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

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.