Hydrolysis of Poly(fluoroacrylate) Thin Films Synthesized from the Vapor Phase

The post-synthesis surface reaction of vapor-deposited polymer thin films is a promising technique in engineering heterogeneous surface chemistry. Because the existing research has neglected marginally reactive precursor films in preference of their highly reactive counterparts, our knowledge of kinetics and loss of film integrity during the reaction are limited. To address these limitations, we characterize hydrolysis of two fluoroacrylates, poly(1H,1H,2H,2H-perfluorooctyl acrylate) (pPFOA) and poly(2,2,3,4,4,4-hexafluorobutyl acrylate) (pHFBA), with sodium hydroxide using X-ray photoelectron spectroscopy. Without crosslinking with di(ethylene glycol)divinyl ether (DEGDVE) and grafting with trichlorovinyl silane, the films degrade rapidly during hydrolysis. An S_N2 mechanism describes hydrolysis well, with rate constants of 0.0029 ± 0.0004 and 0.011 ± 0.001 L mol^-1s^-1 at 30 °C for p(PFOA-co-DEGDVE) and p(HFBA-co-DEGDVE), respectively. Our detailed study of hydrolysis kinetics of marginally reactive fluoroacrylates demonstrates the full capability and limitations of the post-synthesis reaction. Importantly, copolymers are characterized using a density correction new to polymer chemical vapor deposition.