Lee B. Steely

Hydrophobic and Superhydrophobic Polyphosphazenes

Polyphosphazenes are a class of hybrid organic–inorganic polymers that have good solubility in classical organic solvents and are thermo-oxidatively stable. Over the years, poly(dichlorophosphazene) has been used as a macromolecular intermediate to yield a number of polymers which can be hydrophobic or superhydrophobic. This review deals with several classical hydrophobic polyphosphazenes such as poly(bis-2,2,2-trifluoroethoxyphosphazene), species with siloxane containing substituents and phosphazene graft polymers. Poly(phosphazophosphazenes) and phenoxy-substituted polyphosphazenes are some of the more recent polymers that have been examined for their hydrophobic character. Processing methods such as electrospinning can enhance the hydrophobicity of polyphosphazenes to move them into the realm of superhydrophobic materials. Many polymers which are only borderline hydrophobic can now be converted into superhydrophobic materials by the use of environmental plasma treatment.

Plasma Surface Functionalization of Poly[bis(2,2,2-trifluoroethoxy)phosphazene]

Polyphosphazenes are a class of hybrid organic-inorganic macromolecules with high thermo-oxidative stability and good solubility in many solvents. Fluoroalkoxy phosphazene polymers also have high surface hydrophobicity. A method is described to tune this surface property while maintaining the advantageous bulk materials characteristics. The polyphosphazene single-substituent polymer, poly[bis(2,2,2-trifluoroethoxy)phosphazene], with flat film, fiber mat, or bead mat morphology was surface functionalized using an atmospheric plasma treatment with oxygen, nitrogen, methane, or tetrafluoromethane/hydrogen gases. Surface chemistry changes were detected by static water contact angle (WCA) measurements as well as X-ray photon spectroscopy (XPS). It was found that changes in the WCA of as much as 150 degrees occurred, accompanied by shifts in the ratio of elements on the polymer surface as detected by XPS. Overall this plasma technique provides a convenient method for the generation of specific surface characteristics while maintaining the hydrophobicity of the bulk material.