Thursday 11. October 2018
Anton Mordvinkin on “Multi-technique characterization of ionic elastomers: structure, molecular dynamics, and self-healing kinetics”
Von-Danckelmann-Platz 3, SR 1.03
06120 Halle (Saale)
Time: 3.30pm - 5.00pm
Link to Google-Maps
Multi-technique characterization of ionic elastomers: structure, molecular dynamics, and self-healing kinetics
A multi-technique characterization of structure and dynamics of self-healing entangled ionomeric networks prepared by modification of commercial bromobutyl rubber (BIIR) with alkylimidazoles differing with the length of the alkyl group is presented. Structural and morphological analyses, conducted by small-angle X-ray scattering (SAXS) and NMR relaxometry, show that ionic groups are mostly in the closed state and form ionic multiplets with aggregation numbers of around 20 ionic groups, which does not lead to an appreciable chain immobilization and phase separation. The molecular dynamics of network chains and ionic cross-links as measured by 1H multiple-quantum (MQ) NMR at low and high resolution, respectively, accelerates with the length of the alkyl group. Using a recently introduced fitting model, the bond lifetimes and activation energies of ionic dissociation can now be quantified by 1H MQ NMR. The correlation of the results of MQ NMR and dynamic mechanical analysis (DMA) showed a good agreement in the extracted activation energies, whereas the discrepancies in the found bond lifetimes suggest the necessity of redefining the bond lifetimes found by DMA to shorter time scales with respect to the maximum of the loss modulus. The mechanical experiments in the non-linear regime reveal a dynamic character of the studied ionic networks, defined by the relationship between the initial deformation rate and the DMA’s bond lifetime, show a decrease in the bond lifetimes with disintegration of the ionic networks upon stretching and demonstrate self-healing ability.