Supercritical CO2 antisolvent precipitation from biocompatible polymer solutions: A novel sustainable approach for biomaterials design and fabrication

• scCO2 antisolvent precipitation of polycaprolactone and polyethylene oxide is carried out.
• Ethyl lactate (EL) and ethyl acetate (EA) are used as biocompatible solvents.
• Different solid-state polymer forms are obtained by tuning the operating conditions.
• Polymer crystallization in scCO2 depends on solvent choice and polymer concentration.
• In certain conditions, CO2 induces melting and recrystallization of the precipitate.

Supercritical CO2 (scCO2) is used as an antisolvent to assist the precipitation of poly(ɛ-caprolactone) (PCL) and poly(ethylene oxide) (PEO) from biocompatible solvents such as ethyl lactate (EL) and ethyl acetate (EA). Compared to precipitation by standard air-drying methods, through which a limited number of polymer structures can be achieved, the use of scCO2 offers the opportunity to tune the solid-state morphology of the material, which may assume the form of continuous films, discrete precipitates and/or porous microparticles, possibly passing from one to other by adjusting the temperature, pressure and solution composition. The crystalline structure and surface texture of the samples are assessed by means of optical, electron and confocal microscopy. Under certain conditions, scCO2 is found to plasticize the polymer, promoting partial or complete recrystallization phenomena and eventually giving rise to bimodal spherulite size distributions.

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