We have successfully synthesized a series of redoxdegradable hyperbranched polyglycerols using a disulfide containing monomer, 2-((2-(oxiran-2-ylmethoxy)ethyl)disulfanyl) ethan-1-ol (SSG), to yield PSSG homopolymers and hyperbranched block copolymers, P(G-b-SSG) and P(SSG-b-G), containing nondegradable glycerol (G) monomers. Using these polymers, we have explored the structures of the hyperbranched block copolymers and their related degradation products. Furthermore, side reaction such as reduction of disulfide bond during the polymerization was investigated by employing the free thiol titration experiments. We elucidated the structures of the degradation products with respect to the architecture of the hyperbranched block copolymer under redox conditions using 1 H NMR and GPC measurements. For example, the degradation products of P(G-b-SSG) and P(SSG-b-G) are clearly different, demonstrating the clear distinction between linear and hyperbranched block copolymers. We anticipate that this study will extend the structural diversity of PG based polymers and aid the understanding of the structures of degradable hyperbranched PG systems.

Owing to the unique advantages of combining the characteristics of hydrogels and nanoparticles, nanogels are actively investigated as a promising platform for advanced biomedical applications. In this work, a self-cross-linked hyperbranched polyglycerol nanogel is synthesized using the thiol-disulfide exchange reaction based on a novel disulfide-containing polymer. A series of structural analyses confirm the tunable size and cross-linking density depending on the type of polymer (homo- or copolymer) and the amount of reducing agent, dithiothreitol, used in the preparation of the nanogels. The nanogels retain not only small molecular therapeutics irrespective of hydrophilic and hydrophobic nature but also large enzymes such as β-galactosidase by exploiting the self-cross-linking chemistry. Their superior biocompatibility together with the controllable release of active therapeutic agents suggests the applicability of nanogels in smart drug delivery systems.