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usually utilized to explain the transition from discontinuous phase behavior to continuous phases. In conductive materials, this transition point is defined as the critical concentration of conductive phase required to build up a first conductive pathway and is referred to as the percolation threshold. The percolation threshold is generally defined as the onset of long-range connectivity in random systems. By employing a double percolated structure, the percolation threshold of the middle phase sharply decreases as its presence is limited only to the interface. The conductivity of a conductor-insulator blend near the percolation threshold point is calculated by the following equation: Equation 4-2. ( ) t σ σ p − p = 0 where σ is the conductivity at the percolation threshold point, σ is the conductivity of the 0 blend, p is the concentration of the conductive material, pc is the percolation threshold concentration, and t is a dimensionless index. The classic percolation threshold for a random dispersion of hard-core spheres in a matrix in three dimensions is approximately 16 volume percent(Scher & Zallen, 1970). Restricting the dispersed phase spatially, for example in interfacial tension driven structures such as a double- percolated morphology, can significantly reduce the percolation threshold of that phase. In that case the particles or polymer components can be precisely located at the interface leading to dramatic reductions in the percolation threshold value(Gubbels, et al., 1995; Gubbels et al., 1994; Zhang, et al., 2007). In other words, by controlling the morphology of the blend and restricting the pathways of the components, the percolation threshold deviates from the standard value of percolation threshold in a random system predicted by percolation theory. Moreover, using the same approach, controlling the morphology of the system can also influence the behavior of conductive systems. Confining the pathways of a conductive material in a multiphase system can result in high conductivities at low concentration of conductive material. The dimensionless index t in Equation 4-2 represents the effect of the morphology of the system on the conductivity behavior. This has already been shown to be possible for conductive systems where the conductive phase was selectively localized in the multiphase blend and consequently the c 98
concentration threshold for the onset of electrical conductivity was significantly decreased(Anand, et al., 1998). In the case of conductive fillers, both the size and shape of the particles influence the percolation threshold. Typically the percolation threshold ranges from 10-40% volume fraction of the conductive filler (Jagur-Grodzinski, 2002). It has also been theoretically and experimentally observed that for polymer blends including a dispersed metal(Bridge & Tee, 1990) or carbon black(Carmona, 1989) phase, that the percolation threshold depends on the aspect ratio of the filler and it decreases when the ratio of the length to the diameter increases(Munson-McGee, 1991). Gubbels et al. reported a percolation threshold as low as 3 weight percent carbon black when it is localized in one phase of a binary blend consisting of 45% polyethylene and 55% polystyrene(Gubbels, et al., 1995; Gubbels, et al., 1994). Then, they showed that localization of carbon black at the interface of a co-continuous PE/PS blend exhibits a sharp reduction in the percolation threshold value to 0.5 wt%. Blends consisting of conductive material prepared slightly above the percolation threshold have low conductivity. The most difficult part is preparing the conductive blend near the percolation threshold with reproducible conductive results. Sumita et al.(Sumita, Sakata, Asai, Miyasaka, & Nakagawa, 1991) employed the methodology of spreading coefficient to develop a criterion to determine the conditions of localization of carbon black at the interface. After the discovery of doped polyacetylene and its metal-like behavior, research shifted from carbon black to intrinsically conductive polymer blends (ICP). By replacing the inorganic semiconductors in conventional device structures with a semiconducting polymer, the basic application of these materials has already been demonstrated(Burroughes, Jones, & Friend, 1988). They can store information and energy, and are capable of performing intelligent functions. The most amenable conductive polymer to solution processing and meltprocessing(Paul, Vijayanathan, & Pillai, 1999) is polyaniline(PANI). Investigations by Macdiarmid et al.(Macdiarmid, et al., 1985), which resulted in the discovery of electrical conductivity for the emeraldine salt of polyaniline, led to an explosion of interest in this fascinating polymer. The emeraldine base of PANI is soluble in a few strong acids(Andreatta, Cao, Chiang, Heeger, & Smith, 1988). Various dopants were utilized to induce meltprocessability in PANI. The main disadvantage of all intrinsically conductive polymers including PANI is its limited melt-processability. The addition of zinc compound to doped-PANI complex 99
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© Sepehr Ravati, 2010. UNIVERSITÉ
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DEDICATED To my parents iii
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RÉSUMÉ Cette thèse présente, po
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devenir une structure hiérarchique
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ABSTRACT This thesis presents, for
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system can be increased from 10 -15
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CONDENSÉ EN FRANÇAIS Dans ce trav
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deuxième coquille de PS. Les phase
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structures à percolation multiple
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autre sous-type de morphologie dans
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TABLE OF CONTENTS DEDICATION.......
