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water showed little or no healing. Encapsulation via Urea-formaldehyde encapsulation and reversephaseencapsulation techniques remained problematic for aforementioned five solvents. The onlysolvent which could be encapsulated with relatively ease wasFigure – 1.12: Solvent based healing system, a) Influence of different solvents on healed peak fracture load, b) Load– displacement curve obtained for short – groove samples 78 .chlorobenzene, encapsulated into microcapsules having average diameter of 160 µm. However themaximum healing efficiency obtained was 82% with 20 wt% capsules loading (Figure – 1.12b).Correspondingly, xylene gave a 38% healing efficiency while that for hexane gave 0%, indicating adependence of healing efficiency on the solvent polarity. In a continuation of the above work, furtherenhancements were reported for solvent-based self-healing of epoxy materials 79 . First, in place ofmicrocapsules filled with solvent, a mixture of epoxy resin and solvent was used. This modificationyielded a complete recovery of fracture toughness after crack propagation. Multiple healing events werealso reported for this system. Second, less toxic solvents including aromatic esters giving efficient healingreplaced more toxic chlorobenzene. A stable shelf-life of one month was also reported for epoxy-solventsystem under ambient conditions for both chlorobenzene and phenyacetate. Similar encapsulationapproach has been used in case of thermoplastic PMMA thin films where a plasticizer (Dibutylphthalate)was encapsulated in urea-formaldehyde microcapsules and dispersed into PMMA thin films 80 . Upon,rupture, the DBP is released into the crack where it plasticizes and swells surrounding polymer leading tothe mending of the crack. The use of DBP helps in maintaining the optical properties of the preparedfilms and healed films also. Although no mechanical properties data was presented, the authors claimedto have recovered most of the protective properties of the virgin film along with certain portion ofmechanical properties.15
In addition to above works, some other novel reactive systems have also been investigated inconjugation with encapsulation technique. One of these systems is isocyanate encapsulatedmicrocapsules 40 , which is capable of performing healing in wet or humid conditions. This eliminates theneed to use of a catalyst in the composite material. The isocyanate employed was isophoronediisocyanate encapsulated in polyurethane microcapsules prepared via interfacial polymerization ofpolyurethane prepolymer in an oil-in-water emulsion. The mean diameter of microcapsules and agitationrate followed an inverse power law relationship and isocyanate loss for a half year period was less than10 wt%. In a more recent similar work 81 , microcapsules containing a reactive amine with potentialapplications in self-healing polymers were prepared by interfacial polymerization of an isocyanate and anamine stabilized by an inverse pickering emulsion. The microcapsules were successfully isolated, dried,and redispersed in epoxy. Upon rupture, the capsules released the core material thereby able to cure theepoxy to form a polymer film. Click-chemistry has also been presented as a potential chemistry forhealing materials. In one such work 31 , a liquid azido-telechelic three-arm star poly(isobutylene) polymerand trivalent alkynes were encapsulated into micron-sized capsules and embedded into a high molecularweight poly(isobutylene) matrix. Using (Cu(I)Br(PPh 3 ) 3 ) as low temperature catalyst for the azide/alkyne-"click"-reaction, crosslinking of the two components at 40 o C was observed within 380 min and as fast as10 min at 80 o C. Significant recovery of the tensile storage modulus was observed in a material containing10 wt% capsules. Though promising, the approach still relies on the incorporation of a catalyst which isair sensitive, thus losing its activity over the surface of the material. Living polymerization techniques likeATRP 82 and RAFT 83,84 have also been explored where liquid monomer (glycidyl methacrylate) isencapsulated in microcapsules. Again, these systems though attractive, still posses inherent limitations.In case of ATRP, being air-sensitiveness of the catalysts used, the surface healing cannot occur as theyget deactivated being in contact with humidity. Also, the metal ions are reported to accelerate thedegradation of the material. Additionally, since the polymerization needs heating well above roomtemperature, hence it cannot be called an autonomous healing system. The RAFT approach althoughskips the problem of deactivation but still requires heating of the matrix for effective healing hencecannot be termed under autonomous healing systems. In place of microcapsules, use of carbonnanotubes as reservoirs has also been proposed via simulation studies 85,86 which will not only givehealing ability but also boost mechanical and electrical properties for advanced applications.1.3.2 Microvascular NetworksThe microvascular approach is another novel approach which draws maximum inspiration fromnature to create most biomimetic synthetic material. Although this methodology shares basics with the16
Page 1: THESISPRESENTED ATNATIONAL GRADUATE
Page 4 and 5: As the human civilization progress
Page 6 and 7: CHAPTER - 1 SELF-HEALING POLYMERIC
Page 8: 8.1.5 Atomic Force Microscopy …
