Title Page

Abstract

요약

Contents

Chapter 1: General Introduction 20

1.1. Background and literature review 20

1.1.1. Ring-opening metathesis polymerization of norbornene-based monomers 20

1.1.2. Ruthenium-based catalysts 24

1.1.3. Self-healing concept 27

1.1.4. Fundamental theory on cure kinetics 30

1.1.5. Functionalization of carbon nanotubes for polymer-composite preparation 35

1.2. Research motivations 37

1.3. Thesis organization 38

1.4. References 39

Chapter 2: Effect of Grubbs' Catalysts on Cure Kinetics of Endo-Dicyclopentadiene 46

2.1. Abstract 46

2.2. Introduction 46

2.3. Experimental 49

2.3.1. Materials 49

2.3.2. Recrystallization and dissolution of Grubbs' catalysts 49

2.3.3. Sample preparation and DSC measurement 52

2.3.4. Curing reaction kinetics 53

2.4. Results and discussion 55

2.4.1. Dynamic curing process 55

2.4.2. Model-free isoconversional kinetics 59

2.4.3. Model-fitting kinetics 64

2.5. Conclusions 67

2.6. References 68

Chapter 3: Curing Kinetics and Mechanical Properties of Endo-Dicyclopentadiene Synthesized Using Different Grubbs' Catalysts 71

3.1. Abstract 71

3.2. Introduction 71

3.3. Fundamental theory on the kinetics of the curing reaction 74

3.3.1. Model-free isoconversional method 75

3.3.2. Model-fitting method 76

3.4. Experimental section 77

3.4.1. Materials 77

3.4.2. Uncured sample preparation and DSC measurement 77

3.4.3. Cured sample preparation 78

3.4.4. Swelling behavior 78

3.4.5. Tensile test 78

3.4.6. Dynamic mechanical analysis 79

3.5. Results and discussion 79

3.5.1. Thermochemical analysis 79

3.5.2. Evaluation of swelling behavior and tensile properties 97

3.5.3. Viscoelastic behavior 101

3.6. Conclusions 103

3.7. References 104

Chapter 4: Cure Kinetics and Physical Properties of Poly(Dicyclopentadiene/5-Ethylidene-2-Norbornene) Initiated by Different Grubbs' Catalysts 109

4.1. Abstract 109

4.2. Introduction 109

4.3. Experimental 112

4.3.1. Materials 112

4.3.2. Preparation of uncured samples and DSC measurements 113

4.3.3. Fabrication of cured samples 113

4.3.4. Gel fraction and swelling measurements 113

4.3.5. Tensile tests and SEM observation 114

4.3.6. Dynamic mechanical analysis 114

4.3.7. Thermogravimetric analysis 115

4.4. Results and discussion 115

4.4.1. Thermochemical analysis 115

4.4.2. Gel fraction and swelling measurements 124

4.4.3. Tensile properties 126

4.4.4. Thermo-mechanical properties 130

4.4.5. Thermogravimetric analysis 137

4.5. Conclusions 137

4.6. References 138

Chapter 5: Evaluation of 5-Ethylidene-2-Norbornene with An Adhesion Promoter for Self-Healing Applications 142

5.1. Abstract 142

5.2. Introduction 142

5.3. Experimental section 148

5.3.1. Materials 148

5.3.2. Preparation of uncured healing agent solution 148

5.3.3. Preparation of lap shear samples 148

5.3.4. Preparation of microcapsules 149

5.3.5. Healing performance evaluation 149

5.3.6. Characterization 150

5.4. Results and discussion 150

5.4.1. Cure kinetics 150

5.4.2. Lap shear strength measurements 156

5.4.3. Autonomous self-healing 159

5.5. Conclusions 169

5.6. References 170

Chapter 6: Reinforcement of Norbornene-Based Nanocomposites with Norbornene Functionalized Multi-Walled Carbon Nanotubes 174

6.1. Abstract 174

6.2. Introduction 175

6.3. Experimental section 178

6.3.1. Materials 178

6.3.2. Acid functionalization of MWNTs 178

6.3.3. Norbornene functionalization of MWNTs 179

6.3.4. Preparation of nanocomposites 179

6.3.5. Characterization 180

6.4. Results and discussion 180

6.4.1. Synthesis and characterization of nMWNTs 180

6.4.2. Dispersion stability of pMWNTs and nMWNTs 186

6.4.3. Cure kinetics of nMWNT/DCPD/NCA solutions 188

6.4.4. Swelling behaviors of nMWNT/poly(DCPD/NCA) nanocomposites 193

6.4.5. Tensile properties of MWNT/poly(DCPD/NCA) nanocomposites 193

6.4.6. Dynamic mechanical behavior of MWNT/poly(DCPD/NCA) nanocomposites 199

6.5. Conclusions 202

6.6. References 203

Chapter 7: Norbornene functionalized multi-walled carbon nanotubes for improving the dispersibility in solvents and reinforcing poly(5-ethylidene-2-norbornene) nanocomposites 208

