Perfectly Alternating Copolymerization of Propylene Oxide and CO₂over SalenCo/SalenCr Complexes

Abstract

Schiff-cobalt (salenCo) and Schiff-chromate (salenCr) were synthesized and used as catalysts for copolymerizing of propylene oxide (PO) and CO 2 . The alternating copolymer of polycarbonate was successfully obtained under mild conditions in the presence of 4-(dimethylamino)-pyridine (DMAP) cocatalyst. The influences of DMAP amount, polymerization time, temperature, and CO 2 pressure on the copolymerization efficiency and selectivity to polycarbonate were investigated in the presence of catalysts. Under the optimized conditions, salenCo/DMAP exhibited an excellent catalytic efficiency with perfectly alternating copolymerization products (99% carbonate and more than 99% polycarbonate with head-to-tail linkage) and high selectivity to polycarbonate over cyclic carbonate (more than 99% polymeric product) without byproduct (polyether). While only 76% selectivity to polymer, 95% carbonate linkage, and 80% head-to-tail connection unit were obtained over salenCr/DMAP catalyst. Furthermore, the catalytic activity of salenCo was superior to that of salenCr, resulting in higher molecular weight, more regular microstructure, and higher stability of copolymer.

Study of Preparation and Properties of Stereoregular Poly(cyclohexenylene carbonate)

“…All raw materials needed to be dried before use to redu moisture content. The 3,3'-diformyl-4,4'-dihydroxy-1,1'-biphenyl and salicylalde condensation product were prepared according to references [47,48], respectively their structures were confirmed by FTIR and NMR characterization (Figures S1-S6 monometallic cobalt catalysts Ia-Id used for comparison were prepared accordi references [49,50].…”

Chromium Diamino-bis(phenolate) Complexes as Catalysts for the Ring-Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide

“…Epoxides such as cyclohexene oxide (CHO) and propylene oxide (PO) are three-membered cyclic ethers with considerable ring strain, making them ideal candidates for transformation into useful materials such as cycloaddition or copolymerization with CO 2 . − Chromium coordination complexes have been shown to be catalysts for CO 2 /epoxide ring-opening copolymerization (ROCOP), − CO 2 /epoxide cycloaddition, − and ring-opening polymerization (ROP) − to produce polycarbonates, cyclic carbonates, and polyethers, respectively. One can overcome limitations to catalyst selectivity via the tuning of complex properties such as sterics, electronics, and geometry, which is commonly done by varying ligand substituents. , …”