Journal of Supercritical Fluids | 2019
Conformational transitions of poly(ethylene oxide) in supersonic jets of supercritical CO2
Abstract
Abstract The supersonic gas jets are proposed as a tool for researching conformational transitions of polymer chain molecules in untraditional (supercritical) fluids. The working fluid of the jet and the solvent for polymers in this case are supercritical fluids. This method is used for the microencapsulation of TiO2 nanoparticles in poly(ethylene oxide) (Mv\u202f=\u202f8,000,000). The suspension of TiO2 nanoparticles in the polymer solution in supercritical carbon dioxide is expanded into vacuum or background gas. The substrate of the jet resulting from rapid expansion was investigated by SEM. Along the axis of the jet, zones of coil-globule-coil transitions were found. The position and extent of these zones can be controlled by varying the conditions in the reactor (pressure, temperature, co-solvent concentration) and background gas pressure in the nozzle chamber.