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Increased layer interdiffusion in polyelectrolyte films upon annealing in water and aqueous salt solutions
Thomas Krebs1, Hazel L Tan, Gunther Andersson
1University of Leipzig, Wilhelm-Ostwald-Institute of Physical and Theoretical Chemistry, Linnestrasse 2, 04103, Leipzig, Germany. thomaskrebs@gmx.de
Physical Chemistry Chemical Physics : PCCP
|November 23, 2006
Summary
Annealing polyelectrolyte multilayers in water or salt solutions enhances layer interpenetration. Increased salt concentration has a greater effect than temperature, promoting film equilibration by reducing electrostatic attraction.
Area of Science:
- Materials Science
- Polymer Science
- Surface Chemistry
Background:
- As-deposited polyelectrolyte multilayers are non-equilibrium structures.
- Strong electrostatic attraction between polyions suppresses interdiffusion during adsorption.
- Equilibration requires reducing this electrostatic attraction.
Purpose of the Study:
- Investigate the influence of annealing conditions on polyelectrolyte multilayer interpenetration.
- Determine the effect of temperature and salt concentration on film equilibration.
- Evaluate polyelectrolyte diffusion coefficients under different annealing conditions.
Main Methods:
- Utilized Neutral Impact Collision Ion Scattering Spectroscopy (NICISS).
- Annealed multilayer films in water and 1 M NaCl solutions at 20°C and 70°C.
- Employed ruthenium labeling for contrast between adjacent polyelectrolyte layers (poly(4-vinylpyridinium)/poly(4-styrenesulfonate)).
Main Results:
- Both temperature and salt significantly increase polyelectrolyte layer interpenetration.
- Salt concentration demonstrated a stronger influence on interpenetration than temperature.
- Numerical simulations yielded polyelectrolyte diffusion coefficients for various annealing conditions.
Conclusions:
- Annealing in aqueous solutions, especially with salt, promotes equilibration in polyelectrolyte multilayers.
- Increased interpenetration is attributed to enhanced charge screening and counterion binding.
- Findings provide insights into controlling the structure and properties of multilayer films.
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