title page

Contents

List of abbreviation 19

Acknowledgments 21

ABSTRACT 23

Chapter 1. Introduction 29

1.1. Background and Motivation 30

1.2. General objectives 35

1.3. Specific objectives 35

1.4. Significance of the Study 36

1.5. Scope of the study 37

References: 38

Chapter 2. Review of Related literature 45

2.1. Thermoplastic Elastomer 46

2.2. Block copolymers 48

2.2.1. Basic aspect of block copolymers 48

2.2.2. Current Development of block copolymers 52

2.2.3. Dynamic Processing and Rheology 57

2.3. Polymer gels 58

2.3.1. Triblock copolymer gels 60

2.3.2. Other types of gels 61

2.3.2.1. Polyelectrolytes Gels 61

2.3.2.2. Chemical actuation of gels 62

2.3.2.3. Electrically actuated gels 63

2.3.3. Development of Nanocomposites polymer gels 64

References: 66

Chapter 3. Experimental 79

3.1 Materials 80

3.1.1. Polymer Material 80

3.1.2. Hydrocarbon mineral oil 80

3.1.3. Nanoparticles and conducting filler 81

3.1.3.1. Different types of nanographite 82

3.1.3.1.1. Expandable graphite 82

3.1.3.1.2. Exfoliated Graphite Nanoplatelet 85

3.1.3.1.3. Multiwalled carbon nanotubes 87

3.1.3.1.4. Carbon black 89

3.2. Thermoplastic Elastomer Gels Preparation 90

3.3. Nanocomposite Polymer Gels Preparation 90

3.4. Characterization Techniques and its principles 91

3.4.1. Viscoelastic measurement 91

3.4.1.1. Linear Viscoelastic Observation 94

3.4.1.2. Relaxation time 95

3.4.2. Thermal Analysis 96

3.4.2.1. Differential scanning calorimetry 97

3.4.2.2. TGA-DTA 97

3.4.3. Sol-gel Transition temperature 98

3.4.4. Structural development 98

3.4.4.1. X-ray diffraction(XRD) and small-angle X-ray diffraction (SAXS) 98

3.4.5. Morphological properties 100

3.4.5.1. Scanning Electron Microscope (SEM) 100

3.4.5.2. Transmission electron microscopy 101

3.4.5.3. Atomic force microscopy 102

3.4.6. Swelling Studies 104

3.4.7. Mechanical Properties 105

3.4.8. Electric Properties 105

3.4.8.1. Dielectric Strength 106

3.4.8.2. Permittivity/Dielectric constant 107

3.4.8.3. Conductivity and Resistivity 109

3.4.9. Actuator test-experiment 112

References: 113

Chapter 4. Physical Gelation Studies Of Poly[styrene-poly(Ethylene-Butylene)-Polystyrene] (SEBS) Thermoplastic Elastomer in Different Hydrocarbon Oils 116

4.1. Abstract 117

4.2. Introduction 118

4.3. Experimental 120

4.3.1. Materials and Gels Preparation 120

4.3.2. Viscoelastic behavior 120

4.3.3. Transition temperature 121

4.3.3.1. Sol-gel transition temperature 121

4.3.3.2. Glass transition temperature 122

4.3.4. Swelling studies 122

4.3.5. Structural and Morphological analyses 122

4.3.6. Mechanical properties 122

4.4. Results and Discussion 122

4.4.1. Dynamic Viscoelastic Behavior 122

4.4.1.1. Effect of temperature 122

4.4.1.2. Effect of frequency 126

4.4.1.3. Dynamic viscosity 131

4.4.2. Relaxation time 131

4.4.3. Swelling measurements 134

4.4.4. Thermal behavior 135

4.4.4.1. Sol-gel transition temperature 135

4.4.4.2. Glass Transition Temperature 137

4.4.5. Structural Analysis 140

4.4.5.1. Small-Angle X-ray Scattering 140

4.4.6. Morphological characteristics 146

4.4.6.1. Transmission electron microscopy 146

4.4.7. Model for thermoplastic elastomer gelation 148

4.4.8. Mechanical properties 151

4.5. Conclusions 154

References 155

Chapter 5. Development of New Multicomponent Nanocomposite Thermoplastic Elastomer Gels 160

