On the formation and electropolymerization of a star copolymer with peripheral carbazoles

Utilizing a hyperbranched cored ring-opening polymerization of caprolactone, carbazole peripheral groups are extended to afford electropolymerizable star-like copolymers. Different arm lengths are obtained on the basis of different degrees of polymerization from the polyethyleneimine core. This is confirmed by NMR and Fourier transform IR (FTIR) spectroscopy, size-exclusion chromatography (SEC), and quantitative spectral characterization. Atomic force microscopy (AFM) imaging shows two distinct particle aggregation characteristics, before and after functionalization with carbazole groups. Cyclic voltammetry verifies the electrochemical cross-linking properties. The results indicate that the conformational freedom of the electroactive peripheral functional groups can be controlled. Moreover, an interesting "loop effect" together with solid-state polymerization is observed. Star copolymers have unique structural features closest to fixed micelles. On the other hand, they can also be considered to be an extension of dendrimers in terms of peripheral-group functionality. This concept is demonstrated in functionalizing electropolymerizable carbazole functional groups in star copolymers of polycaprolactone with a polyethyleneimine (PEI) dendrimer core. In essence, these are hybrid architectures that demonstrate the particle nature of polymers.