Title Page

Contents

ABSTRACT 14

SUMMARY 17

Chapter 1. Introduction 19

1.1. Scope of this study 20

1.1.1. Composite material and its applications 24

1.1.2. Advent of multifunctional electronics 25

1.1.3. Challenges in materials and architecture 27

1.2. Background 30

1.2.1. Layered composite structure 30

1.2.2. Conducting polymers 31

1.2.3. Core-shell particles (CSPs) 39

1.2.4. Graphene 47

1.2.5. Deposition techniques 54

1.2.6. Basic mechanism of electromagnetic interference (EMI) shielding 63

References 67

Chapter 2. Synchronous Polymerization of Poly(3,4-ethylenedioxythiophene) and Polypyrrole by PECVD Technique: Thin film hybrid-coating for bandgap adjustment 80

2.1. Introduction 82

2.2. Experimental 84

2.2.1. Materials 84

2.2.2. Synchronous fabrication of PEDOT/PPy thin film hybrid-coating by PECVD technique 84

2.2.3. Characterization 86

2.3. Results and discussion 87

2.3.1. Deposition rate of PEDOT/PPy thin film hybrid-coating 87

2.3.2. SEM and AFM results of PEDOT/PPy thin film hybrid-coating 88

2.3.3. FT-IR and XPS results of PEDOT/PPy thin film hybrid-coating 90

2.3.4. Electrical properties of PEDOT/PPy thin film hybrid-coating 94

2.3.5. Bandgap of PEDOT/PPy thin film hybrid-coating 95

2.4. Conclusions 98

References 99

Chapter 3. pH-responsive Aggregation-mediated Assembly of Reduced Graphene Oxide on Polymer Microspheres: RGO curved type layered structure for tunable electrical properties 105

3.1. Introduction 107

3.2. Experimental 109

3.2.1. Materials 109

3.2.2. Fabrication of amine modified poly (glycidyl methacrylate) (PGMA) microspheres 109

3.2.3. Fabrication graphene oxide (GO) suspension 110

3.2.4. Fabrication of RGO/PGMA-ed core-shell structure by electrostatic-self-assembly method 111

3.2.5. Characterization 112

3.3. Results and discussion 113

3.3.1. FT-IR spectra, SEM and zeta potential results of pristine PGMA-ed 113

3.3.2. Raman spectroscopy, SEM, TEM and zeta potential results of pristine GO 114

3.3.3. Surface morphology and cross-sectional image of RGO/PGMA-ed core-shell observed by SEM and TEM 118

3.3.4. Electrical property of RGO/PGMA-ed core-shell microsphere 122

3.4. Conclusions 125

References 126

Chapter 4. EMI Transparent Shielding of Reduced Graphene Oxide Interleaved Structure Fabricated by Electrophoretic Deposition: RGO/polymer multilayered structure 129

4.1. Introduction 131

4.2. Experimental 133

4.2.1. Materials 133

4.2.2. Preparation of RGO suspension and PEI emulsion 134

4.2.3. Fabrication of PEI/RGO film by alternating EPD process 135

4.2.4. Characterization 138

4.3. Results and discussion 139

4.3.1. Detachment of single-PEI/RGO and fabrication of double-PEI/RGO by compression molding 139

4.3.2. RGO/PEI morphology observed by FE-SEM and TEM and Raman spectra results of RGO 142

4.3.3. Optoelectronic properties of RGO/PEI films 146

4.3.4. Mechanism of EMI SE measurement and EMI shielding efficiency (SE) results 148

4.4. Conclusions 154

References 155

Chapter 5. Conclusions 161

논문요약 165

Table 2.1. Assignment of different peaks observed in FT-IR analysis. FT-IR transmissions... 92

Table 2.2. Atomic composition of the plasma polymerized pristine PEDOT, PPy and... 94

Table 3.1. Electrical properties for the RGO/PGMA-ed core-shell microspheres 124

Table 4.1. Electrical conductivity and light transmittance of pristine PEI, single-PEI/RGO... 147

