4(%3)3 - Ecole nationale supÃ©rieure de chimie de Montpellier

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Heating the multilayer micelle assembly in the solid dry state at 60°C for 1 hour, followed bycooling down to 25°C at 1°C min -1 led to an increase in the contact angle from 88±2° to 94±2° of thesurface. The AFM analysis (Figure – 4.23) of the surface thus obtained showed deformed particles inplace of the original micelle spheres.Figure – 4.23: Atomic Force Microscopy and water droplet images (inset) obtained for a) zipper assembly, b)deformed assembly due to melting of PODMA chains in dry state at 60 o C followed by recyrstallization.This deformation can be result increased amount of the crystalline part in between micellecores. To verify this, differential scanning calorimetry was conducted for block copolymer powder andmultilayer micelle assembly and t was calculated from the obtained scansusing the following equation: = ……….. Eq. (4.1)where f is the enthalpy of fusion of n-octadecyl methacrylate in the copolymer and f0 is theenthalpy of fusion of a crystal for alkyl side-chain polymers taken equal to f0 =219.8 J/g 33 . To maintainthe overall morphology of the multilayer assembly, the scans were stopped at 90 o C, before the glasstransition temperature of PMMA is reached. A clear decrease in crystallinity from 17.6 % to 13.5 % wasobserved (Table – 4.1) when comparing the 1st heating scans of the block copolymer powder and themultilayer micelle assembly. The spherical shape of micelles, like any curved surfaces is known to reducethe contact area required for the zipping and consequently decreasing the overall crystallization 23 also.As expected from the observed deformed particles, the 2nd heating scan of the micelle assemblyrevealed an increase of c to 17.1%, which stems due to the minimization of curved interfaces caused byheating and relative reorganization of PODMA pendant chains.120
Heating Cycle H f (J/g) c n cPMMA – b – PODMA powder 1 37.8 0.176 4.32 36.3 0.165 4.0PMMA – b – PODMA multilayer assembly 1 29.6 0.135 3.32 37.6 0.171 4.1Table – 4.1: Enthalpy of fusion and degree of crystallinity calculated from thermograms obtained for the copolymerpowder and assembled coating from the Differential Scanning CalorimetryThe number of side chain CH 2 groups (n c ) involved in crystallization process was calculated usingthe following equation:n c = .…….. Eq. (4.2)H is the average melting enthalpy per CH 2 unit for n-H CH2 = 3.07 kJmol -1 ) 34 .Using the above equation, the number of methylene groups involved was found to be around 4,representing 22% of the total methylene units, in agreement with the range 4.7 – 6.9 reported for purePODMA 34 .4.5 IMPLICATIONS FOR BEING A SELF-HEALING COATINGGiven the fact that it is possible to alter the organization of the micelle assembly withoutchanging the overall morphology by heating at 60 o C, we strongly believe that the discussed system hasthe potential to show self-healing ability in case of surface damage. Although not completelyautonomous due to application of temperature but a situation can envisioned where a minor surface cutor abrasion is erased or healed by heating the coated substrate at 50 o C – 60 o C. At this temperature, thependant long chains of PODMA shall reorganize themselves thus filling the space created by the damage.Furthermore, a porous superstructure can also be prepared by such block copolymer micelles by creatingpores into their assembly using methods such as breadth figure method.4.6 CONCLUSIONIn this chapter, we have explored the possibility of using macromolecular zipper to reversiblyassemble micelles into 2D and 3D coatings. The zipper effect was observed from the efficient networkedinterdigitation of pendant long chains of PODMA. First a 2D monolayer was zipped to a PMMA substratethrough a one pot strategy comprising of surface functionalization with anchoring points followed by a121
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THESISPRESENTED ATNATIONAL GRADUATE
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As the human civilization progress
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CHAPTER - 1 SELF-HEALING POLYMERIC
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8.1.5 Atomic Force Microscopy …
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Synthetic engineering materials in
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esponse to a specific external stim
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The first work based on this approa
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een prepared from urea-formaldehyde
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monomer systems. The addition of EN
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Figure - 1.10: Self-healing process
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was required to reach healing effic
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In addition to above works, some ot
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that have been identified to be tak
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part of the chapter, these material
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Figure - 1.17: Self-healing of the
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commercialized under tradenames; Nu
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joined together at temperature high
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Inspired by these findings, the fir
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temperature greater than 80 o C in
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Figure - 1.27: Sulfur chemistry bas
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A different kind of sulfur chemistr
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Figure - 1.29: Dynamic covalent che
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cracks. The recovered droplets afte
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23 White, S. R. et al. Autonomic he
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65 Taber, D. F. & Frankowski, K. J.
