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기계적 물성이 제어된 Core-Shell 나노입자의 결정화를 통한연성 콜로이드 광결정 필름의 제조 및 인장감응 센서로 활용

Manufacturing of flexible colloidal photonic crystal films via crystallization of core-shell nanoparticles with controlled mechanical properties and applications as strain responsive sensors

  • 조영기 (Youngki Cho, 아주대학교 일반대학원)

초록/요약

Melt-shear assembly process has gained significant attention for its ability to fabricate densely packed three-dimensional colloidal photonic films with a core-shell structure of colloidal nanoparticles, exhibiting distinct properties. These films hold great potential as sensor materials due to their mechanochromic characteristics, which enable wavelength changes in response to various stimuli by diversifying the core and shell materials. In this study, the melt-shear process was employed to produce four colloidal photonic films with varying mechanical properties, utilizing the differences in their mechanical characteristics to create heterogeneous bimorph structures. The core material, polystyrene, and interlayer material, poly(methyl methacrylate), were synthesized using multistep starved-feed polymerization. The shell materials, poly(methyl acrylate), poly(hexyl methacrylate), poly(ethyl acrylate), and poly(2-ethylhexylacrylate), with different glass transition temperatures, were used to form a core-interlayer-shell(CIS) structure. Scanning electron microscopy (SEM) was employed to confirm the synthesis of nanoparticles and the formation of photonic crystals with diverse reflective colors. The synthesized nanoparticles were then processed into colloidal photonic films using the melt-shear assembly method. The optical properties of the fabricated films were examined using optical microscopy (BX-43, Olympus) and spectrophotometry (USB4000 VIS-NIR, Ocean Optics). Additionally, the strain-dependent optical signals were observed, revealing the mechanochromic properties of the three-dimensional colloidal photonic films. To evaluate the mechanical properties of the fabricated colloidal photonic films, a universal testing machine (UTM) was used. The films exhibited behavior similar to the shell matrix, displaying trends resembling the glass transition temperatures. Higher glass transition temperatures resulted in enhanced mechanical properties, while lower temperatures exhibited liquid-like behavior at room temperature. Leveraging the mechanical properties of the colloidal photonic films, structures were designed to control the extent of mechanochromic response to external strains, thereby regulating sensitivity to applied tension. Furthermore, by combining two photonic films with differing mechanical properties, heterostructured bimorphs were created, demonstrating distinct mechanochromic properties along the axis of tension. These structures not only enable intuitive detection of fine strains without the need for external equipment or energy consumption but also suggest the potential for strain sensing in a two-dimensional context.

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목차

1. 서론 (Introduction) 1
1.1. 인장 감응 센서 (Strain sensor) 1
1.2. 콜로이드 광결정 (Colloidal photonic crystal) 3
1.3. Melt-shear 조립을 통한 Core-Shell 나노입자기반 콜로이드 광결정 6
2. 실험 (Experimental) 11
2.1. 시약 및 재료 11
2.2. Multistep starved feed polymerization를 이용한 Core-Shell 나노입자 합성 11
2.2.1. Polystyrene core 중합 반응 13
2.2.2. Poly(methyl methacrylate)interlayer 중합 반응 13
2.2.3. Acrylate 계열 shell poymer 중합 반응 14
2.2.3.1. Poly(methyl acrylate)Shell 14
2.2.3.2. Poly(hexyl methacrylate)Shell 14
2.2.3.3. Poly(ethyl acrylate)Shell 14
2.2.3.4. Poly(2-ethyl hexyl acrylate)Shell 15
2.3. Melt-Shear 공정을 이용한 Core-Shell 나노입자 기반 콜로이드 광결정 필름 제작 15
2.4. Core-Shell 나노입자의 열 물성 분석 15
2.5. 콜로이드 광결정 필름의 기계적 특성 분석 16
2.6. 분석방법 16
3. 결과 및 토의 (Results and Discussion) 17
3.1. 합성된 Core-Shell 입자의 구조 및 열 물성 분석 17
3.2. 콜로이드 광결정 필름의 광학적 특성 및 열 물성에 따른 결정화도 분석 23
3.3. 인장에 따른 콜로이드 광결정 필름의 광학적 특성 변화 분석 29
3.4. 콜로이드 광결정 필름의 기계적 특성을 이용한 구조체 제작 및 광학적 특성 분석 33
3.5. 서로 다른 기계적 특성을 가진 콜로이드 광결정 필름을 조합한 이종상 구조의 역학 변색적 특성 분석 39
4. 결 론 (Conclusion) 45
References 47
Abstract 50

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