Initiated Chemical Vapor Deposition of Poly(1H,1H,2H,2H-perfluorodecyl Acrylate) Thin Films

Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 66-466, Cambridge, Massachusetts 02139, USA.
Langmuir (Impact Factor: 4.46). 12/2006; 22(24):10047-52. DOI: 10.1021/la061904m
Source: PubMed

ABSTRACT A solvent-free initiated chemical vapor deposition (iCVD) process was used to create low surface energy poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) thin films at deposition rates as high as 375 nm/min. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy showed full retention of the fluorine moieties, and no measurable cross-linking was detected. Additionally, the FTIR studies support the hypothesis that film deposition results from vinyl polymerization. For all iCVD PPFDA films, the static contact angle was found to be 120.8 +/- 1.2 degrees. The roughness of the films was found to be between 14.9 and 19.8 nm RMS, and the refractive index of the films was found to be between 1.36 and 1.37. The deposition rate was studied as a function of the substrate temperature and the partial pressure of the monomer. It was found that the deposition rate increases with decreasing substrate temperature and increasing monomer partial pressure. It was also found that the molecular weight increases with decreasing substrate temperature and increases with increasing monomer partial pressure. The highest molecular weight measured was 177 300 with a polydispersity of 2.27. Quartz crystal microbalance (QCM) measurements showed that these effects correlated with an increased monomer concentration at the surface. The deposition rate data and the QCM data were quantitatively analyzed to find the rate constants of the process using a previously published model for the iCVD process involving nonfluorinated monomers. The determined values of the rate constants of the surface polymerization were found to be similar to the rate constants measured in liquid-phase free radical polymerization. The kinetic data found in this paper can now be used to study iCVD deposition onto substrates with more complex geometries.

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    • "In particular, perfluoroacrylates offer fast polymerization due to the unsaturated acrylate group and hydrophobicity for the fluorinated pendant chain. As a result of the –CF 3 terminated side groups and comblike structure, the typical range of surface energies for fluorinated acrylic polymers is very low (5.6 to 7.8 mN/m) (Gupta & Gleason, 2006). "
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