Reactive Parylenes
Most parylenes are passivation thin films or coatings. This means they protect the device or part from environmental stresses such as water, chemical attack, or applied field. This is an important property however many applications have the need to bond other materials to parylene, bond parylene to parylene, or even immobilize catalysts or enzymes to the parylene surface. Some of the reactive parylenes are parylene A (one amine per repeat unit, Kisco product), parylene AM (one methylene amine group per repeat unit, Kisco product), and parylene X (a reactive hydrocarbon cross-linkable version, not commercially available). Parylene AM is more reactive than A since it is a stronger base. When adjacent to the phenyl ring the amine group, -NH2-, is in resonance stabilization and therefore become more acidic and a result less reactive as a base. However, parylene A is much easier to synthesize and hence it costs less.
Among all the parylenes, parylene X is especially unique since it is: 1) cross-linkable (thermally or with UV light); 2) can generate the Cu-acetylide or Ag-acetylide metalorganic intermediates; 3) can undergo 'Click chemistry'; 4) can be used as an adhesive, parylene-to-parylene bonding without any by-products during processing; 5) is amorphous (non-crystalline); and 6) is a hydrocarbon polymer.
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