The viscosity and diffusion coefficient of polymers are two of the most important parameters for applications and processing. Scaling relationships as a function of degree of polymerization (N) are well-characterized in neutral polymers, but many current and emerging applications in polymer science involve ionic charges including electrolytes, coacervates, and membranes.  We have synthesized fluorescently-labeled polymerized ionic liquids (f-PILs) with a broad range of molecular weights to understand scaling relationships in dry, ionic polymers with a charge on every repeat unit. Fluorescence recovery after photobleaching (FRAP) is used to measure polymer self-diffusion coefficients (<i>D</i>) using the post-bleached fluorescence images and fitting the intensity to a Gaussian profile over time. The zero-shear viscosity was measured via rheology. In the shortest f-PILs, the ionic interactions between imidazolium and bis(trifluoromethane sulfonamide) have little effect on extending the terminal regime. However, the terminal region did extend to lower frequencies as N increased. Interestingly, the wide-angle x-ray scattering shows an amorphous halo and anion-anion peak, but no longer range ionic aggregate peak which we assign as the origin of the rheological behavior. Scaling relationships show the same dependence, 1/N, as in neutral polymers in contrast to some literature reports. Diffusion coefficient scaling will also be discussed.

Understanding viscosity-scaling relationships of highly charged, anhydrous ionic polymers

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.