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.