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2.4.1.1.9 LbL Deposition on Curved Surfaces Numerous investigations for adsorption of polymer on rough and corrugated(Blunt, Barford, & Ball, 1989) or sinusoidal(Hone, Ji, & Pincus, 1987) substrate surfaces have been performed. The first investigations on macroscopically curved bodies was carried out by Alexander(Alexander, 1977). Of considerable interest is the adsorption of strongly charged polymers on oppositely charged spheres(Golestanian & Sens, 1999; Gurovitch & Sens, 1999; Wallin & Linse, 1996) and cylinders(Kunze & Netz, 2002; Odijk, 1980). It has been found that when the radius of the curved surface is much larger than the polymer size, this effect can be neglected. But when the polymer size is large enough, surface curvature has a great effect on polyelectrolyte adsorption on the substrate, whereas the electrostatic energy of the adsorbed polyelectrolyte layer depends strongly on curvature. Very small spherical substrates need a large amount of electrostatic energy to bend a charged polymer around them(Mateescu, Jeppesen, & Pincus, 1999; Nguyen & Shklovskii, 2001). Curvature disfavors adsorption of long, strongly charged polyelectrolytes at too low salt concentration, due to self-repulsion of the charged chains. 2.4.1.1.10 Effect of Roughness on the Multilayer Thickness The adsorbed polymer layer can be described in terms of loop and tail size distributions (Figure 2-37). It has been observed that the thickness of the adsorbed layer increases with an increase in the adsorption of loopy structures, leading to the deposition of correspondingly large amounts of polyelectrolyte. The relative weight of loops and tails in an adsorbed layer is a measure of entanglement of free polymers to this layer. Loops due to binding to the substrate at both ends are more prone to entanglements than tails. On the other hand, polymer loops dangling from the surface into the solution may entangle with free chains. Consequently, loop size distribution governs coupling between the bulk and the interface(Adjari et al., 1994). The monomers close to the wall mainly belong to loops, whereas the external part of the layer is mostly built up by the tails. This fold-forming of polymer chains (loops and tails) leads to an increase in film roughness. As the polymer concentration increases, the film surface roughness increases due to entangling more polymer chains to loops and tails. Surface roughness is also enhanced by 88
increasing the pH value due to a decrease in electrostatic repulsion and the prevention of molecular packing when the pH is raised(Braga, Paterno, Lima, Fonseca, & de Andrade, 2008). It can be concluded that the increase of loops and tails is proportional to the increase of surface roughness and adsorbed layer thickness. 2.4.1.1.11 Important Views on PANI/PSS LbL Adsorption General aspects: Rubner et al.(Cheung, et al., 1997) reported that adsorption of polyaniline onto a negatively charged surface occurs very rapidly. For the most concentrated solution, it took 5 min to reach complete adsorption, and in case of the least concentrated solution (around 10 -4 M) it took approximately 25 min. It was also mentioned that even for adsorption process as long as 24 hrs, no additional net adsorption was observed. Adsorption of bilayers of PANI/PSS has a linear rate and is independent of the number of layers deposited onto the substrate surface. Undoped and partially doped polyaniline can be dissolved in a wide variety of solvents, but doped polyaniline can be dissolved only in very strong solvents such as chromic acid. The poor nature of PANI-solvent interactions favors the spontaneous adsorption of polyaniline chains onto a variety of quite different substrates, including both hydrophilic and hydrophobic surfaces. It also demonstrates a significant aggregation of the polyaniline chains after 1-2 weeks. The film deposition process is very sensitive; films made by three different operators at the same conditions revealed three completely different thickness of PANI(Braga, et al., 2008). pH: The pH of the solution has a crucial influence on the stability of the solutions, doping and the adsorption process. A polyaniline solution is not stable for more than a couple of hours. No deposited layers have been observed by alternately dipping the substrate into a neutral polyaniline solution and a poly(styrene sulfonic) acid solution. The lower pH of a polyaniline solution has more positive charges because of the protonic acid doping, resulting in an increase of polyaniline adsorption by a factor of around 1.5. Consequently, a higher electrostatic repulsion is made between charges of polyelectrolytes such as PANI(Ferreira & Rubner, 1995). Polymer chains according to this electrostatic repulsion tend to straighten out and improve molecular packing. For this reason, a small number of PANI chains can approach the substrate surface and the amount of polymer adsorbed decreases. On the contrary, raising the pH results in a decrease 89
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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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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 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: As shown in Figure 2-44, swelling a
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
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
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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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