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Summary
Investigating adsorbed water in dextran gel using near-infrared spectroscopy reveals water molecules exhibit slower reorientational jumps at lower hydration levels. Hydration mechanisms are highly cooperative across all relative humidities.
Area of Science:
- Physical Chemistry
- Materials Science
- Biophysics
Background:
- Understanding water's behavior in hydrogels is crucial for applications in drug delivery and tissue engineering.
- Dextran gels are widely used biomaterials, but the dynamics of adsorbed water within them remain incompletely understood.
Purpose of the Study:
- To investigate the state and dynamics of water adsorbed in dextran gel.
- To correlate thermodynamic properties with molecular dynamics of water in the gel.
Main Methods:
- Water-vapor adsorption-desorption isotherms were measured at three temperatures.
- Near-infrared (NIR) spectroscopy was employed to probe the adsorbed water.
- Fourier-inversion analysis of the H2O combination band (5184 cm⁻¹) was used to determine water microdynamics.
Main Results:
- Sorption heats were found to be dependent on both temperature and water coverage.
- Analysis of the NIR spectrum revealed water molecule reorientational jumps at picosecond timescales.
- Reorientational jumps were significantly slower (4-6 times) than free water at low to intermediate hydration, disappearing at saturation.
Conclusions:
- The hydration mechanism in dextran gel is highly cooperative across all relative humidities.
- Thermodynamic and microdynamical data suggest a strong interplay between water molecules and the dextran matrix.
- The findings provide insights into the structure and dynamics of water in polysaccharide-based hydrogels.