Doctoral students seminar (October 22, 2019)

Polymer chains with covalently bonded supramolecular groups can build dynamic networks through establishment of supramolecular interactions. This ability paves new ways for potential applications as stimuli-responsive and sustainable materials in different areas such as automotive and aerospace inductries, biomedicine, biorobotics, etc. Properties of these materials can be easily tuned by changing various molecular parameters related to polymer chains and supramolecular groups. Mechanical properties and stimuli-responsiveness are determined by molecular dynamics coupling segmental and supramolecular dynamics.

To better understand the influence of different molecular parameters on the overall dynamics, a new analytical approach based on solid-state NMR results is developed. The new approach can quantify chain dynamics in supramolecular systems on a microscale, giving relaxation times and activation energies. This enables checking of validity of various theoretical models predicting dynamics in supramolecular polymer networks, which was not possible before.

Two sets of samples are investigated, each of which forms a network of interconnected micelles with large aggregation numbers. The first set of samples includes unentangled telechelic hydrogen-bonded polyisobutylene (PIB) chains with variable molecular architecture, molecular weight, and hydrogen-bonding moiety. The second set of samples in turn encompasses entangled PIBs cross-linked with ionic alkylimidazolium groups introduced along the chain. The dynamics of the second set is tuned by variation of the length of the alkyl group in the alkylimidazolium moiety. All the samples are characterized by SAXS, rheology, solid-state NMR, and dielectric spectroscopy to obtain a full structural and dynamic picture.