Light Scattering Study of a fluorinated Alkyl Methacrylate Polymer in Carbon Dioxide

The solution properties of fluorinated homopolymers in liquid and supercritical carbon dioxide were studied by light scattering. Poly(fluoroalkyl methacrylate) samples were fractionated by carbon dioxide (CO$_{2})$ to achieve narrow polydispersity and the refractive index of each sample in CO$_{2}$ was measured with a high pressure optical setup. Molecular weight, size, and interaction parameters of the polymer dissolved in CO$_{2}$ were studied as a function of temperature and CO$_{2}$ density using both static and dynamic light scattering. The solvent quality of CO$_{2}$ was shown to quantitatively improve with temperature and CO$_{2}$ density. We observed both $\theta $-temperature and $\theta $-density for poly(fluoroalkyl methacrylate) in CO$_{2}$. The hydrodynamic radius was found to increase with the temperature and density of CO$_{2}$. We demonstrate that the second virial coefficient of the polymer in CO$_{2}$ can be expressed in terms of the universal interaction parameter in the good solvent regime. This confirms that polymers in CO$_{2}$ have the same universal behavior as in organic solvents.