Liquid crystal polymers for non-reconstructing fluorinated surfaces

In order to obtain stable and efficient hydrophobic and oleophobic surfaces using coatings with highly fluorinated polymers, mesogenic segments structuring the orientation of fluorinated chains are introduced in the design of starting monomers. A novel series of liquid crystalline acrylic polymers incorporating a side semifluorinated segment linked to the inner polymeric chain via a monophenyl group, to avoid any surface reorganization phenomenon, is described. The mesomorphic properties are studied by a combination of polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The influence of the molecular parameters (perfluorinated chain length, spacer length) is discussed. Thermal stability of all the compounds is investigated using thermogravimetric analysis (TGA), while surface properties of the polymers are examined by static and dynamic contact angle goniometry. All the synthesized materials exhibit low surface energies and, when the lateral fluorinated tails are supported by a mesogenic unit, notable weak advancing/receding contact angle hystereses were observed (6 degrees vs. 31 degrees for the non-mesogenic polymers). These results demonstrate that surface organization at a macromolecular level, induced by both the fluorinated tails and the mesogenic core, generates remarkable surface stability. This concept can be extrapolated to the building of stable bioactive surfaces.