BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:Molecular insight in fracture of soft materials DTSTART:20190325T131500 DTEND:20190325T141500 DTSTAMP:20260427T230508Z UID:be9ceeccbbc1d5887ceb43b2580f8c53e09f43ba5979af4aa24ac617 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Costantin Creton\, Soft Matter Science and Engineering L aboratory\, ESPCI ParisTech\nFracture of soft materials is a complex proce ss coupling non linear mechanics and statistical physics[1]. Because of th e large deformations involved before a crack propagates\, molecular damage typically occurs in the bulk of the material and not only in the fracture plane[2]. This is particularly true for tough soft materials where bulk e nergy dissipation mechanisms such as sacrificial bonds are introduced by d esign. Until recently the detection of damage ahead of a crack was limited to the detection of crystallization or cavitation\, detectable by wide or small angle X-ray scattering or optical visualisation\, but molecular bon d scission was not directly detectable. However organic chemists have now developed several molecules that respond to applied forces or bond scissio n by changing their light absorption or emission properties[3] providing n ovel opportunities for materials scientists to gain insight in molecular p rocesses occurring during mechanical loading.\nWe have incorporated mechan osensitive molecules as crosslinkers in model transparent soft polymer net works containing sacrificial bonds and used them to detect and map stresse s and molecular damages before and during crack propagation. Spyropyran ca n be used to detect stresses in real time and to distinguish loaded region s from unloaded ones. Dioxetane based molecules emit light when they break and can be used to obtain time resolved information on the bond scission process and pi-extended anthracene can be used to obtain high resolution s patial information. A combination of several techniques is needed to inves tigate the temporal and spatial process of damage in soft and tough materi als in order to develop proper molecular models and guide the design of no vel materials. We will focus on the mechanisms occurring during crack prop agation and necking of multiple network elastomers where a stiff and highl y stretched network is embedded in a more extensible matrix{Millereau\, 20 18 #5305} .\nReferences\n[1]        C. Creton\, M. Ciccotti\, Rep P rog Phys 2016\, 79\, 046601\; C. Creton\, Macromolecules 2017\, 50\, 8297. \n[2]        E. Ducrot\, Y. Chen\, M. Bulters\, R. P. Sijbesma\, C. Creton\, Science 2014\, 344\, 186.\n[3]        R. Gostl\, R. P. Si jbesma\, Chemical Science 2016\, 7\, 370\; Y. Chen\, A. J. H. Spiering\, K arthikeyanS\, G. W. M. Peters\, E. W. Meijer\, R. P. Sijbesma\, Nature Che mistry 2012\, 4\, 559\; D. A. Davis\, A. Hamilton\, J. Yang\, L. D. Cremar \, D. Van Gough\, S. L. Potisek\, M. T. Ong\, P. V. Braun\, T. J. Martinez \, S. R. White\, J. S. Moore\, N. R. Sottos\, Nature 2009\, 459\, 68.\n\nB io: 1985 : BS\, Materials Science & Engineering\, EPFL \, Switzerland\n199 1 : Ph. D. Cornell University\, USA\n1992-1993 : Research Fellow\, IBM Alm aden\, USA\n1994-2001:  CNRS Researcher (Assistant Professor) at the ESPC I\, Laboratory of Physical Chemistry of Polymers\, Paris\, France\n2001-  :  CNRS Research Director (Professor) at the ESPCI\, Laboratory of Physi cal Chemistry of Polymers\, Paris\, France\n  LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201 STATUS:CONFIRMED END:VEVENT END:VCALENDAR