5.1. Abstract 161

5.2. Introduction 162

5.3. Experimental 165

5.3.1. Materials 165

5.3.2. Preparation of multicomponent nanocomposite TPE gels 166

5.3.3. Characterization 166

5.4. Results and Discussion 166

5.4.1. Effect of temperature 166

5.4.1.1. Effect of temperature on nanoparticles 166

5.4.1.2. Effect of temperature on concentration 169

5.4.2. Effect of concentration on storage modulus 172

5.4.3. Maximum operating temperature 175

5.4.4. Effect of frequency 178

5.4.4.1. Effect of nanoparticles concentration 178

5.4.4.2. Effect of carbon black 178

5.4.4.3. Effect of different nanoparticles 179

5.4.4.4. Effect of temperature 182

5.4.5. Morphological properties 184

5.4.5.1. Transmission Electron Microscopy 184

5.4.5.2. Atomic Force Microscopy 189

5.4.5.3. X-ray diffraction 192

5.4.6. Thermal Behavior 197

5.4.6.1. Glass transition temperature 197

5.4.6.2. TGA-DTA 199

5.4.7. Mechanical Properties 204

5.5. Conclusions 211

References 212

Chapter 6. Electrical Properties of Nanocomposite Thermoplastic Elastomer Gels 220

6.1. Abstract 221

6.2. Introduction 222

6.3. Experimental 226

6.3.1. Materials and Composition 226

6.3.2. Characterization 227

6.4. Results and Discussion 228

6.4.1. Effect of filler loading 228

6.4.1.1. Dependence of dielectric constant 228

6.4.1.2. Effect of dielectric constant on frequency 237

6.4.2. Effect of frequency on dielectric constant 240

6.4.3. Effect of temperature on dielectric properties 242

6.4.4. Electrical conductivity and resistivity 248

6.4.4.1. Effect of filler loading 248

6.4.4.2. Dependence of Frequency 252

6.4.4.2.1. NCTPE gels 252

6.4.5. Dielectric breakdown 256

6.5. Conclusions 257

References: 258

Chapter 7. Nanocomposite Thermoplastic Elastomer Gels as Dielectric Elastomer 265

7.1. Abstract 266

7.2. Introduction 267

7.3. Theoretical Background 269

7.4. Experimental Procedure 275

7.4.1. Preparation of TPE gels and NCTPE gels 275

7.4.2. Preparation of test-sample 275

7.4.3. Preparation of Compliant Electrodes 276

7.4.4. Preparation of Dielectric Elastomer Diaphragm 278

7.4.5. Actuator Fabrication 281

7.4.6. Failure analysis 282

7.5. Results and Discussion 282

7.5.1. Actuator test 282

7.5.1.1. Thermoplastic Eastomer Gels as Dielectric elastomer 282

7.5.1.2. NCTPE gels as dielectric elastomer 284

7.5.2. Actuator Failure 286

7.6. Conclusions 289

References 289

Chapter 8. Conclusions and Future Plans 294

References: 300

International Journals (SCI) 301

International Conference Proceedings: 303

Table 3.1. Properties of different Paraffin oils 81

Table 3.2. Properties of expandable graphite 83

Table 3.3. Particle size 83

Table 4.1. Dynamic Mechanical Properties of the gels at ambient temperature (30˚C) 126

Table 4.2. Interdomain spacing (d) and micelle radius (r) of PS microdomain for all sample gels. 145

Table 4.3. SAXS intensities in Lin (counts) for all sample gels. 145

Table 5.1. Characteristics of thermal degradation 204

Table 6.1. Dielectric breakdown, kV 257

Figure 2.1. Morphology of block copolymer TPEs 47

Figure 2.2. A three-dimensional TEM image of the gyroid morphology in a microphase-ordered triblock copolymers. 54

Figure 2.3. (a) A TEM image of a TPE gel composed of 10wt% polystyrene-b-isoprene-b-styrene triblock copolymer and mineral oil. The OsO₄-stained polyisoprene appears dark, revealing the location of looped midblocks and... 56

Figure 2.4. Possible micellar chain topologies for (a) diblock (dangling end) and triblock copolymers chain in selective solvents (dangling end, bridge and loop). 61

Figure 3.1. Chemical Structure of Poly[styrene- b-(ethylene-co-butylene)-b-styrene] (SEBS) Triblock Copolymers 81

