Measurement of oxygen diffusivity and permeability in polymers using fluorescence microscopy

Area of Science:

• Materials Science
• Polymer Chemistry
• Analytical Chemistry

Background:

• Luminescence oxygen sensors often exhibit non-linear Stern-Volmer (SV) responses due to luminophore heterogeneity within polymer matrices.
• This heterogeneity complicates accurate measurements of oxygen diffusion and permeation.

Purpose of the Study:

• To develop a fluorescence microscopy technique for investigating heterogeneities in luminescence oxygen sensors.
• To accurately measure oxygen diffusion and permeation coefficients in various polymer films.
• To overcome the limitations of the Stern-Volmer equation in heterogeneous sensor systems.

Main Methods:

• Utilized inverted fluorescence microscopy to analyze sensor responses at the micron scale.
• Investigated Stern-Volmer (SV) response linearity and quenching in different polymer regions.
• Developed a Fick's law based quasi-steady-state diffusion model combined with the SV equation.
• Employed film-on-sensor and accumulation-in-volume techniques for diffusion experiments.

Main Results:

• Identified that aggregated luminophore regions show higher intensity but poorer oxygen response.
• Demonstrated that homogeneous regions exhibit linear SV response with high SV constants.
• Successfully measured oxygen concentration using luminescence changes in linear response regions.
• Determined oxygen diffusion properties in Teflon, silicon elastomers, and polydimethylsiloxane films with zeolite.

Conclusions:

• The developed fluorescence microscopy technique effectively characterizes sensor heterogeneities and measures oxygen diffusion.
• The method provides precise determination of oxygen permeation coefficients in polymers.
• This approach enhances the reliability of luminescence-based oxygen sensing in heterogeneous materials.