7.1. Abstract 208

7.2. Introduction 209

7.3. Experimental section 211

7.3.1. Materials 211

7.3.2. Synthesis of norbornene functionalized MWNTs 212

7.3.3. Fabrication of MWNT/poly(ENB) nancomposite films 212

7.3.4. Characterization 213

7.4. Results and discussion 214

7.4.1. Functionalization and characterization of MWNTs 214

7.4.2. Dispersibility of MWNTs in solvents 220

7.4.3. Fabrication of nMWNT/poly(ENB) nanocomposites 223

7.4.4. Tensile properties of nMWNT/poly(ENB) nanocomposites 225

7.4.5. Dynamic mechanical properties of nMWNT/poly(ENB) nanocomposites 230

7.5. Conclusions 233

7.6. References 233

7.7. Supporting information 239

Chapter 8: General Conclusions 243

8.1. General conclusions 243

8.2. Recommendations for future research 245

Table 2-1. Cure models in model-fitting method 54

Table 2-2. Onset and peak temperature of cure, Tonset and Tp, temperature range from...(이미지참조) 57

Table 2-3. Results of multiple linear regression analysis for the 1st generation catalyst...(이미지참조) 65

Table 3-1. Typical parameters for the isothermal curing reaction and the subsequent... 84

Table 3-2. Calculated kinetic parameters for the nth-order and SB models 91

Table 3-3. Critical conversion (αc) and diffusion constant (C) values for the diffusion...(이미지참조) 95

Table 3-4. Results of tensile tests for poly-DCPD produced with the 1st and 2nd generation...(이미지참조) 99

Table 4-1. Onset and peak cure temperatures, Tonset and Tp, and total enthalpy, △HR, for...(이미지참조) 117

Table 4-2. Summary of tensile test results for cured DCPD/ENB blends 128

Table 4-3. Summary of DMA results for DCPD/ENB blends 133

Table 4-4. Thermogravimetric results for the cured blends 136

Table 5-1. Thermal behavior for ENB/MNC blends with different MNC loadings 152

Table 6-1. Peak cure temperature Tp, total enthalpy △HR, and activation energy △E of...(이미지참조) 191

Table 6-2. Tensile properties of poly(DCPD/NCA) nanocomposites with pMWNTs and... 196

Table 6-3. DMA results of poly(DCPD/NCA) nanocomposites with pMWNTs and... 201

Table 7-1. Tensile properties of neat poly(ENB) and poly(ENB) nanocomposites with... 226

Table 7-2. DMA results of neat poly(ENB) and poly(ENB) nanocomposites with... 232

Figure 1-1. A general mechanism of a typical ROMP reaction 21

Figure 1-2. ROMP schemes of DCPD and ENB 23

Figure 1-3. Commercially available ruthenium-based catalysts for ROMP 26

Figure 1-4. Microcapsule-based self-healing system with encapsulated healing agent and... 29

Figure 1-5. Characteristic reaction profiles of conversion (α) vs. time (t) for (1)... 34

Figure 2-1. Ruthenium-based 1st and 2nd generation Grubbs' catalysts initiating the...(이미지참조) 47

Figure 2-2. SEM images of as-received and recrystallized for the 1st and 2nd generation...(이미지참조) 50

Figure 2-3. Catalyst dissolution of as-received and recrystallized catalysts 51

Figure 2-4. DSC scans at different heating rates for endo-DCPD with (a) the 1st...(이미지참조) 56

Figure 2-5. Fractional conversion vs. temperature for the 1st generation and 2nd generation(이미지참조)... 58

Figure 2-6. Model-free results for the activation energy (E) and ln[A×f(α)] at each... 61

Figure 2-7. Model-free predictions and experimental data for (a) the 1st generation and (b)...(이미지참조) 62

Figure 2-8. Model fits of DSC data for endo-DCPD with the 1st generation catalyst(이미지참조) 66

Figure 3-1. Reaction scheme of ROMP for endo-DCPD and the 1st and 2nd generation...(이미지참조) 73

Figure 3-2. The isothermal DSC scans of endo-DCPD with (a) the 1st generation and (b)...(이미지참조) 80