Figure 3.2. Structure of graphite 84

Figure 3.3. XRD patterns of EG1 and EG2 84

Figure 3.4. FE-SEM micrographs of a) EG1 and b) EG2 after sonication. 85

Figure 3.5. XRD pattern of (a) xGnP-15 (b) xGnP-1 86

Figure 3.6. FE-SEM micrograph of (a) xGnP-1 (b) xGnP-15, scale bar: 5 ㎛ 87

Figure 3.7. FE-SEM micrograph of MWCNTs. Bar scale: 200 ㎛ 88

Figure 3.8. XRD pattern of MWCNTs 88

Figure 3.9. XRD pattern of pureblack 205 carbon 89

Figure 3.10. FE-SEM micrograph of aggregates of pureblack 205 carbon 90

Figure 3.11. Schematic parallel plates. 92

Figure 3.12. Schematic illustration of a small cube volume under shear 93

Figure 3.13. Schematic diagram for atomic force microscopy 103

Figure 3.14. Schematic illustration of different types of electrode method used for the determination of permittivity of the materials. 109

Figure 3.15. Diagram conductivity of a metal 110

Figure 3.16/3.14. Diagram depicting the effect of voltage on a slab of dielectric elastomer (adapted from Kornbluh et al). 112

Figure 4.1. Storage modulus of gels with different types of oil, a) 15 wt%, b) 25 wt%, c) 35 wt% SEBS concentration, P1 (diamond), P2 (square), P3 (circle(cirle)), P4 (triangle). 124

Figure 4.2. Loss modulus of the four gels with varying concentrations a) 15 wt% b) 25 wt % c) 35 wt %, P1 (diamond), P2 (square), P3 (circle), P4 (triangle). 125

Figure 4.3. Dynamic storage modulus, G' (close symbols) and loss modulus, G", (open symbols) presented as a function of oscillatory frequency (ω) at a strain amplitude of 1% at 25℃ for P4 gels with different amounts of oil with... 129

Figure 4.4. Dynamic storage modulus, G' (filled symbols) and loss modulus, G", (open symbols) presented as a function of oscillatory frequency (ω) at a strain amplitude of 1% strain for P4 gels with 15 wt% at temperature of 25℃... 130

Figure 4.5. The ω spectra of G' (filled symbols) and G" (open symbols) are displayed for gels with 15 wt% SEBS concentration with varying types of hydrocarbon oil, P1 (square), P2 (circle), P3 (triangle) and P4 (diamond). 130

Figure 4.6. Dynamic viscosities of the four gels with 35 wt % SEBS concentration P1 (diamond), P2 (square), P3 (circle), P4 (triangle). 132

Figure 4.7. Stress relaxation results displaying the G' (closed symbols) and G" (open symbols) moduli as a function of time for 25 wt% SEBS concentration with P3 hydrocarbon oil at different temperatures after a 0.3 % strain at... 133

Figure 4.8. Representative curves of relaxation time for P3 gels with 25 wt% concentration at 90℃ G' (closed symbol) and G" (open symbol). 133

Figure 4.9. Swelling ratio versus immersion time for three gels P1, P2 and P3 with 25% and 35% SEBS concentration. 135

Figure 4.10. Dependence of gelation temperatures of TPE gels on the different types and concentrations of hydrocarbon oils measured by dynamic rheometer (filled symbols) and tilting (open symbols)... 137

Figure 4.11. DSC curves for P3 gels of different triblock copolymerconcentrations 15%, 25% and 35%. 139

Figure 4.12. The glass transition temperatures (Tg) of styrene end-block of TPE gels with different types of hydrocarbon oil and concentrations, P1(diamond), P2 (square), P3 (circle). 139

Figure 4.13. Schematic representation of plasticized PS domains due to presence of aromatic in hydrocarbon oil. 140

Figure 4.14. SAXS scattering curves for: (a) neat SEBS (filled symbol) and open symbols for TPE gels with 25 wt% SEBS concentration of different types of oil P1 (square), P2 (circle) and P3 (triangle, (b) P4 TPE gels with 15 wt%... 144

Figure 4.15. SAXS frames for (a) neat SEBS and (b) P4 TPE gel with 15 wt% SEBS concentration. 145

Figure 4.16. Three typical TEM micrographs of ultrathin sections of an SEBS bulk sample. The PS domains appear dark caused by the RuO4 staining. 147

Figure 4.17. TEM of TPE gels. 148

Figure 4.18. Proposed mechanism of micelle network formed by SEBS with different types of hydrocarbon oil. 151

