Self-healing and thermoreversible rubber from supramolecular assembly

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1 Self-healing and thermoreversible rubber from supramolecular assembly Philippe Cordier, François Tournilhac, Corinne Soulie-Ziakovic i & Ludwik Leibler "For outstanding theoretical contributions to the fundamental understanding of self-assembly of diblock copolymers and gels, and wetting." NATURE Vol February 2008

2 Ludwick Leibler PhD : 1976 in Theoretical Physics from Warsaw Universiy two years post-doc College de France in Paris and Saclay, France. In 1989: Médaille d Argent (Silver Medal) from CNRS. From 1996 to 2003 he was the founding director of a joint laboratory betwceen NRS and chemical company Elf Atochem (later AROFINA) which regrouped researchers from academia and industry. In 2001 he became an Adjunct Professor of Soft Matter and Chemistry at Ecole Superieure de Physique et Chimie Industrielles in Paris In 2006 he was awarded Polymer Physics Prize by the American Physical Society In 2007 he received Polymer Chemistry Award by the American Chemical Society. He is currently Director of Research at the CNRS and adjunct Professor of Soft Matter and Chemistr at Ecole de Physique et Chimie Industrielles in Paris. His current projects deal with macromolecular and supramolecular systems and in particular with blends, copolymers, and networks He is an associate editor of Macromolecules.

3 What defines a supramolecular polymer?

4 What defines a supramolecular polymer? Made out of repeating units held together by other bonds than just covalent bonds Strong Unidirectional association Uncontrolled multidirectional association Three main categories of supramoleular l polymers: coordination π stackingg hydrogen bonding Polymer chemistry comes full circle

5 Supramolecular polymers based on hydrogen bonding Hydrogen bonds hold a prominent place in supramolecular chemistry due to their directionality and versatility Multiple hydrogen bonds with a high association constant are required to obtain significant ifi degree of polymerisation so Multiple hydrogen bonds in a functionnal unit is a valuable tool to increase the strenght of this interaction

6 Major commercial source of natural rubber Rubber trees Hevea brasiliensis (Euphorbiaceae) -Synthetic rubberbroad study covered by polymer science And rubber technology milky emulsion Latex being collected from a tapped rubber tree

7 Rubber s properties: - Low Shear Modulus µ (about ) - Extensibility, Weakness - Self repairing properties for thermoreversible rubbers What is elasticity? Elasticity : property of complete and immediate recovery from an imposed displacement on release of the load, Elastic limit : the value of stress at which the material experiences a permanent residual strain that is not lost on unloading

8 Supramolecular polymers s concept -Ditopic molecules- Able to associate directionally with two other molecules Supramolecular Network Ditopic and multitopic molecules

9 What they did to avoid crystallisation while keeping strong directionnal interaction??? Mixtures of molecules l bearing a variety of strongly associating groups Variety of molecular architectures to render crystallisation difficult Entropy of mixing Directionnal specific interactions

10 Synthesis pathway + Fatty acids 1) 2) A Translucent glassy plastic T = 90 C > T g = 28 C : Soft rubber T > 160 C > T g = 28 C:Viscoelastic liquid Soluble in benzyl alcohol and CH 3 OH/CH 3 Cl mixtures

11 First step: side reactions Diethylenetriamine Diethylenetriamine Acylation at 160 C Ammonium salt meltsaround 120 C Imidazolines at more elevated T

12 Second step: condensation of urea with oligoamidoamines

13 Resonnance magnetic resonnance signals A is made of small molecules : oligomers

14 Normalized ATR infraredspectra cm 1 for different T 25 C, 50 C, 80 C, 110 C, 140 C, 170 C C=O stretching signals of: Imidazolidone (1697 cm 1 ) Amide (1649 cm 11 ) Urea (1604 cm 1 ) N H bending Isobestic point 1530 cm 1 dissociation of multiple H bonds between N H and C=O species when increasing the T

15 X-ray scattering spectra of compounds A ( ) and B ( ) A + dodecane B ξ 80 Å ξ 130 Å Tg: 8 C Non-tacky rubber-like material 0.17 for B 0.19 for A Mesoscopic organisation 1.4 A : absence of crystallisation Swelling by dodecane improves short range organization

16 Frequency dependence of the storage (top,g ) and loss (bottom, G ) moduli of compound B obtained by classical time temperature superposition shifts Reference T = 50 C 50 C : green circles 70 C : purple diamond 90 C : black triangles At plateau, the storage modulus is about Pa, and the relaxation time extrapolated from these data are not less than 3 millions seconds (few weeks)

17 Stress-strain curves Graphical measure of a material s mechanical properties derived from measuring the load applied on the sample, and strain, derived from measuring the deformation of the sample steel Cemented tungstene carbide E = ε σ E : elastic strain ε: young s modulus of elasticity σ: stress Plaster of Paris Soft rubber

18 Can torn or ripped rubber be repared by simply being placed back in contact at room temperature??? Magic healing according to Leibler s team at the «Matière molle et chimie laboratory» yes it can «The potential applications are manifold» Justin Mynar and Takuzo Aida of the school of engineering at the university of tokyo, «tears in clothes that effectively stitch themselves together, long lasting coatings and paints for houses and cars, and to take one example on the medical front, self repairing artificial bones and cartilage» This research was carried out in close collaboration with the chemical company Arkema, which is currently developing products and materials with industrial potential based on these results

19 Stress strain curve of supramolecular rubber B Strain at break After elongation to 300% with a speed of 2.5 mm.min -1 and release of stress, the residual strain is less than 5% When the cycle is repeated the sample recovers completely l without ih any residual strain

20 Creep recovery experiment of compound B performed at 50 C 144% applied stress: 5,000 Pa (green) 0.36% / hour 20,000 Pa (purple) s 0.04% / hour 32 % Applied stress is less than 8 % The sample completely ltl recovers its dimensions

21 Self-mending at room temperature B made of oligomers behaves very much like a rubber. exhibits unique self-healing properties Different contact times The cycle of streching, breaking and healing can be repeated many times

22 Stress strain behaviour at 40 C of mended samples Mending was performed at 20 C after mending was performed at 20 C after keeping broken samples apart for 6 h keeping broken samples apart for 18 h

23 Tensile stress relaxation experiments of compound B for two elongation rates at 40 C elongation rates: 0.5 mm/mn (1) 10 mm/mn (2)

24 Maximum waiting time after which healing is no longer possible one week at 23 C 48 h for waiting time at 40 C 95 min at 60 C 15 min at 90 C 5 min at 120 C equilibrium is reached much more quickly when temperature is raised, and so broken associating groups find partners within the broken piece much faster A freshly cut surface does not adhere to the surface of a non-broken sample at room T

25 Infrared absorption spectra evolutions free N H bending motions associated N H bending motions Long lifetime of open hydrogen bonds when they are created in excess Time-dependent infrared experiments The sample was heated to 125 C for 10 min and then quenched to 25 C.

26 Conclusion Nowadays the field of supramolecular plymers is generating severa technological applications Hydrogen bonded systems have shown to become of technological relevance and surpass the state to being scientific curiosities only. «New form of elastic has developed with life like properties» I think it will have a lot of uses, it is just a matter to use your imagination If i happen to wear clothes make of this wonder material and sit down on a chair made with smilar self-healing fabric, will i find myself promoted to chairwomen????

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