High Performance Polymers, 2nd Edition

2Poly(p-xylylene)s

The discovery of poly(p-xylylene)s (PPX)s is

attributed to Szwarc in around 1947 [1]. He found

that the pyrolysis of p-xylene produces the p-xylyl

radical which disproportionates into a more stable p-

quinodimethane diradical. The diradical is somehow

stable in the gas phase, but not in the liquid phase. An

insoluble polymer is formed with a softening point

at 175

◦

C. Superficially, Szwarc was interested in the

bond strength of aromatic hydrogens [2], however, he

wrote a review on the topic [3], although he probably

became more famous for living polymers.

The deposition process was then improved and

commercialized by Gorham at Union Carbide ...