Interrupted CuAAC Ligation: An Efficient Approach to Fluorescence Labeled Three-Armed Mikto Star Polymers

Abstract

We introduce a powerful variant of the copper(I)-mediated azide–alkyne cycloaddition (CuAAC) for the synthesis of miktoarm block copolymers with a fluorescently labeled core. Via the simple addition of a functional azirine to a conventional CuAAC reaction of an azide and alkyne terminal polymer strand, a vinyl functionality is introduced at the focal point of the two polymers, which can subsequently be modified, via, e.g., radical thiol–ene addition. Concomitantly, a second functionality–a pyrene chromophore–stemming from the functional azirine is introduced enabling fluorescence detection and unimolecular micelle formation. Thus, by virtue of thiol terminal polymers an efficient two-step synthesis of midchain functional mikto-three armed star polymers is possible. Detailed NMR, SEC, DSC, UV–vis, and fluorescence studies underpin the successful formation of the functional miktoarm star with a fluorescence labeled core. Finally, yet importantly, dynamic light scattering (DLS) results demonstrate that the miktoarm polymers form self-fluorescent micelles in aqueous media and display robust micellar stability with unimolecular micellar characteristics.