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xxiii 2.4.1.1.1 Charged Polymer Ads
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5.3.4 Annealing Test ..............
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xxvii REFERENCES ..................
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LIST OF FIGURES xxix Figure 1-1. a)
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Figure 2-12. SEM photomicrograph of
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Figure 2-34. Schematic view of diff
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Figure 4-8. SEM micrographs of vari
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Figure 5-6. a),b) Scanning electron
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and c) triangular concentration dia
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n number of moles p concentration o
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AFM atomic force microscopy LIST OF
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PS-co-PMMA copolymer of PS and PMMA
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1.1 Introduction CHAPTER 1 - INTROD
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Figure 1-2. Human heart, longitudin
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One of the applications for porous
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On the other hand, a novel tri-cont
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2.1 Polymer Blends CHAPTER 2 - LITE
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Based on Sterling’s approximation
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Antonoff’s rule (Equation 2-13) i
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2.1.2.1 Binary Polymer Blends 2.1.2
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Some other studies(Everaert, Aerts,
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where the parameter z is dependent
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“compatibilization” was suggest
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a) λ BC A and B are matrices, b) C
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Reignier & Favis, 2000, 2003a; Reig
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measure the interfacial tension of
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a) b) Figure 2-6. Dependence of the
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Omonov et al. found double percolat
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2.1.2.2.3 Effect of Composition on
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a) b) C B A c) Figure 2-12. SEM pho
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In the case where PS is the matrix,
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Posthuma de Boer, 1999) (Kumin & Ch
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lattice, such as square lattice, wi
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magnetization, which is a function
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Polymers have long been thought of
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Page 95 and 96: Figure 2-19. Approaching the percol
Page 97 and 98: Figure 2-21. Transmission electron
Page 99 and 100: Figure 2-22: Dependence of PE conti
Page 101 and 102: Figure 2-24. Plot of the total numb
Page 103 and 104: chain provides the conductive path
Page 105 and 106: 2.3.1.2.1 Polyaniline One of the mo
Page 107 and 108: CoPA/LLDPE/PANI blend and a poor-qu
Page 109 and 110: Narkis and co-workers extended and
Page 111 and 112: Figure 2-31: Conductivity of PVDF/P
Page 113 and 114: organic thin films, a novel and str
Page 115 and 116: on the topic have been reported in
Page 117 and 118: succeeded in creating thin films wi
Page 119 and 120: Addition of salt to the solution of
Page 121 and 122: different from that of linear homop
Page 123 and 124: Figure 2-39. Macromolecule with a)
Page 125 and 126: polyanion such as hyaluronan (HA)(P
Page 127 and 128: 2.4.1.1.7 Effect of Salt on Multila
Page 129 and 130: 2.4.1.1.8 Overcompensation of the M
Page 131 and 132: important factors determining the g
Page 133 and 134: As shown in Figure 2-44, swelling a
Page 135 and 136: increasing the pH value due to a de
Page 137 and 138: CHAPTER 3 - ORGANIZATION OF THE ART
Page 139 and 140: discussed above, HDPE, PS, PMMA, an
Page 141 and 142: CHAPTER 4 - LOW PERCOLATION THRESHO
Page 143: or model which predicts where the p
Page 147 and 148: chemical and weathering resistance,
Page 149 and 150: Table 4-1. Material Characteristics
Page 151 and 152: filled with blend pellets. To facil
Page 153 and 154: 4.3.6 Conductivity Measurements DC
Page 155 and 156: experimentally in this research gro
Page 157 and 158: a) b) c) d) Figure 4-4. Schematic i
Page 159 and 160: microstructure of the quaternary bl
Page 161 and 162: a) b) c) d) Figure 4-6. SEM microgr
Page 163 and 164: a) b) PVDF PS PMMA c) d) e) HDPE PS
Page 165 and 166: Uniform layers of PS and PMMA situa
Page 167 and 168: the concentration of HDPE is increa
Page 169 and 170: a) b) c) e) Figure 4-11. SEM microg
Page 171 and 172: melt-processable and contains 25 wt
Page 173 and 174: One question that should be address
Page 175 and 176: Conductivity(S/cm) Ternary Blend 1,
Page 177 and 178: phase(PMMA), the concentration of P
Page 179 and 180: (6) Virgilio, N.; Desjardins, P.; L
Page 181 and 182: ONION MORPHOLOGY HDPE PVDF PS Contr
