Rob R' Graham

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Incorporation of Dyes into Polyelectrolyte
Multilayer films

• Rob R. Graham
• Darren J. Anderson
• M. Cynthia Goh

Lash Miller Chemical LaboratoriesToronto, ON
2
Why are Polyelectrolytes important?

• Polyelectrolytes (PEs) are polymers which have
  net charge on their side chains.
• They have applications to chemical sensors1,
  light emitting thin films2, and nonlinear
  optics3, to name only a few.
• Producing multilayer films is relatively cheap
  and easy.

Polyanion PSS
Polycation PDDA
3
How do you make a multilayer film?
from Decher 4
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Incorporation of Dyes into Multilayers

• With 1M NaCl in solution, the polyelectrolytes
  are collapsed around the small ions.
• The dyes penetrate into the polyelectrolyte
  layer.
• Dyes like amaranth with higher charge are
  electrostatically held more strongly than dyes
  with less charge like crystal violet.

D symbolized dyes of various charge
5
The Experiment

• 5 dyes were tested to gain an overview of surface
  morphology.
• Glass was used as a substrate for the films to be
  imaged on and atomic force microscope
• Films containing no dyes were created as
  standards.
• Charges on dyes of 3-, 2-, 1 and 2 were used.
• Other charges were not readily accessible

96 well microtitre plate
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How does AFM work?

• (AFM) is a topographical imaging technique.
• A piezo electric current moves the tip back and
  forth on the surface and the deflection of the
  laser is recorded. This changing voltage is
  converted to a height pattern.
• A 3D image is produced by several horizontal
  scans.

AFM schematic
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Morphology of Control Films

• When no dye was added, a documented 5
  vermiculate pattern characteristic of PDDA/PSS PE
  multilayer films was observed.

2 mg/ml
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Polyelectrolyte Multilayer Film Surfaces
2 mg/ml
1 mg/ml
.5 mg/ml
.25 mg/ml

• Surface morphology of four concentrations of PEM
  films incorporating Amaranth dye (above).
• The domains become less and less defined, until
  the lowest concentration where the surface
  becomes very rough.

________ 2.5 µm
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Polyelectrolyte Multilayer Film Surfaces
2 mg/ml
1 mg/ml
.5 mg/ml
.25 mg/ml

• Polyelectrolyte films incorporating Erioglaucine
  dye (below).
• The vermiculate morphology shrinks with
  decreasing PE concentration.
• Domains resemble control film morphology.

_________ 2.5 µm
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Polyelectrolyte Multilayer Film Surfaces

• Polyelectrolyte films incorporating crystal
  violet dye (below).
• Domains are virtually non-existant at high
  concentration, small ones become defined for
  mid-range concentration, and disappear for low
  concentration.

2 mg/ml
1 mg/ml
.5 mg/ml
.25 mg/ml
_________ 2.5 µm
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In Depth Characterization of Erioglaucine Films

• Silica slides were prepared, and a Uv-Vis
  spectrum was obtained for each layer of a
  ten-bilayer film deposition containing
  Erioglaucine.
• Separate films were scratched with a razorblade
  and scanned on the AFM in order to characterize
  the film thickness and measure the film growth
  per layer.

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Film Thickness
A razorblade is used to scratch the PE film off
of the substrate. The above AFM image shows that
the film is 130 nm thick.
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Increase in Dye Absorption with Bilayers
Maximum absorption (633 nm) increases
exponentially for each bilayer containing
Erioglaucine dye.
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Film Thickness and Absorption
The increase in absorption at 633nm appears to be
a linear function of the height of the film.
The film thickness increases exponentially with
increasing bilayers.
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Summary and Future Work

• Dyes can easily be incorporated into PEM films to
  give them unique optical properties.
• The concentration of polymers in solution affects
  the size of domains in the film.
• Absorption of Erioglaucine dye and film thickness
  both increase exponentially with increasing
  layers, while absorption appears to be a linear
  function of film thickness. This makes sense
  according to Beers Law.
• A similar study of both amaranth and crystal
  violet dyes should be done to determine if these
  relationships are unique to Erioglaucine.
• An attempt to incorporate more than one dye into
  a single film to narrow the range of transmitted
  light should be made.

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References
1. Ram, M. K., Carrara, S., Paddeu, S., Nicolini,
C., Thin Solid Films 1997, 302, 89 2. Yoo, D.,
Lee, J., Rubner, M. F., Mat. Res. Soc. Symp.
Proc. Vol. 413 3. Laschewsky, A., Mayer, B.,
Wischerhoff, E., Arys, X., Bertrand, P.,
Delcorte, A., Jonas, A., Thin Solid Films 1996,
285, 334 4. Decher, G. Science 1997, 277 1232 5.
McAloney, R. A., Sinyor, M., Dudnik, V., Goh, M.
C., Langmuir 2001, 17, 6655
Acknowledgements
I would like to thank the entire Goh group for a
terrific summer. I would also like to gratefully
acknowledge NSERC for funding this project, and
AstraZeneca for making the poster session
possible.