語程度）
Thesis Summary （approx.800 English Words ）Thermoplastic elastomers (TPEs) retain permanent deformation after elongation, preventing them from replacing rubber asan environmentally friendly material. To address TPE's vulnerability, in this thesis, an in situ atomic force microscopy (AFM)
is used to characterize the evolution of TPEs' microstructure and micromechanical properties before, during, and afterstretching. A finite element analysis (FEA) is then developed and implemented to visualize the local behavior of TPE at thenanoscale. Experiments and data analysis show that solving the hard-domain splitting problem in TPE's microphaseseparated structure is crucial to increasing its strength.
Chapter 1, "Introduction A: Thermoplastic Elastomers", gives an overview of the TPEs' microphase-separated structure of thehard domain and soft matrix, as well as their mechanical properties, which combine flexibility and toughness like crosslinked
rubber. In TPE materials, however, because the hard domain acts as a physical crosslinking point, the crosslinking point's
binding force is weaker than that of chemically crosslinked rubber, and stress relaxation and residual strain are considered
inferior. The importance of elucidating the macroscopic and microscopic structure-property relationships for TPE materials
under deformation is discussed to provide design guidelines for TPE materials that can replace cross-linked rubbers. It is also
discussed that, while molecular dynamics (MD) simulations predict hard domain behavior during deformation, experimental
techniques to validate the predictions are lacking.
Chapter 2, "Introduction B: Atomic Force Microscopy for Polymer Science", discusses the principle of simultaneous
measurement of structure and properties of polymeric materials by a nano-palpation technique based on AFM, as well as theeffect of deformation of the AFM tip on the sample. It also presents a typical Johnson-Kendall-Robert (JKR) contact
theoretical model for analyzing the load-deformation curve produced when an AFM probe is deformed into a sample. Thein-situ nano-palpation AFM is also developed and described, which allows in-situ observation of nanostructure and physicalproperties of specimens under deformation, as well as investigation of stress relaxation and residual strain in TPE materials.
Chapter 3, "Dynamic Stress Network in the TPE", investigates the macroscopic stress relaxation phenomenon of TPE
materials under constant strain using a block copolymer TPE, styrene-ethylene-butylene-styrene (SEBS). At 50% elongation,in situ AFM is used to investigate the microstructure and properties of SEBS. It has been confirmed that when the soft matrix
is elongated, stress chains connecting the hard domains form in the soft matrix, and that the soft matrix modulus decreases
while the number of hard domains increases in the early stages of the relaxation process, before stabilizing in the later stages.
Furthermore, by focusing on a specific local region, the formation of hard domains, the emergence of new stress chains, andthe splitting of hard domains, i.e., the existence of a dynamic stress network, has been clarified. The topology of the polymer
is permanently changed by the dynamic stress network, implying that it is caused by stress relaxation phenomena.
Chapter 4, "Nanoscale Strain-Stress Mapping for the TPE", develops an FEA program for AFM images to better understandthe relationship between the "dynamic stress network" and the property changes of TPE materials. In this program, the harddomain distributed in the AFM deformation image is extracted as a set of discrete points and divided into each image byDelaunay triangulation. The strain in each triangle region is calculated during the relaxation process and combined with theAFM modulus image, the local strain and local stress can be discussed. In the early stage of the relaxation process, severe
contraction occurs inside the material along the tensile direction and stress concentration is observed. In the later stage,
unlike the early stage, the average strain in the tensile direction becomes close to zero, the region of stress concentration
disappears, and the stress is uniformly distributed over a small area, describing the visualization of the stress relaxation
behavior of TPE materials at a microscopic level.
Chapter 5, "Heterogeneously Formation of the Stress Network in the TPE", observes the microstructure and physicalproperties of the initial elongation process of the TPE material from unelongated to about 45% elongation by in situ
nano-palpation AFM. The micro-elastic modulus and macro-stress were measured. Since both micro-elastic modulus andmacro-stress show a non-linear correlation with strain, the FEA method will be used to study them in detail. Initially, almost
all regions deformed regularly, but at the cost of stress concentration in some regions. As the strain increases, non-uniform
deformation due to accumulated stresses begins. Finally, all the domains are simultaneously undergoing negative deformation
with stress relaxation. The number of domains decreases and then increases during this process, which establishes
consistency with the MD simulation prediction.
Chapter 6, "AFM Characterization of Triptycene-Appended Polymers", investigates triptycene-appended polymers by AFM.
The triptycene units in the side chains of the block copolymer and both terminals of the polymer are described as a special
aggregation structure that improves the mechanical properties of the original polymer.
Chapter 7, "Summary and Open Questions", summarizes the contents of this thesis and describes the prospects.
備考 : 論文要旨は、和文 2000 字と英文 300 語を 1 部ずつ提出するか、もしくは英文 800 語を 1 部提出してください。
Note : Thesis Summary should be submitted in either a copy of2000 Japanese Characters and 300 Words (Engｌish) or 1copy of 800

Words (English).
注意：論文要旨は、東工大リサーチリポジトリ（T2R2）にてインターネット公表されますので、公表可能な範囲の内容で作成してください。
Attention: Thesis Summary will be published on Tokyo Tech Research Repository

Website (T2R2).