A Direct Route to Cyclic Organic Nanostructures via Ring-Expansion Metathesis Polymerization of a Dendronized Macromonomer

摘要

Controlling polymer topology presents challenging synthetic obstacles as well as exciting opportunities for tuning macromolecular properties. In particular, nanoscale molecular architectures with well-defined shapes and dimensions may provide significant advancements in areas such as drug delivery and nanotechnology. Over the past decade, breakthroughs in polymer syntheses have greatly increased the variety of macromolecular architectures that may be obtained, including dendronized, cylindrical, star, hyperbranched, and cyclic polymers as well as various block copolymers. However, the synthesis of circular nanostructures remains challenging due in large part to the difficulty in preparing functionalized cyclic polymers. Furthermore, reliance on macrocyclization routes to cyclic polymers restricts attachment of large side chains or dendrons to postpolymer-ization, and an efficient route to cyclic hybrid architectures of high purity is yet to be realized. Following recent developments in ring-expansion metathesis polymerization (REMP) and linear dendronized polymers, we aimed to interface these two areas to achieve a direct, efficient route to cyclic organic nanostructures. Herein, we report the REMP of a dendronized macromonomer (MM) as well as confirmation of cyclic polymer topology via atomic force microscopy (AFM).