Supercritical CO₂ as an Efficient Medium for Macromolecular Carbonate Synthesis through Ring-Opening Co- and Teroligomerization

Abstract

Ring-opening polymerization and teroligomerization processes that involve two different epoxides and carbon dioxide are significantly more efficiently executed in a supercritical CO2 medium. Here, we demonstrate that this generally considered green medium is advantageous for the catalytic formation of both conventional and biobased co- and teroligomers avoiding the occurrence of diffusion-limited catalysis while maximizing the polymer quality, yield, and carbonate content.

Bicyclic Guanidine Promoted Mechanistically Divergent Depolymerization and Recycling of a Biobased Polycarbonate

“…We also examined three other types of polycarbonates and subjected these to the same conditions as used for the experiments discussed in Schemes 2 and 3 using a reaction time of 7 h. When PCHC is used as a substrate (Scheme 5, top), depolymerization promoted by TBD only yields the trans‐ CHC (95 %) as product in line with observations from Williams and Buchard [11e] . We then turned to mixed, terpolymeric carbonates with repeat units based on LO and CHO, and LO and Me CHO, respectively [19] . The carbonate repeat units based on CHO (72 %) were degraded with a similar product profile as seen with PCHC, while the repeat units based on LO (28 %) gave a mixture of the epoxide and cyclic carbonate.…”

Bicyclic Guanidine Promoted Mechanistically Divergent Depolymerization and Recycling of a Biobased Polycarbonate

“…[11e] We then turned to mixed, terpolymeric carbonates with repeat units based on LO and CHO, and LO and Me CHO, respectively. [19] The carbonate repeat units based on CHO (72 %) were degraded with a similar product profile as seen with PCHC, while the repeat units based on LO (28 %) gave a mixture of the epoxide and cyclic carbonate. For the terpolymer that is derived from two different trisubstituted epoxide (LO and Me CHO), a similar product profile is noted as for the catalytic degradation of PLC, with the major constituent of the reaction mixture being the combined trans cyclic carbonates (67 %).…”

High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics

“…It is recommended for further development as a thermoplastic and may inspire the investigation of other substituted cyclohexane rings. Given that using bioderived epoxides may also help increase carbon dioxide uptake, terpenes such as limonene or menthene also feature substituted cyclohexane rings and their epoxides have precedent in this catalysis. ,− Limonene oxide is challenging to polymerize due to its tertiary structure, , but menth-2-ene oxide is an important future target given the influence in this work of ethyl substituents . Greiner and Agarwal reported a route to prepare moderate molar mass poly­(meth-2-ene carbonate) ( M n = 20–30 kg mol –1 ), and the polymer showed a higher glass transition temperature ( T g = 144 °C) and higher temperature stability ( T d = 308 °C) than PCHC .…”