Rigid, Helical Arm Stars through Living Nickel Polymerization of Carbodiimides

Using the core-first growth strategy, we have synthesized a tris-Ni­(II) initiator which bears three initiating sites for the ensuing polymerization of N-1-phenethyl-N′-methyl­carbodiimide. The arms of these star polymers bearing chiral side chains adopt single-handed helical rod-like conformations. The polymerization occurs in a controlled, living fashion, and this multiarm architecture imparts a new set of intriguing properties including their self-assembly into diverse nanostructures when cast from different solvents. These assemblies, characterized by AFM, TEM, and DLS, include the formation of nanofiber networks and twisted superhelical nanostructures. Interestingly, by processing these polymers via electrospraying method, hollow and uniform platelet-like particles were obtained. These solvent-dependent morphologies of microparticles were observed by using SEM. The kinetic studies of polymerizations, inspection of self-aggregation behaviors, and electrosprayed architectures will open up possibilities for a variety of potential biomedical applications.