Star polymers are an interesting class of macromolecules possessing polymeric arms extending radially from a core center. In our growth from strategy, the core can be synthesized by incorporating multiple initiating sites for the polymerization of carbodiimides taking advantage of the recently reported Ni(II) mediated living polymerization. When incorporating chiral side chains, these star polymers are produced possessing single-handed helical, rod-like polycarbodiimide arms. The star architecture imparts a new set of intriguing properties that include self-assembly in different solvents and liquid crystallinity. Here, we report synthesis of a star polymer by using core-first method. The initiating core can be synthesized via trimerization of 3-methyl-4-bromobenzonitrile to yield a triazine ring with three aryl bromide initiating groups. In the presence of triphenylphosphine, the nickel(0) center of bis(1,5-cyclooctadiene) nickel(0) (Ni(COD)<sub>2</sub>) will undergo oxidative addition into aryl bromide bond to yield a core with three [bis(triphenylphosphino)aryl]nickel(II)bromide complex in its periphery. Exposed to carbodiimides, the tris-Ni initiators grow helical arms in a controlled fashion. The preparation of these helical stars and their solution and solid-state characterization by tapping-mode atomic force microscopy (TM-AFM), powder X-ray diffraction (XRD), electronic circular dichroism (ECD), vibrational circular dichroism (VCD), differential scanning calorimetry (DSC) and dynamic light scattering (DLS) will be discussed.

Preparation of helical star polymers using tris-nickel Initiators

249th National Meeting (2015)

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