Oxidation‐Responsive Aliphatic Polycarbonates from N ‐Substituted Eight‐Membered Cyclic Carbonate: Synthesis and Degradation Study

Oxidation‐responsive aliphatic polycarbonates represent a promising branch of functional biodegradable polymers. This paper reports the synthesis and ring‐opening polymerization (ROP) of an eight‐membered cyclic carbonate possessing phenylboronic pinacol ester ( C3 ) and the H 2 O 2 ‐triggered degradation of its polymer ( PC3 ). C3 is prepared from the inexpensive and readily available diethanolamine with a moderate yield and undergoes the well‐controlled anionic ROP with a living character under catalysis of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene. It can also be copolymerized with l ‐lactide, trimethylene carbonate, and 5‐ ter ‐butyloxycarbonylamino trimethylene carbonate, affording the copolymers with a varied distribution of the repeating units. To clearly demonstrate the oxidative degradation mechanism of PC3 , this paper first investigates the H 2 O 2 ‐induced decomposition of small‐molecule model compounds by proton nuclear magnetic resonance ( 1 H NMR). It is found that the adduct products formed by the in‐situ‐generated secondary amines and p ‐quinone methide (QM) are thermodynamically unstable and can decompose slowly back to QM and the amines. On this basis, this paper further studies the H 2 O 2 ‐accelerated degradation of PC3 nanoparticles that are prepared by the o/w emulsion method. A sequential process of oxidation of the phenylboronic ester, 1,6‐elimination of the in‐situ‐generated phenol, releasing CO 2 and intramolecular cyclization or isomerization is proposed as the degradation mechanism of PC3 .