From Vesicles to Cylinders in MeBIP-containing Poly(acrylate)s

Supramolecular assembly of metallopolymers provides a wide parameter space in which morphology can be altered, without additional polymer synthesis, whether by changing the metal salt, adding free metal-ligand complex, or by addition of other compounds. Here, we have explored morphological behavior in a system based on a low molecular weight prepolymer of poly(n-butyl acrylate) containing 2,6-bis(1′-methylbenzimidazolyl)pyridine (MeBIP) -functionalized acrylate, synthesized using controlled radical techniques. MeBIP accounted for 2 to 10 percent of the prepolymer. Supramolecular assembly of the prepolymer by addition of Zn(ClO₄)₂ salt produced free-standing networked films. In most cases, an essentially amorphous and featureless material resulted. In one case, however, vesicles containing concentrated metal-ligand complex were observed. When small amounts of free MeBIP-salt complex were added to these materials supramolecular assemblies, a change in morphology from vesicles to cylinders was observed. Morphological behavior was monitored using small-angle X-ray scattering (SAXS), and probed extensively using high-angle annular dark field scanning TEM (HAADF STEM), energy dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and energy filtered TEM (EFTEM).