Page 11 and 12: Synthetic engineering materials in
Page 13 and 14: esponse to a specific external stim
Page 15 and 16: The first work based on this approa
Page 17 and 18: een prepared from urea-formaldehyde
Page 19 and 20: monomer systems. The addition of EN
Page 21 and 22: Figure - 1.10: Self-healing process
Page 23: was required to reach healing effic
Page 27 and 28: that have been identified to be tak
Page 29 and 30: part of the chapter, these material
Page 31 and 32: Figure - 1.17: Self-healing of the
Page 33 and 34: commercialized under tradenames; Nu
Page 35 and 36: joined together at temperature high
Page 37 and 38: Inspired by these findings, the fir
Page 39 and 40: temperature greater than 80 o C in
Page 41 and 42: Figure - 1.27: Sulfur chemistry bas
Page 43 and 44: A different kind of sulfur chemistr
Page 45 and 46: Figure - 1.29: Dynamic covalent che
Page 47 and 48: cracks. The recovered droplets afte
Page 49 and 50: 23 White, S. R. et al. Autonomic he
Page 51 and 52: 65 Taber, D. F. & Frankowski, K. J.
Page 53 and 54: 107 Kushner, A. M., Vossler, J. D.,
Page 55: 148 Park, J. S., Kim, H. S. & Hahn,
Page 58 and 59: The value of subscripts “n”,
Page 60 and 61: The formation of spherical micelles
Page 62 and 63: the micelle assembly showed the pre
Page 64 and 65: gain onto the electrodes by buildin
Page 66 and 67: The resistance R can be further exp
Page 68 and 69: empty-tower velocity U only depends
Page 70 and 71: This apparent morphological switchi
Page 72 and 73: 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
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While the resistance measurements g
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In conclusion, a self-healing membr
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23 Giacomelli, F. C., Riegel, I. C.
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micelles enabled the membrane to se
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The second class is represented by
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To avoid the probable clogging of t
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181614SP2 - iNumber of Particles121
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1000900800y = 3E+06xR² = 0,9911y =
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very high value of 1.5 g.l -1 . Thi
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Since the only change in the membra
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100Retention (%)8060400,100,20,40,6
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Page 104 and 105:
(Figure - 3.20). A cursory look at
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When compared to poly(styrene) NPs,
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Page 110 and 111:
REFERENCES1 Metzler, R. & Klafter,
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46 Bemporad, D., Luttmann, C. & Ess
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In this chapter, preparation of 3D
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obtain complex macromolecular archi
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The polymerization was conducted at
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proceeds, lesser monomer is availab
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mg/ml),the micelles’ hydrodynamic
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Figure - 4.15: The monolayer and mu
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monolayer of micelles and topmost l
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The presence of the dispersed micel
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Heating the multilayer micelle asse
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stable zipping of the micelles. Mul
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24 Moad, G., Rizzardo, E. & Thang,
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The concept of nano-gel based self-
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Figure - 5.4: Size distribution of
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In a typical process, the two compo
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Figure - 5.10: 1HNMR spectra obtain
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The 1 HNMR spectrum obtained for th
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REFERENCES1 White, S. R. et al. Aut
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healing ability shown by the membra
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7. PERSPECTIVESBeing the first such
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8. MATERIALS & METHODSThis chapter
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8.1.3 PEG Filtration MeasurementsTh
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addition of TEOS due to formation o
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solution was ultrasonicated for 15
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Triethylamine (TEA) (Sigma-Aldrich
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To prepare the monolayer assembly o
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was added followed by addition of 0
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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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