Oxidation-Promoted Degradation of Aliphatic Poly(carbonate)s via Sequential 1,6-Elimination and Intramolecular Cyclization

We report a new type of oxidation-promoted fast-degradable aliphatic poly(carbonate)s (PCs) prepared by the ring-opening polymerization (ROP) of a six-membered cyclic carbonate containing a phenylboronic pinacol ester. The ROP of this monomer catalyzed by 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) proceeded rapidly at ambient temperature with a good control over molecular weight and polydispersity at high monomer conversion. The H2O2-induced decomposition of this cyclic monomer and its noncyclic carbonate analogue was first studied by H-1 NMR in order to clearly demonstrate the degradation mechanism of the PCs. The results of H-1 NMR, GPC, and Nile Red fluorescence measurements revealed that the PC nanoparticles formulated by the o/w emulsion method were stable in neutral buffer, but upon triggering with H2O2, they underwent rapid surface degradation via the consecutive processes of oxidation, 1,6-elimination, release of CO2, and intramolecular cyclization. The degradation rates of the nanoparticles were dependent on the concentration of H2O2, and the nanoparticles were even sensitive to 0.5 mM of H2O2.