RAFT enables controlled radical ring-opening polymerisation of cyclic ketene acetals for degradable nanoparticles.

Following the demand for biodegradable polymers in biomedicine and cosmetics, the radical ring-opening polymerisation (RROP) of cyclic ketene acetals (CKAs) offers a robust synthesis approach to prepare a wide range of polyesters. Here we demonstrate a method to control the RROP of 2-methylene-1,3,6-trioxocane (MTC) in terms of molar mass, dispersity, end-group control and kinetics using the reversible addition and fragmentation chain transfer polymerisation (RAFT) methodology. Fine-tuning the ratio between the reactants allows for a better understanding of the interplay of RAFT and RROP. With so optimised reaction conditions, a well-defined PMTC-macroinitiator was obtained and a chain extension with MTC and 2-methylene-1,3-dioxepane (MDO) was applied to form P(CKA-b-CKA) block copolymers. These were then formulated into fully biodegradable polymeric nanoparticles with tuneable degradation time. This work hence pushes the boundaries of RROP towards a whole expanded range of defined homopolymers and fully CKA-based block-copolymers as well as their completely biodegradable nanoparticles. This controlled RROP opens more areas of application for RROP-based polyesters.