Intramolecular Cyclization for Stimuli-Controlled Depolymerization of Polycaprolactone Particles Leading to Disassembly and Payload Release

Polymers capable of on-demand, controlled depolymerization are an important tool in a broad variety of applications in science, technology, and industry. We report functionalized poly(caprolactone)s (PCL)s designed to allow on-demand and complete depolymerization through incorporation of pendant protected amino groups that, on deprotection, trigger nucleophilic attack and yield a single cyclic product. Two cleavable protecting groups were used to cap PCL: light sensititve o-nitrobenzyl alcohol (ONB) and tert-butyl carbamate (Boc; for proof of concept). NMR confirmed that PCL-Boc degrades completely into the designed intramolecular cyclization products within a day upon deprotection. TEM visualization of irradiated particles made from PCL-ONB encapsulating iron oxide nanoparticles reveals complete disruption of nanoparticles and release of payload. This work demonstrates that intramolecular cyclization within the polymer backbone is an excellent route to accelerate polymer degradation by backbiting reactions into small fragments that should be easily cleared from the circulation.