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

Abstract

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 1H NMR in order to clearly demonstrate the degradation mechanism of the PCs. The results of 1H 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.