FUNCTIONAL POLYMER LABORATORY

One of our initial studies involved the utilization of this approach for the synthesis of linear conjugated metallopolymers, which feature ease of processing and good mechanical properties and may synergistically combine functionalities of conjugated core and the metal ions employed. We utilized this approach, for example, for the polymerization of a conjugated macromonomer that was derived by functionalizing a low-molecular weight PPE core with 2,6-bis(1’-methyl-benzimidazolyl)pyridine (Mebip) ligands on the two terminal positions. We demonstrated that the supramolecular polymerization of this macromonomer with equimolar amounts of metal ions such as Zn²⁺ or Fe²⁺ results in materials which exhibit appreciable mechanical strength, but due to their dynamic, reversible nature offer the ease of processing of low-molecular weight compounds.

Arylene alkylene metallopolymers are another example for a class of metallopolymers investigated in our laboratory. The materials are based on a poly(2,5-dialkoxy-p-xylylene) macromonomer that was derived by functionalizing a low-molecular weight poly(p-2,5-dialkoxy phenylene ethynylene) core with 2,6-bis(1’-methyl-benz­imida­zolyl)­pyridine (Mebip) ligands on the two terminal positions and subsequent reduction under Hahn diimide conditions. The supramolecular polymerization of this macromonomer with equimolar amounts of Zn²⁺ or Fe²⁺ and a small amount of La³⁺, which can bind three Mebip ligands and causes cross-linking and/or branching, resulted in polymers which offer the ease of processing of low-molecular weight compounds and the exhibit excellent mechanical properties and high temperature stability of poly(arylene akylene)s.

Exploiting that the fluorescence of the certain (macro)ligands changes upon metal binding and that certain metals have a strong, sometimes rather selective binding affinity to analytes of interest, we embarked on a study that utilizes this chemical framework for the development of Fluorescent Sensory Systems that function on the basis of Competitive Binding. In a recently published manuscript, we reported the development of a modular sensory system which utilizes a multi-metal/multi-ligand based approach. The judicious design of fluorescent ligands and the careful selection of metal/ligand combinations allowed us to create a very simple sensor platform that appears to allow the selective detection of aliphatic organophosphates (toxic species commonly found in both pesticides and chemical warfare agents) with good sensitivity and can be readily adapted for many other analytes of interest.

Schematic representation of the formation of a metallo-supramolecular polymer.

Chemical structures of macromonomers based on Mebip ligands and PPE (top) or PPX (bottom) core.

Film produced by metallo-polymerization of  PPE-Mebip macromonomers (see above) with the above with Zn²⁺.

Schematic representation of  fluorescent sensory schemes that exploit competitive binding.