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2.4.1.1.4 Various Mechanisms of Film Growth Understanding how the multilayers are structured and what governs their assembly is of great importance for tuning their physico-chemical properties. Two main modes of growth of polyelectrolyte multilayer films, namely linear and non-linear (supralinear or sublinear), have been recognized. The extent of deposited polyelectrolyte per adsorption step for consecutive steps distinguishes the two modes. Generally, strong polyelectrolytes with high charge densities and low ionic strength result in a linear growth. In this case, polyelectrolytes from the solution interact mostly with constituents of the film surface and less with more deeply buried molecules. In linear growth, combination of different techniques such as ellipsometry, SPM, X-ray and neutron reflectivity led researchers to establish a three zone model of the multilayer films(Decher, 1997; Ladam et al., 2000). The first zone consists of the first few polyelectrolyte layers being deposited close to the substrate surface. Typically, the amount of adsorbed polymer per deposition cycle increases during the initial 1 to 5 deposition cycles, and then approaches a constant value(Gero Decher, Lvov, & Schmitt, 1994; Lvov & Decher, 1994). It was observed that for poorly charged surfaces, this transition regime can even stretch over much more than 5 deposition cycles(Kotov et al., 1997; Lutt, Fitzsimmons, & DeQuan, 1998). The thickness per layer in this zone is smaller than in the second zone. The second zone is the bulk film, which contains interpenetrating layers of polyelectrolytes. Due to the proximity of the outer part of the multilayer, the local properties vary because of the solution environment and the increase in surface roughness(Decher, 1997). The third zone is comprised of one or a few polyelectrolyte layers close to the multilayer surface, including a diffuse double layer of counterions to maintain overall electroneutrality(Ladam, et al., 2000). On the contrary, the mechanism of exponential buildup processes is not clearly understood. The first suggestion for the phenomenon was an increase in film roughness with the number of deposited layers. Later experiments(Picart et al., 2002) suggested that non-linear (exponential) growth results from diffusion of polyelectrolyte molecules inward and outward from a film, while the film thickness is proportional to the amount of migrating polyion. The inward polyelectrolyte diffusion step causes supralinear growth and is favored by a non-homogeneous multilayer (Lavalle et al., 2002). Deposition of poly(L-lysine) (PLL) in the presence of a 78
polyanion such as hyaluronan (HA)(Picart, Ladam, et al., 2001) or poly(L-glutamic acid) (PGA)(Lavalle, et al., 2002) revealed that PLL chains diffuse in and out of the film during buildup. At the subsequent rinsing step, some of these free chains entrapped in the multilayer diffuse outward from the film but lots of chains still remain inside. In the next step, these remaining free chains were brought into contact with polyanions (HA or PGA) in solution. Due to electrostatic interactions between them, free PLL chains diffuse out of the film, resulting in the formation of PLL/polyanion complexes at the outer layer of the film. The amount of PLL chains that diffuse out of the multilayer in presence of the polyanion in solution determines the thickness of the new forming layer on top of the multilayer. The ability of the polyelectrolytes to diffuse inward and outward of the films (mostly seen for weak polyelectrolytes) can lead to an exponential growth system rather than a linear one. Film roughness is also increased with layer number due to charge mismatch between the polyanions and polycations, demonstrating more non-linear behavior(Bertrand, 2000). Hence, weak polyelectrolytes can display linear or exponential growth, but strong ones always show linear behavior. 2.4.1.1.5 Effect of Polyelectrolyte Concentration on Multilayers The available amount of polymer to be adsorbed is greater in solutions with higher polymer concentration than in solutions with lower polymer concentration, which leads to greater adsorption(Ferreira & Rubner, 1995). The main reason for greater adsorption in higher concentration solutions is the presence of more anchor sites, including loops and tails, on the substrate surface. This forces molecules to adopt a more compact orientation because of the severe competition of the polymeric chains. In lower polymer concentration solutions, there is less competition, and thus polymer chains straighten out, resulting in thinner layers and smaller adsorption. It was shown(Cheung, et al., 1997) that the bilayer thickness of polyaniline/PSS has an average value between 12 Å and 36 Å (Table 1), which increases by a factor of about three when the polyanion (PSS) solution concentration increases from 10 -4 to 10 -2 M. \ 79
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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
Page 73 and 74: measure the interfacial tension of
Page 75 and 76: a) b) Figure 2-6. Dependence of the
Page 77 and 78: Omonov et al. found double percolat
Page 79 and 80: 2.1.2.2.3 Effect of Composition on
Page 81 and 82: a) b) C B A c) Figure 2-12. SEM pho
Page 83 and 84: In the case where PS is the matrix,
Page 85 and 86: Posthuma de Boer, 1999) (Kumin & Ch
Page 87 and 88: lattice, such as square lattice, wi
Page 89 and 90: magnetization, which is a function
Page 91 and 92: Polymers have long been thought of
Page 93 and 94: epoxy as a function of nanotube wei
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: Figure 2-39. Macromolecule with a)
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 and 144: or model which predicts where the p
Page 145 and 146: concentration threshold for the ons
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
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Conductivity(S/cm) Ternary Blend 1,
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phase(PMMA), the concentration of P
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(6) Virgilio, N.; Desjardins, P.; L
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ONION MORPHOLOGY HDPE PVDF PS Contr
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work described above has focused on
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thermodynamic explanation to predic
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four-point probe increases continuo
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in the rheology tests were compress
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5.3.6 Layer-by-Layer Deposition The
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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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