Figure 4.19. The gel strength properties of the four gels with varying concentrations in different types of oil a) gel strength b) elongation at break. 153

Figure 5.1. Dynamic storage modulus, G', presented as a function of temperature at a strain amplitude of 1% for parent TPE gels with oil/SEBS ratio of 4 (square) and for NCTPE gels with 5 wt% loading for different... 168

Figure 5.2. Dynamic storage modulus (G') (closed symbols) of NCTPE gels with different nanographite as a function of temperature:(a) EG1: 1 wt% (square), 3 wt% (up triangle), 5 wt% (circle); (b) EG2: 1wt% (square), 3wt%... 170

Figure 5.3. Dynamic storage modulus (G') (closed symbols) of NCTPE gels with CNTs: 0.5 wt% (hexagon), 1 wt% (right triangle), 3wt% (down triangle), 5wt% (star) and dynamic loss modulus (G") (open symbols) 5 wt % CNTs... 171

Figure 5.4. Dynamic storage modulus (G') (closed symbols) of NCTPE gels with CB pureblack 205: 2wt% (square), 5wt% (circle), 10wt% (up triangle), 15wt% (octagonal), 20wt% (diamond) and dynamic loss modulus (G") (open... 171

Figure 5.5. Storage modulus of (a) EG1 (square), EG2 (circle), xGnP15 (triangle) and xGnP1 (diamond); (b) MWCNTs (c) CB pureblack 205 as a function of nanoparticles concentrations, G' parent TPE gels with 20 wt%... 174

Figure 5.6. Maximum operating temperature of NCTPE gels modified (a) nanographites (b) MWCNT (c) carbon black (d) TPE gels. The data of TPE gels were taken from our study in Chapter 3 using P3 paraffin oil for... 177

Figure 5.7. Storage modulus, G', (closed symbols) and loss modulus, G", (open symbols) presented as a function of oscillatory frequency (ω) at a strain amplitude of 1% at 30℃ with different amounts of nanoparticles based... 180

Figure 5.8. Storage modulus, G', (closed symbols) and loss modulus, G", (open symbols) of CB pureblack 20℃ based TPE gels presented as a function of oscillatory frequency (ω) at 30℃. 181

Figure 5.9. Storage modulus, G', (closed symbols) and loss modulus, G", (open symbols) presented as a function of oscillatory frequency (ω) at a strain amplitude of 1% at 30℃ for 5 wt % of nanographite including MWCNTs. 181

Figure 5.10. Storage modulus, G', (closed symbols) and loss modulus, G", (open symbols) presented as a function of oscillatory frequency (ω)at 70 °C for 5% wt loading of (a) EG1 (b) EG2 (c) MWCNTs (d) CB pureblack 205 and... 183

Figure 5.11. TEM images of NCTPE gels modified with different nanographite (a), (a¹) EG 1 and (b), (b¹) xGnP1 and (c), (c¹) xGnP 15 Scale bar left : 2 ㎛ : right : 50 nm 186

Figure 5.12. SEM photos of EG1 based NCTPE gels (a) low magnification (a¹) highmagnification. TEM sample was used for SEM high magnification measurement. Scale bar (a) 100 ㎛ (a¹) 500 nm. 187

Figure 5.13. TEM images of 5 wt% MWCNTs based NCTPE gels (a) low magnification (a¹) high magnification. 187

Figure 5.14. TEM images of 20 wt% carbon black TPE gels (a) low magnification (a¹) high magnification. 188

Figure 5.15. Scheme illustration of NCTPE gels (a) EG1 (b) xGnP15 (c) MWCNTs 189

Figure 5.16. Atomic force microscopy images of NCTPE gels modified with (a) xGnP1 (b) xGnP15 (c) MWCNTs. 191

Figure 5.17. XRD patterns of NCTPE with different amounts of different nanographite (a) EG1 (b) EG2 (c) xGnP 1 (d) xGnP 15. 196

Figure 5.18. XRD patterns of NCTPE with different amounts of MWCNTs. 197

Figure 5.19. Glass transition curves for NCTPE gels (a) EG1 (b) EG2 and (c) MWCNTs. 198

Figure 5.20. TG-DTA of (a) neat SEBS (b) parent TPE gels. 202

Figure 5.21. (a) TG and (b) DTG of (1) parent TPE gel 5 wt % loading of (2) MWCNT, (3) xGnP 1, (4) xGnP15, (5) EG1 (6) EG2, (7) CB pureblack 205 based NCTPE gels. 203

