Architecture-Controlled Synthesis of Redox-Degradable Hyperbranched Polyglycerol Block Copolymers and the Structural Implications of their Degradation

Abstract

We have successfully synthesized a series of redox-degradable 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 H-1 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.