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107 Kushner, A. M., Vossler, J. D.,
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148 Park, J. S., Kim, H. S. & Hahn,
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The value of subscripts “n”,
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The formation of spherical micelles
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the micelle assembly showed the pre
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gain onto the electrodes by buildin
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The resistance R can be further exp
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empty-tower velocity U only depends
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This apparent morphological switchi
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In a further qualitative analysis,
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noteworthy and though its feasibili
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Furthermore within this range, lowe
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Figure - 2.22: Scanning Electron Mi
Page 80 and 81: While the resistance measurements g
Page 82 and 83: In conclusion, a self-healing membr
Page 84 and 85: 23 Giacomelli, F. C., Riegel, I. C.
Page 86 and 87: micelles enabled the membrane to se
Page 88 and 89: The second class is represented by
Page 90 and 91: To avoid the probable clogging of t
Page 92 and 93: 181614SP2 - iNumber of Particles121
Page 94 and 95: 1000900800y = 3E+06xR² = 0,9911y =
Page 96 and 97: very high value of 1.5 g.l -1 . Thi
Page 98 and 99: Since the only change in the membra
Page 100 and 101: 100Retention (%)8060400,100,20,40,6
Page 102 and 103: Figure - 3.18: Scanning Electron Mi
Page 104 and 105: (Figure - 3.20). A cursory look at
Page 106 and 107: When compared to poly(styrene) NPs,
Page 108 and 109: Figure - 3.24: Scanning Electron Mi
Page 110 and 111: REFERENCES1 Metzler, R. & Klafter,
Page 112 and 113: 46 Bemporad, D., Luttmann, C. & Ess
Page 114 and 115: In this chapter, preparation of 3D
Page 116 and 117: obtain complex macromolecular archi
Page 118 and 119: The polymerization was conducted at
Page 120 and 121: proceeds, lesser monomer is availab
Page 122 and 123: mg/ml),the micelles’ hydrodynamic
Page 124 and 125: Figure - 4.15: The monolayer and mu
Page 126 and 127: monolayer of micelles and topmost l
Page 128 and 129: The presence of the dispersed micel
Page 132 and 133: stable zipping of the micelles. Mul
Page 134 and 135: 24 Moad, G., Rizzardo, E. & Thang,
Page 136 and 137: The concept of nano-gel based self-
Page 138 and 139: Figure - 5.4: Size distribution of
Page 140 and 141: In a typical process, the two compo
Page 142 and 143: Figure - 5.10: 1HNMR spectra obtain
Page 144 and 145: The 1 HNMR spectrum obtained for th
Page 146 and 147: REFERENCES1 White, S. R. et al. Aut
Page 148 and 149: healing ability shown by the membra
Page 150 and 151: 7. PERSPECTIVESBeing the first such
Page 153 and 154: 8. MATERIALS & METHODSThis chapter
Page 155 and 156: 8.1.3 PEG Filtration MeasurementsTh
Page 157 and 158: addition of TEOS due to formation o
Page 159 and 160: solution was ultrasonicated for 15
Page 161 and 162: Triethylamine (TEA) (Sigma-Aldrich
Page 163 and 164: To prepare the monolayer assembly o
Page 165 and 166: was added followed by addition of 0
Page 168 and 169: ELABORATION OF SELF-HEALING POLYMER
Page 170 and 171: ELABORATION DES MEMBRANES POLYMERES
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4(%3)3 - Ecole nationale supÃ©rieure de chimie de Montpellier

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