Biomimetic Polymer Models for Natural and Synthetic Soft Matter

Amanda Marciel from Rice University
Cemo 100D

Polyelectrolyte complexes are highly tunable materials that span from low--‐‑viscosity liquids
(coacervates) to high--‐‑modulus solids with high water content, making them attractive as surface
coating, membrane purification and bioadhesive materials. However, most of their properties
and their effects with salt, pH, polymer ratio and temperature have only been qualitatively
described. Here, we present an investigation of the structure and chain conformations, and
rheological properties of polyelectrolyte complex (PEC) coacervates comprising biomimetic
model polyelectrolytes. Systematic studies using small--‐‑angle X--‐‑ray scattering (SAXS) of the
structure and chain behavior in liquid PEC coacervates revealed a physical description of these
materials as strongly screened semidilute solutions of polyelectrolytes comprising oppositely
charged chains. At the same time, solid PECs were found to be composed of hydrogen--‐‑bonding
driven stiff ladder--‐‑like structures with large correlation lengths. While the liquid complexes
behaved akin to semidilute polyelectrolyte solutions upon addition of salt, the solids were largely
unaffected by it. Terminal relaxations of the chains in PEC coacervates were explored by
rheology measurements. Excellent superposition of the dynamic moduli data was achieved by a
time--‐‑salt superposition.