Switchable Solvents for the Reversible Dissolution of Poly(3-hydroxybutyrate)

High Resolution Image Download MS PowerPoint Slide The biopolymer poly(3-hydroxybutyrate) (PHB) is an excellent candidate to replace many petroleum-sourced polymers for a wide range of applications. Improving PHB recovery and processing methods remains an important step toward expanding its implementation and economic viability. Switchable solvents are a class of molecules that can be toggled between hydrophobic and hydrophilic forms through the addition of carbon dioxide and water, which makes them promising candidates as recyclable solvents for the recovery of bioproducts such as PHB. Here, we used the Hansen solubility parameters and the Stefanis–Panayiotou group contribution method to select candidate switchable solvents for processing PHB. We evaluated their ability to dissolve PHB over a range of temperatures and found that the theoretical methods accurately predicted interactions between PHB and the solvents below 100 °C. Above 100 °C, PHB was dissolved in all candidate solvents and kinetic factors became significant in determining the extent of PHB dissolution during fixed-time experiments, with N, N -dimethylcyclohexylamine dissolving as much as 25.86 g/L PHB in 25 h. These results show that the solubility parameter model is valid for switchable solvents and that these solvents exhibit a reversible interaction with PHB.