Figure 1.1. Schematic illustration of categorized research topics with different types of... 23

Figure 1.2. Global composite market growth (2014 – 2020) by application area. 25

Figure 1.3. Multi-functionalization of electronic devices through technology... 26

Figure 1.4. The growth of flexible electronic market predicted by IDTechEx. 27

Figure 1.5. Key challenges for future electronic market: Integration of an appropriate... 28

Figure 1.6. Schematic illustration showing advantages of each layered structure with... 30

Figure 1.7. Log-scale conductivity chart demonstrating approximate conductivities of... 33

Figure 1.8. Optoelectronic properties of several representative conducting polymers. 37

Figure 1.9. Core-shell polymers (CSPs) consisting of central part, which may be a solid,... 40

Figure 1.10. Schematic of suspension polymerization. 41

Figure 1.11. Schematic representation of emulsion polymerization. 43

Figure 1.12. Schematic models for the particle nucleation and growth of sterically-... 45

Figure 1.13. Schematic representation of seeded polymerization allowed by swollen... 46

Figure 1.14. Molecular models show the conversion process from graphite to chemically... 49

Figure 1.15. Schematic representation of self-standing RGO membrane without using... 51

Figure 1.16. Schematic of plasma enhanced chemical vapor deposition (PECVD). 55

Figure 1.17. Schematic illustration of electrostatic force (attraction and repulsion) acting... 58

Figure 1.18. Schematic representation of EPD process. 60

Figure 1.19. The distribution of planes and potentials at the surface of negatively charged... 62

Figure 1.20. Schematic representation of EMI shielding mechanism. 64

Figure 2.1. Schematic representation of experimental setup for plasma polymerization of... 86

Figure 2.2. Deposition rate of the plasma polymerized PEDOT/PPy copolymer films as... 88

Figure 2.3. Cross section and surface roughness of the PEDOT/PPy copolymer films... 89

Figure 2.4. FT-IR result of pristine EDOT, pyrrole monomers, and PEDOT/PPy... 91

Figure 2.5. Deconvolution of XPS spectra of C 1s (A), O1s (B), S 2p (C) and N 1s (D)... 93

Figure 2.6. Plot of hν vs. reaction powers for iodine-doped PEDOT/PPy copolymer... 95

Figure 2.7. UV-vis. absorbance spectra of (A) PEDOT/PPy copolymer films with a film... 97

Figure 3.1. Schematic representation of free radical polymerization of PGMA by... 110

Figure 3.2. FT-IR spectra of PGMA and PGMA-ed (a), SEM image (b) and zeta-... 114

Figure 3.3. SEM (a) and TEM (b) images of GO, Raman spectra of GO and graphite (c),... 115

Figure 3.4. XPS spectra of GO/PGMA-ed (a) and RGO/PGMA-ed (b). 117

Figure 3.5. SEM images of RGO/PGMA-ed core-shell microspheres prepared at pH 10... 119

Figure 3.6. TEM results showing cross-sectional images of RGO/PGMA-ed core-shell... 121

Figure 3.7. Electrical resistance (a) and conductivity (b) for the RGO/PGMA-ed core-... 123

Figure 4.1. Schematic of alternating anodic and cathodic EPD process, where the... 137

Figure 4.2. Schematic of PEI/RGO bilayer film fabrication. SS plate (A), RGO layer... 140

Figure 4.3. Schematic of double-PEI/RGO film fabrication. [PEI/RGO/PEI/RGO/PEI] 141

Figure 4.4. SEM images of RGO surface (A), q-PEI surface coated on RGO (B), TEM... 145

Figure 4.5. Light transmittance of two layers of pristine PEI (green line), single-PEI/RGO 147

Figure 4.6. Schematic of two waveguide-to-coaxial adapters and a vector analyzer used... 149

Figure 4.7. Description of wave dispersion on RGO film (A), the percentage of average... 153