Figure 3-3. Dynamic DSC scans following the isothermal cure of endo-DCPD with (a)... 81

Figure 3-4. Fractional conversion versus time for endo-DCPD with (a) the 1st generation...(이미지참조) 82

Figure 3-5. Isothermal conversion rate as a function of the fractional conversion for... 83

Figure 3-6. Activation energy as a function of the fractional conversion for endo-DCPD... 87

Figure 3-7. Arrhenius plots of ln k versus 1/T for both catalyst systems 92

Figure 3-8. Comparison of the predictions from Eqs 93

Figure 3-9. Diffusion factor as a function of the fractional conversion for endo-DCPD... 94

Figure 3-10. Comparison of the predictions from Eqs 96

Figure 3-11. Stress-strain curves for poly-DCPD initiated by the 1st and 2nd generation...(이미지참조) 98

Figure 3-12. SEM images of the fracture surface of tensile specimens with (a) the 1st...(이미지참조) 100

Figure 3-13. Storage modulus (E') and damping factor (tan δ) as a function of temperature... 102

Figure 4-1. (a) ROMP schemes of DCPD and ENB and (b) chemical structures of the 1st...(이미지참조) 111

Figure 4-2. Typical DSC thermograms of DCPD/ENB blends with (a) the 1st generation...(이미지참조) 116

Figure 4-3. Fractional conversion versus temperature for DCPD/ENB blends with (a) the... 120

Figure 4-4. Activation energy as a function of the fractional conversion for DCPD/ENB... 121

Figure 4-5. Gel fraction and swelling ratio of cured DCPD/ENB blends with the 1st and...(이미지참조) 125

Figure 4-6. Stress-strain curves of cured DCPD/ENB blends with (a) the 1st generation...(이미지참조) 127

Figure 4-7. SEM images of the fracture surface of tensile specimens with (a) the 1st...(이미지참조) 129

Figure 4-8. Storage modulus (E') and loss factor (tan δ) as a function of temperature for... 132

Figure 4-9. TGA thermographs of the cured blends with (a) the 1st generation and (b) the...(이미지참조) 135

Figure 5-1. Schematic mechanism of noncovalent interactions between the polymerized... 145

Figure 5-2. DSC curves for ENB/MNC blends with different MNC loadings 151

Figure 5-3. Activation energy versus fractional conversion for ENB/MNC blends with... 155

Figure 5-4. Lap shear strength of ENB with different MNC concentrations 157

Figure 5-5. Lap shear strength of healing agents as a function of cure temperature 158

Figure 5-6. Optical micrographs of microcapsules containing (a) ENB (400 rpm), (b)... 160

Figure 5-7. SEM micrographs 162

Figure 5-8. TGA curves of microcapsules containing ENB or ENB/MNC mixture and... 163

Figure 5-9. Effect of catalyst concentration on peak fracture load of self-activated healed... 165

Figure 5-10. Typical load-displacement curves from self-healing TDCB fracture tests 166

Figure 5-11. SEM images of fracture surface from self-healing samples containing (a)... 168

Figure 6-1. TGA traces of (a) pMWNTs, (b) MWNT-COOH, (c) nMWNTs, and (d)... 182

Figure 6-2. FTIR spectra of pMWNTs, MWNT-COOH, and nMWNTs 184

Figure 6-3. SEM images of (a) pMWNTs and (b) nMWNTs 185

Figure 6-4. (a) Photographs of i) pMWNTs in DCPD/NCA monomers, ii) nMWNTs in... 187

Figure 6-5. DSC cure traces of nMWNT/ DCPD/NCA solutions at a heating rate of 10°C/min 190

Figure 6-6. Swelling ratio of nMWNT/poly(DCPD/NCA) nanocomposites with different... 194

Figure 6-7. Representative stress-strain curves of poly(DCPD/NCA) nanocomposites... 195

Figure 6-8. SEM images of the fracture surface of poly(DCPD/NCA) nanocomposites... 197

Figure 6-9. Storage modulus and tan δ vs temperature for poly(DCPD/NCA)... 200

Figure 7-1. FTIR spectra of pMWNTs, MWNT-COOH, and nMWNTs 216

Figure 7-2. TGA curves of pMWNTs, MWNT-COOH, and nMWNTs 217

Figure 7-3. (a) XPS spectra and (b) XPS O1s spectra of pMWNTs, MWNT-COOH, and... 219

Figure 7-4. Photographs of nMWNTs dispersed in six solvents (after 3 days, 0.1 mg/mL) 221

Figure 7-5. UV-vis absorption spectra of nMWNTs in THF (Inset shows the absorbance at... 222

