Green chain-shattering polymers based on a self-immolative azobenzene motif

Abstract

A chain-shattering polymer system consisting of nontoxic, renewable resource-based monomers via acyclic diene metathesis (ADMET) chemistry is introduced. Amphiphilic triblock copolymers with apparent molecular weights in the range from 10 to 23 kDa are synthesized using a monofunctional polyethylene glycol monoacrylate, which acts as a selective chain-transfer agent during the polymerization process. Most importantly, the functional polymers possess repetitive midchain azobenzene moieties imparting them with self-immolative properties. By virtue of the enzyme degradable azobenzene chain elements, the amphiphilic macromolecules can be efficiently degraded via a self-immolative reaction into small fragments. The construction of the macromolecules along with their degradation is evidenced by nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry and size exclusion chromatography. In addition, the triggered degradation leads to a strong reduction in the UV absorptivity of the polymeric material.