Metal-Free Approach for a One-Pot Construction of Biodegradable Block Copolymers from Epoxides, Phthalic Anhydride, and CO2

Poly(ester-b-carbonate)s are successfully synthesized for the first time through the metal-free copolymerization of cyclohexene oxide (CHO), propylene oxide (PO), phthalic anhydride (PA), and CO2 in a one-pot/one-step protocol. Catalyzed by triethyl borane (TEB) and bis(triphenylphosphine)iminium chloride (PPNCl) Lewis pair, the diblock and triblock copolymers with little tapering are synthesized from the initiation of PPNCl and phthalic acid, respectively. Copolymers with a high molecular weight of up to 50 kDa can be readily obtained under mild conditions. By changing the content of chain components in quadripolymers, glass transition temperature (T-g) values are adjusted between 86 and 115 degrees C. Moreover, the products appear extremely transparent with transparency of above 85% in the range of 600-1000 nm. This work first focuses on the synthesis of quadripolymers with high T(g)s (>90 degrees C) and tensile strength (up to 54.8 MPa), which have similar thermal, mechanical properties, and transparency as those of commercial polystyrene and thus may be candidate green materials to replace the nondegradable polystyrene in extensive application areas.