Equipe d`accueil / Hosting Team : Equipe Soft Polymer Networks
Transcription
Equipe d`accueil / Hosting Team : Equipe Soft Polymer Networks
Equipe d'accueil / Hosting Team : Equipe Soft Polymer Networks Site Web / Web site :http : https://www.ppmd.espci.fr/spip.php?rubrique10 Responsables du stage (encadrants) / Direct Supervisor : Costantino Creton, Pierre Millereau Tél / Tel : 01 40 79 46 83 E-mail : [email protected], [email protected] Période de stage / Internship period: janvier-juillet 2016 Gratification / Salary : ~546 Euros/mois Possibilité de continuer en thèse : Oui Background Nominal stress (MPa) Simple networks of elastomers have very poor mechanical properties. They are generally either stiff and brittle, or soft and extensible depending on the amount of crosslinker. In partnership with DSM research, we recently succeeded in combining the two kinds of networks into a bicontinuous interpenetrated structure which is able to increase both stiffness and extensibility1 and results in extremely tough unfilled elastomers: perfectly elastic at low and moderate strains but highly dissipative at large strains, delaying crack propagation. The synthesis developed in the lab is carried out with UV light and in multiple steps of free radical polymerization to obtain these bicontinuous and interpenetrated networks. SN = 1step, DN = two steps, TN = 3 steps and QN = 4steps. 10 Such unique combination of properties for an unfilled QN elastomer is due to the existence, inside the material, of TN 8 polymer chains with a multimodal level of prestretching. 6 4 Subject of the internship QN DN The objective of this internship is to synthesize and characterize new types of multiple networks with finely tuned prestretching levels. Only a few systems have been SN 0 made for the moment and many questions remain. In 1.0 1.5 2.0 2.5 3.0 Lambda particular the influence of the transfer reactions occurring during the different synthesis remains to be studied, and a solution to avoid it would be to use methacylate monomers. 2 Also, preliminary experiments have been carried out on multiple networks with different monomers, showing interesting properties that might be due to a local microphase separation. Further similar networks will be synthesized during the internship. Once the synthesis is completed, several characterizations of the mechanical properties will be carried out such as viscoelastic properties in small and large strain, hysteresis due to damage and fracture toughness tests. This internship is an opportunity to have a good insight in the physical chemistry of the materials. Indeed the internship will combine the synthesis and the mechanical characterization of innovative elastomers. Qualité requises Stage idéalement ciblé pour un master physico-chimie des matériaux ou SMNO Références 1. Ducrot, E., Y. Chen, M. Bulters, R. P. Sijbesma and C. Creton (2014). "Toughening Elastomers with Sacrificial Bonds and Watching them Break." Science 344(6180): 186-189.