Synchrotron small angle X-ray scattering study on the conformation of polystyrene in compressed CO2-toluene mixture

Synchrotron small angle X-ray scattering (SAXS) was performed to investigate the effect of dissolved CO₂ in toluene on the conformation of polystyrene (PS) in the solution. It has been found that the second virial coefficientA ₂ and the radius of gyrationR _g decrease with the increasing antisolvent CO₂ pressure. The scattering intensity of PS chain followedI(h) ∞h ^−α under different antisolvent pressures (0, 0.6, 1.5, 2.4, 3.3, and 4.2 MPa), suggesting that the PS chain has self-similar structure behavior or a fractal structure in the presence of antisolvent CO₂. All this reveals a large effect of antisolvent pressure or the solubility of CO₂ in the solution on PS structure. The fractal dimensions increase with the increasing antisolvent pressure, indicating that the polymer chain changes from a swollen coil into a rather dense globule in the course of adding antisolvent CO₂.