Reduction-cleavable hyperbranched polymers with limited intramolecular cyclization via click chemistry

In this contribution, we present new reduction-cleavable hyperbranched disulfide bonds-containing poly(ester triazole)s with limited intramolecular cyclization, which can be synthesized by the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) of A₂ monomer of dipropargyl 3,3′-dithiobispropionate and B₃ monomer of tris(hydroxymethyl)ethane tri(4-azidobutanoate). The hyperbranched poly(ester triazole)s possess numerous terminal groups and weight-average molecular weight up to 20,400 g mol^-1 with a polydispersity index in the range 1.57-2.17. The CuAAC introduces rigid triazole units into the backbones of hyperbranched poly(ester triazole)s and reduces intramolecular cyclization, which is proved by topological analysis and ¹H NMR spectroscopy. The disulfide bonds on backbones endow the reduction-cleavable feature to the hyperbranched poly(ester triazole)s at the presence of dithiothreitol. It gives a novel and convenient methodology for the synthesis of reduction-responsive functional polymer with controlled topologies, and the reduction-cleavable hyperbranched poly(ester triazole)s with limited intramolecular cyclization are expected to possess potential in the application of stimuli-responsive anticancer drug nanocarriers.