The Two Faces of Janus Films

  • Author: Nancy McGuire
  • Published: 28 April 2016
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Source / Publisher: Langmuir/ACS Publications
  • Associated Societies: American Chemical Society (ACS), USA
thumbnail image: The Two Faces of Janus Films

Janus particles, which have two faces with differing properties, have been used as emulsifiers, as biomedical imaging agents, in electronic displays, and in other applications. Making self-supporting two-dimensional Janus films is difficult, however: the different functional groups tend to aggregate and form micelles.

Yara Ghoussoub and Joseph Schlenoff, Florida State University, Tallahassee, USA, produced Janus films by stacking 39 alternating layers of the hydrophilic components poly(diallyldimethylammonium), PDADMA, and poly(styrenesulfonate), PSS, on a solid substrate, with PDADMA layers on the top and bottom of the stack.

They coated the free surface with Nafion, a hydrophobic perfluorinated anionic polyelectrolyte, and they used a dilute alkaline solution to release the films from the substrate. Water contact angles were 94 degrees for the hydrophobic Nafion-coated surface and 34 degrees for the hydrophilic surface.

In addition to providing a hydrophobic surface, the Nafion coating protected the film's structure, preserving the layers for as long as 15 hours in a 2.5 M KBr solution. Films at least 400 nm thick were stiff enough to prevent self-association of the hydrophobic regions in salt solutions, but films thinned by treatment with salt solution folded spontaneously.


Article Views: 2129

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

If you would like to reuse any content, in print or online, from, please contact us first for permission. more

Follow on Facebook Follow on Twitter Follow on YouTube Follow on LinkedIn Follow on Instagram RSS Sign up for newsletters

Magazine of Chemistry Europe (16 European Chemical Societies) published by Wiley-VCH