Influence of molecular weight dispersity of poly{2-(perfluorooctyl)ethyl acrylate} brushes on their molecular aggregation states and wetting behavior

Hiroki Yamaguchi, Moriya Kikuchi, Motoyasu Kobayashi, Hiroki Ogawa, Hiroyasu Masunaga, Osami Sakata, Atsushi Takahara

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Abstract

The relationships between the molecular aggregation states and water repellency of the perfluoroalkyl (R f) groups of poly{2- (perfluorooctyl)ethyl acrylate} (poly(FA-C 8)) brush thin films with broad and narrow molecular weight dispersities (MWDs) were analyzed by grazing incidence wide-angle X-ray diffraction (GI-WAXD) and water contact angle measurements. MWD-controlled-poly(FA-C 8) brush thin films were prepared by surface-initiated atom transfer radical polymerization on a flat silicon substrate in the absence and presence of an ionic liquid. In-plane diffraction profiles of poly(FA-C 8) brush films with narrow MWD had peaks corresponding to the periodic lengths of bilayer lamellae at q xy = 2-6 nm -1. This indicated that the orientation of R f groups were parallel to the surface of the silicon substrate. In contrast, the peak of the in-plane GI-WAXD for brush films with broad MWD brush was confirmed at q xy = 12.5 nm -1, indicating that the R f groups were oriented perpendicular to the surface of the silicon substrate. In the case of a poly(FA-C 8) brush thin film with a narrow MWD, the receding contact angle (θ R) and sliding contact angle (θ S) versus water were ca. 80° and 35°, respectively, whereas θ R and θ S were 105° and 15°, respectively, at the surface of poly(FA-C 8) with broad MWD. These results indicated that the water repellency of poly(FA-C 8) brush surface largely depends on the molecular aggregation state and orientation of the R f groups at the outermost surface and the MWD of the grafting polymer.

Original languageEnglish
Pages (from-to)1509-1516
Number of pages8
JournalMacromolecules
Volume45
Issue number3
DOIs
Publication statusPublished - Feb 14 2012

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All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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