ma0c00876_si_001.pdf (5.12 MB)
Structure–Property Relationships of Microphase-Separated Metallosupramolecular Polymers
journal contribution
posted on 2020-07-01, 21:37 authored by Laura
N. Neumann, Ilja Gunkel, Amber Barron, Emad Oveisi, Albrecht Petzold, Thomas Thurn-Albrecht, Stephen Schrettl, Christoph WederThe
structural, thermomechanical, and viscoelastic properties of
metallosupramolecular polymers (MSPs) can be controlled through the
choice of the multiligand monomer and the nature of the metal salt
from which these materials are assembled. This versatility and the
dynamic nature of certain metal–ligand (ML) complexes make
MSPs very interesting for the design of stimuli-responsive materials.
We here report on the investigation of the structure–property
relationships of MSPs based on a macromonomer formed by terminating
telechelic poly(ethylene-co-butylene) (PEB) with
2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip)
ligands and transition metal or lanthanoid salts. The nature of the
metal ion (Zn2+, Fe2+, Tb3+, La3+, or Gd3+), the counterion (trifluoromethanesulfonate
(OTf–), perchlorate (ClO4–), or bis(trifluoromethylsulfonyl)imide (NTf2–)), and the number-average molecular weight (Mn) of the PEB core (2100 or 3100 g mol–1) were systematically varied with the aim to provide an improved
understanding of how these parameters influence the properties. In
all MSPs, the polar ML complexes and the nonpolar PEB were found to
microphase separate into lamellar or hexagonal morphologies with a
soft PEB phase and a ML hard phase. The microstructure formation and
the mechanical properties were significantly influenced by the coordination
geometry of the metal–ligand complexes as well as the volume
fraction of the ML phase. The nature of the metal and counterions
further affected the glass or melting transitions of the hard phase.
In general, lower softening temperatures were observed for the MSPs
made with lanthanoid salts. Measurements of the frequency-dependent
oscillatory shear moduli were used to study the relaxation processes
in the different MSPs and allowed determining the activation energy
of the ML complexes in lanthanoid-based MSPs.