Polysulfobetaines in Aqueous Solution and in Thin Film Geometry

Area of Science:

• Polymer Science
• Solution Chemistry
• Materials Science

Background:

• Polysulfobetaines exhibit upper critical solution temperature (UCST) behavior in aqueous solutions.
• Poly(N,N-dimethyl-N-(3-methacrylamidopropyl) ammonio propane sulfonate) (PSPP) is a representative polysulfobetaine.

Purpose of the Study:

• Investigate the aqueous solution dynamics of PSPP above its cloud point.
• Examine the swelling behavior of PSPP thin films in water vapor.

Main Methods:

• Dynamic light scattering (DLS) to measure intensity autocorrelation functions.
• Turbidimetry to measure cloud points.
• Analysis of thin film swelling in water vapor.

Main Results:

• PSPP solution dynamics and spinodal temperatures are dependent on NaBr concentration, showing a maximum at low salt concentrations.
• Critical exponents for susceptibility and correlation length deviate from mean-field predictions.
• PSPP thin film swelling is dependent on film thickness, with optimal hydration observed around 100 nm.

Conclusions:

• NaBr concentration plays a crucial role in tuning the phase behavior and dynamics of PSPP solutions.
• The observed critical exponents suggest deviations from standard mean-field theory for PSPP solutions.
• Optimized film thickness is critical for efficient hydration of PSPP thin films.