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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 17: Charged Soft Matter, Polyelectrolytes and Ionic Liquids I
CPP 17.7: Talk
Tuesday, March 19, 2024, 11:30–11:45, H 0107
Polymerised ionic liquids in solutions: Conformation and rheology — •Carlos Lopez1, Atsushi Matsumoto2, Takaichi Watanabe3, and Walter Richtering4 — 1Materials Science and Engineering Department, The Pennsylvania State University, US — 2Department of Applied Chemistry and Biotechnology, University of Fukui, Japan — 3Department of Applied Chemistry, Okayama University, Japan — 4Institute of Physical Chemistry, RWTH Aachen University, Germany, European Union
We investigate the phase behaviour, solution rheology and scattering properties of a polymerised ionic liquid in over 20 different solvents. The polymer is found to be soluble in aprotic solvents of medium or high polarity, but not in protic solvents (e.g. water or ethylene glycol).
In high dielectric constant solvents, the correlation length scales as ξ ∝ C−1/2, indicating rod-like local conformations. For solvents with modest dielectric permittivities (є ≃ 18 - 30), the correlation length scales as ξ ∝ C−1/3, suggesting a partially collapsed pearl-necklace conformation. We hypothesise that the collapsed conformation arises from the influence of dipolar attraction from condensed counterions. In THF (є = 8), the scattering pattern follows the Ornstein-Zernike pattern, similar to neutral polymers.
Viscosity data display the exponents predicted by the scaling theory of Dobrynin et al. However, the ratio ηsp/(Cξ3) depends on the solvent type, in contradiction to the scaling model. Our results provide a framework to understand the influence of electrostatics and solvation forces on the structure of polyelectrolytes.
Keywords: Polyelectrolyte; Ionic liquid; scattering; rheology; phase behaviour