Figure 5.22. Tensile strength of NCTPE gels with different nanographites such as EG1, EG2, xGnP1 and xGnP15, (a) MWCNTs (b) and carbon black Pureblack 205 (c). 209

Figure 5.23. Elongation at break of NCTPE gels with different nanographite (a)MWCNTs (b) and carbon black pureblack 205 (c). 210

Figure 6.1. Schematic representation of major categories of conduction models in composite materials (a) a uniform model (b) a uniform channel model (c) a non-tunneling barrier model (d) a tunneling barrier model 226

Figure 6.2. Dielectric constant of NCTPE gels modified with (a) EG 1 (b) EG2 (c) xGnP1 (d) xGnP15 (e) MWCNT and filled with (f) carbon black. 233

Figure 6.3. Comparison of dielectric constant data for NCTPE gels modified with (a) EG1; (b) CB 236

Figure 6.4. Variation of dielectric constant as a function of concentration with different frequencies (a) EG1 (b) EG2 (c) xGnP1 and (d) xGnP15. 238

Figure 6.5. Variation of dielectric constant as a function of concentration with different frequencies (a) MWCNTs (b) CB (pureblack 205). 239

Figure 6.6. Variation of dielectric constant as a function of frequency at different filler concentrations (a) EG1, (b) MWCNTs (c) TPE gels. 241

Figure 6.7. Typical dielectric properties of TPE gels as a function of temperature at different frequencies (a) ε' (b) ε". 243

Figure 6.8. Dielectric properties of NCTPE gels as a function of temperature at different frequencies xGnP1 (a) ε' (b) ε". An overlap of 1000 Hz and 10000 Hz. 243

Figure 6.9. Dielectric properties as a function of temperature at different frequencies for NCTPE gels with 1 wt % MWCNTs (a) ε' (a¹) ε" and 5 wt% MWCNTs (b) ε' (b¹) ε" 245

Figure 6.10. Loss tangent as a function of temperature in different frequencies (a) parent TPE gels (b) xGnP1 ; (c) MWCNTs-1 wt% (d) MWCNTs-5 wt% 247

Figure 6.11. Conductivity of NCTPE gels modified with nanographite (a) EG (b)EG2 (c) xGnP (d) MWCNTs and (e) filled with Pureblack 205 CB 250

Figure 6.12. Resistivity of NCTPE gels modified with nanographite (a) EG1 (b) EG2 (c) xGnP15 (d) MWCNTs (e) CB. 251

Figure 6.13. Effect of frequency on resistivity of NCTPE gels modified with different amounts and types of nanographite (a) EG1 (b) EG2 (c) xGnP1 and (d) xGnP15. 254

Figure 6.14. Effect of frequency on resistivity of NCTPE gels modified with different amounts of (a) EG1 (b) xGnP15 (c) MWCNTs and (d) carbon black 255

Figure 7.1. The polymer film is compressed and expands in area (as indicated by arrows) when voltage, V, is applied across the electrodes. 274

Figure 7.2. Hot-press used in the preparation of test sheets. 275

Figure 7.3. Grease electrodes 278

Figure 7.4. (a) sample with mask film (b) after brushing with electrode (c) final sample for actuator with different sizes. 279

Figure 7.5. TPE gels test specimens with copper wire electrode (a) shorter length with small distance between each other (b) copper wires are embedded(embeddeded) below and above the sample (c) spiral shape sandwiched between two sheets. 280

Figure 7.6. TPE film for actuator testing with different electrodes (a) carbon black (b) copper wire 281

Figure 7.7. Experimental actuation test set-up 282

Figure 7.8. Picture of TPE gels (a) off voltage (b) on voltage indicates the length changes that were imposed on the actuator by the muscle lever. Thickness is around 0.5 mm. 284

Figure 7.9. Pictures of NCTPE gels modified with 1wt% MWCNTs (a) off voltage (b) on voltage indicates the length changes that were imposed on the actuator by the muscle lever.... 286

Figure 7.10. Burned due to spark of electrode (a) TPE gels (b) nanocomposite TPE gels with xGnP15-3 (coated with electrode) 288

Figure 7.11/7.10. Failure of actuation due to (a) impurities (b) voids (c) damage due to copper wire (d) improper compliant electrode coating. 288