A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. The copolymerization of cyclohexene oxide (CHO) and carbon dioxide (CO 2 ) was carried out under supercritical CO 2 (scCO 2 ) conditions to afford poly (cyclohexene carbonate) (PCHC) in high yield. The scCO 2 provided not only the C1 feedstock but also proved to be a very efficient solvent and processing aid for this copolymerization system. Double metal cyanide (DMC) and salen-Co(III) catalysts were employed, demonstrating excellent CO 2 /CHO copolymerization with high yield and high selectivity. Surprisingly, our use of scCO 2 was found to significantly enhance the copolymerization efficiency and the quality of the final polymer product. Thermally stable and high molecular weight (MW) copolymers were successfully obtained. Optimization led to excellent catalyst yield (656 wt/ wt, polymer/catalyst) and selectivity (over 96% toward polycarbonate) that were significantly beyond what could be achieved in conventional solvents. Moreover, detailed thermal analyses demonstrated that the PCHC copolymer produced in scCO 2 exhibited higher glass transition temperatures (T g 114 8C) compared to polymer formed in dense phase CO 2 (T g 77 8C), and hence good thermal stability. Additionally, residual catalyst could be removed from the final polymer using scCO 2 , pointing toward a green method that avoids the use of conventional volatile organic-based solvents for both synthesis and work-up.

High temperature melts or use of organic solvents are not practicable approaches for encapsulating protein based or thermally labile drugs into degradable polymers. Here, we demonstrate that poly(ethylene glycol) (PEG) in combination with supercritical carbon dioxide (scCO2) can dramatically reduce the viscosity of polymer melts allowing enhanced uptake of CO2 into poly(D,L-lactide) (PLA). Both PEG and CO2 are approved excipients in drug delivery and it is well documented that individually both are effective plasticisers. Using high pressure rheology techniques (scCO2 at 14 MPa) we demonstrate a synergistic impact leading to significantly lower processing temperatures with PEG employed as both a blended additive and as a component of a block copolymer.