Page 183 and 184: work described above has focused on
Page 185 and 186: thermodynamic explanation to predic
Page 187 and 188: four-point probe increases continuo
Page 189 and 190: in the rheology tests were compress
Page 191 and 192: 5.3.6 Layer-by-Layer Deposition The
Page 193 and 194: prepare a polymer blend structure w
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a) b) c) Figure 5-3. Scanning elect
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spontaneously self-assembled. After
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a) b) c) d) e) f) g) h) Figure 5-5.
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Since the ultra-low surface area va
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c) a) b) Figure 5-6. a),b) Scanning
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salt to a PSS polyelectrolyte solut
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A relationship between macropore si
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close together. It is interesting t
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Figure 5-9. Mass increase (%) indic
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In this work the conductance of the
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deposited PANI layers increases unt
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(52) Guo, H. F.; Packirisamy, S.; G
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6.2 Introduction It is well-known t
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modified version of Harkins theory(
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6.3 Experimental 6.3.1 Materials Co
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Complex voscosity (Pa.s) 1,0E+04 1,
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6.3.5.2 Focused Ion Beam (FIB) and
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a) c) b) d) e) f) PMMA PMMA HDPE HD
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y Harkins theory, PS will always si
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a) b) c) d) e) f) PS Figure 6-6. a)
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a) b) HDPE : black PS : grey PMMA :
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6.4.6 Continuity, Co-continuity, an
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c) V III II I VII I IV VI Figure 6-
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Continuity Scheme (a) Figure 6-10.
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Addition of a low concentration of
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Addition of small amounts of HDPE t
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icontinuous network with the HDPE.
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Three examples are shown in Figure
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(9) Mekhilef, N.; Verhoogt, H. Poly
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structures are formed due to the co
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CONCLUSION AND RECOMMENDATIONS In t
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REFERENCES A. K. Gupta, K. R. S. (1
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Caruso, F. (2003). Hollow Inorganic
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Domenech, S. C., Bortoluzzi, J. H.,
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Geuskens, G., Gielens, J. L., Geshe
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Hou, S., Harrell, C. C., Trofin, L.
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Krass, H., Papastavrou, G., & Kurth
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Macdiarmid, A. G., Jin-Chih, C., Ha
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Niziol, J., & Laska, J. (1999). Con
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Reghu, M., Yoon, C. O., Yang, C. Y.
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Shirakawa, H., Louis, E. L., MacDia
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Utracki, L. A. (1991). On the visco
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Yasuda, K., Armstrong, R., & Cohen,
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literature has examined factors inf
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(Reignier & Favis, 2000, 2003a; Rei
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Table A-1.2. Interfacial tensions a
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acquisition of images with a very h
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Table A-1.3. Continuity of the PMMA
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(17) Reignier, J.; Favis, B. D., Ma
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PANI. Theoretically, the extent of
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Equation A-2.7 0( ) 0 1. 5 σ = σ
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Cumulative Mass × 10 5 (g) dipping
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of PANI, and an increase in the con
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Resistance(ohm) 1.0E+12 1.0E+11 1.0
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esistance value. Samples containing
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The results of resistance for PS/PE
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Caruso, F., & Schuler, C. (2000). E
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