Dielectric spectroscopy in polymer science : from glassy dynamics to supramolecular associations p to isolated molecules

Le 29 mai 2018
À 10h30
Amphi HENRI BENOÎT (ICS)

Vous êtes cordialement invités au séminaire de Martin TRESS ddu Department of Chemistry, University of Tenessy Knoxville, USA, organisé par l'Institut Charles Sadron.

Présentation du séminaire :
Dielectric spectroscopy has proven a versatile tool in polymer research offering direct access to structural dynamics in a wide frequency and temperature range. I will introduce this method and present 3 projects where it provided detailed insight on molecular scale. The first part focusses on a semi-crystalline star-shaped polymer based on a central (POSS) molecule [1] connected to isotactic polystyrene (iPS) arms. While linear iPS has restricted segmental mobility around crystallites, the POSS-iPS star exhibits faster dynamics in the semi-crystalline state [2], an unexpected crystallization-induced confinement effect probably due to the uncommon chain architecture. The second part addresses supra-molecular networks of telechelic polymers with different hydrogen-bonding end-groups. We find quite opposing dependencies of glass transition temperature and viscosity on the H-bond strength for polydimethyl siloxanes and polypropylene glycol [3,4]. Complementary measurements of shear modulus and dielectric spectroscopy indicate that this can be explained by competing lifetimes of the supra-molecular associations and the structural relaxations. This molecular picture, yet qualitative, can eventually help us derive design principles for related materials to optimize e.g. self-healing. The third part presents a nano-structured electrode setup which enables dielectric measurements of extremely small samples like nanometer-thin polymer layers and individualized polymer chains [5]. This demonstrates how dielectric spectroscopy can be used to study isolated molecules (yet averaging over large numbers of them) at surfaces in a much wider frequency range than common single molecule techniques.
[1] Vielhauer, M.; Lutz, P. J.; Reiter, G. & Mülhaupt, R. J Polymer Sci Part A: Polymer Chem, 2013, 51, 947
[2] Tress, M.; Vielhauer, M.; Lutz, P. J.; Mülhaupt, R. & Kremer, F. Macromolecules, 2018, 51, 501
[3] Xing, K.; Tress, M.; Cao, P.; Cheng, S.; Saito, T.; Novikov, V. N. & Sokolov, A. P. Soft Matter, 2018, 14, 1235
[4] Xing, K.; Tress, M.; Cao, P.; Cheng, S.; Saito, T.; Novikov, V. N. & Sokolov, A. P. (in preparation)
[5] Tress, M.; Mapesa, E. U.; Kossack, W.; Kipnusu, W. K.; Reiche, M. & Kremer, F. Science, 2013, 341, 1371
Les personnes souhaitant rencontrer Martin Tress sont priées de prendre contact avec Pierre Lutz (tel. 03 88 41 40 74 ou mail pierre.lutz@ics-cnrs.unistra.fr)

Habilitations
Label du Ministère de l'enseignement supérieur, de la recherche et de l'innovation CTI - Commission des Titres d'Ingénieur EUR-ACE® system - European Accreditation of Engineering Programmes Université franco-allemande Certification AFAQ - ISO 9001 IAR Label DD&RS
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