Design chemistry for the environment: From processing fluoropolymers in supercritical carbon dioxide to new nonbiopersistent fluorinated coating materials.

摘要

The solution properties of a fluorinated alkyl methacrylate, poly(1,1,2,2-tetrahydro perfluorooctyl methacrylate) (PFOMA) in carbon dioxide (CO2) were studied by static and dynamic light scattering. The solvent quality of CO 2 was found to improve with increasing temperature and CO2 density as exhibited by an increase of the second virial coefficient. Both the hydrodynamic radius expansion factor and the second virial coefficient of PFOMA solution were found to be functions of a single interaction parameter that can be independently changed by either temperature or density variations. Furthermore, we demonstrate that the relationship between two directly measurable quantities, the second virial coefficient and the hydrodynamic expansion ratio, is the same for both temperature-induced and CO2 density-induced variations of solvent quality.; The degradation of coating materials that contain long perfluoro chains leads to the release of biopersistent perfluorooctanoic acid (PFOA) into the environment. In order to find environmentally friendly substitutes, a series of fluorinated alkyl methacrylate polymers containing the shorter and non-biopersistant perfluorobutyl group as the fluorinated component of the side chains are synthesized starting from perfuorobutyl iodide. Thermal properties of the polymers were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Static and dynamic contact angle measurements were used to quantify the surface properties of the thin films for these new non-biopersistant materials (C4 materials). The surface construction, especial the orientation of the fluorinated side chains, were recorded by near edge X-ray fine absorption structure (NEXAFS) experiments. In all, C4 materials displayed the hydrophobic and oleophobic properties with low surfaces tensions and their wetting properties were tuned by varying the "spacer" structures between the backbones and the perfluorinated groups of the side chains.