Tailoring length and viscosity of dynamic metallo-supramolecular polymers in solution

Abstract

Transition metal ions, like Fe²⁺, Co²⁺ and Ni²⁺ coordinate to ditopic ligands such as 1,4-bis(2,2′:6′,2′′-terpyridin-4′-yl)benzene (1) forming sufficiently strong yet dynamic bonds in aqueous solutions, leading to extended, rigid-rod like metallo-supramolecular coordination polyelectrolytes (MEPEs). Here, we present a way to adjust the average molar mass, chain-length and viscosity of MEPEs using the monotopic chain stopper 4′-(phenyl)-2,2′:6′,2′′-terpyridine (2). The systems are analyzed by light scattering and viscometry. The experiments indicate that chain-length and viscosity of the MEPEs are modifiable in predictable ways by adding the monotopic chain stopper, 2. Light scattering is a suitable method for studying the molar mass and also the shape of the MEPEs.