Supercritical CO₂: solution to polymer synthesis, processing and purification

One of the major challenges in polymer production technology is developing new processes that are more sustainable, cleaner, and environmentally friendly. Since the vast majority of these processes are conducted using volatile organic solvents, research into more sustainable methods focuses on finding safer, less harmful, and non-toxic solvent alternatives. 

In his thesis, Friso Versteeg investigated the use of supercritical solvents and more specifically, supercritical CO2 (scCO2), as an alternative for polymer synthesis, processing and purification respectively. Furthermore, the bio renewable chemical α-methylene-γ-butyrolactone (α-MBL) is the key component in the polymers that are synthesized in the present work. Unique properties for α-MBL are the high glass transition temperature (Tg) of 195 °C and the excellent chemical resistance. 

Versteeg explored the possibility of replacing fossil based building blocks for the biorenewable compound (α-MBL). In the end it was deemed a success by making partly based rubbers that are comparable to commercially available synthetic rubbers such as styrene-butadiene-styrene (SBS). He also explored the use of scCO2 for polymer purification and processing. By using scCO2 as an extraction solvent bulk polymers such as poly(methyl methacrylate) and polystyrene were stripped of 99.99% of monomer impurifications making this an environmentally friendly alternative.

Finally Versteeg determined the solubility of scCO2 in polystyrene and developed a mathematical model. This was done as scCO2 can act as a foaming agent for polystyrene. The mathematical model proved to be very accurate in predicting the solubility and swelling of the polystyrene under supercritical conditions.

Dissertation: https://hdl.handle.net/11370/8a19d1bd-39a2-438f-9dd4-6d9ab816e793