Figure 7-6. Representative stress-strain curves of neat poly(ENB) and poly(ENB)... 227

Figure 7-7. SEM images of the fracture surface of poly(ENB) nanocomposite films with... 228

Figure 7-8. Storage modulus and tan δ of neat poly(ENB) and poly(ENB)... 231

Figure 7-9. Photographs of nMWNTs dispersed in water, THF, acetone, ethanol,... 239

Figure 7-10. Photographs of pMWNTs dispersed in water, THF, acetone, and ethanol 240

Figure 7-11. Photographs of nMWNTs dispersed in THF, ENB/THF, poly(ENB)/THF... 241

Figure 7-12. DSC curves of ENB monomer with 2nd generation Grubbs' catalyst(이미지참조) 242

Scheme 6-1. Synthesis of acid functionalized MWNTs 181

Scheme 6-2. Synthesis of norbornene functionalized MWNTs 181

Scheme 6-3. Attachment of nMWNTs to polymer at (I) norbornene and (II) cyclopentene... 189

Scheme 7-1. Synthesis of norbornene functionalized MWNTs 215

Scheme 7-2. Possible polymerization mechanisms between nMWNTs and ENB 224

 류티늄 기반 촉매(Grubbs 촉매)의 발전과 함께 개환 복분해 중합(ring-opening metathesis polymerization, ROMP)에 의한 노르보넨 기반 고분자와 복합체의 제조에 대한 연구와 응용이 dicyclopentadiene(DCPD)와 5-ethylidene-2-norbornene(ENB)을 중심으로 광범위하게 진행되고 있다. 적절한 경화 사이클로 원하는 특성을 얻기 위해서 DCPD 의 경화속도에 미치는 Grubbs 촉매(1st 와 2nd generation)의 효과를 승온 및 등온 시차열량 분석법(differential scanning calorimetry, DSC)을 이용하여 조사하였다. 얻어진 DSC 데이터를 model-free isoconversion 법과 model-fitting 법으로 분석하여 속도 파라미터를 결정하였으며, 그 결과 두 종류의 Grubbs 촉매는 ROMP 반응과 활성화 에너지(activation energy, Eα)에서 큰 차이를 보였다. 또한 2nd generation Grubbs 촉매와 비교하였을 때 1st generation 이 가교구조를 형성하는데 더 효과적이며, 경화 후 poly(DCPD)에서도 더 높은 강성률, 강도 그리고 유리전이온도(glass transition temperature, Tg)를 나타내었다.

본 연구에서는 낮은 촉매 함량과 낮은 경화온도에서도 반응성이 우수한 노르보넨 기반 수지 시스템을 개발하기 위하여, 1st generation 과 2nd generation Grubbs 촉매를 이용하여 DCPD 와 ENB 의 비율을 달리하여 공중합시키고, 그들의 경화속도와 열적/기계적 특성을 조사하였다. DCPD 에 ENB 를 첨가함에 따라 촉매의 종류에 관계없이 반응속도가 빨라졌으며, 경화 후 고분자의 가교밀도와 열적/기계적 특성은 ENB 의 함량과 사용한 촉매의 양에 크게 영향을 받았다.

ROMP 반응은 자가치료 분야에도 널리 활용되고 있다. 따라서 본 연구에서는 DCPD 에 비해 반응성이 높고 융점이 낮은 ENB 를 자가치료제로 사용할 수 있는 가능성에 대한 연구를 진행하였다. Poly(ENB)와 에폭시 기질 사이의 접착강도를 향상시키기 위하여 접착 증진제(adhesion promoter)를 사용하였다. 그 결과 에폭시/ENB 마이크로캡슐 시스템은 낮은 촉매 함량(0.3 wt%)에서도 자가치료가 가능하였으며, 접착 증진제를 첨가함으로써 치료효율이 크게 향상되었다.

또한 노르보넨 기반 고분자 나노 복합체를 개발하기 위하여 다중벽탄소나노튜브(multi-walled carbon nanotube, MWNT)의 표면에 두 가지 다른 방법으로 노르보넨 그룹을 그래프팅하여 관능기화 하였다. 또한 노르보넨으로 관능기화된 MWNT 로 강화된 poly(DCPD)와 poly(ENB)는 각각 벌크 중합과 솔루션 캐스팅으로 나노 복합체를 제작하였다. 관능기화된 나노튜브는 노르보넨 기반 수지 내에서 매우 우수한 분산성을 나타내었으며, 이를 첨가하여 제조한 나노 복합체는 순수 고분자에 비해 훨씬 더 우수한 열적/기계적 특성을 나타내었다.