SKM 2023 – wissenschaftliches Programm
DY 24.4: Vortrag
Dienstag, 28. März 2023, 14:45–15:00, ZEU 148
Confinement induced relaxations and phase behavior of a nanoconfined ionic liquid crystal — •Mohamed Aejaz Kolmangadi1, Andreas Schönhals1, Li Zhuoqing2, and Patrick Huber2 — 1Bundesantalt für Materialforschung und -prüfung (BAM), Berlin, Germany — 2Technical Univeristy Hamburg TUHH and DESY
We investigate the molecular dynamics and electrical conductivity of a linear shaped guanidinium based ILC confined in self-ordered nano porous alumina oxide membranes of pore size ranging from 180nm down to 25nm by employing broadband dielectric spectroscopy (BDS) and calorimetry. Calorimetric investigation reveals a complete suppression of the columnar - isotropic transition, while the plastic crystalline - columnar transition temperature decreases with inverse pore size and deviates from the Gibbs - Thomson equation. For the bulk case, BDS detects two relaxation modes in the crystalline phase, the gamma relaxation and the α1 relaxation, and two relaxation modes in the columnar phase, the α2 and α3 relaxation. For the confined case, all relaxation modes slow down compared to the bulk. However, for the least pore size (25 nm), the α2 relaxation is absent. We discuss the possible molecular origins of the different relaxation modes observed. For the bulk ILC, a clear jump of 4 orders of magnitude in the absolute values of DC conductivity occurs at the transition from the plastic crystalline to hexagonal columnar phase, for the confined ILC, this transition is smooth. DC conductivity is reduced for the confined case, except for the 25nm, where the values is similar to the bulk.