Determining pore size distribution in wet cellulose by measuring solute exclusion using a differential refractometer

Area of Science:

• Materials Science
• Physical Chemistry
• Polymer Science

Background:

• Characterizing pore structure in wet cellulosic materials is crucial for understanding their properties.
• Traditional methods may not accurately assess microporosity in hydrated hydrophilic polymers.

Purpose of the Study:

• To develop and validate a solute exclusion method for determining pore volume and micropore size distribution in wet cellulosic materials.
• To establish a robust analytical approach combining experimental measurements with statistical modeling.

Main Methods:

• Utilized glucose, cellobiose, and polyethylene glycol (PEG) as molecular probes of varying sizes (8-130 Å).
• Measured probe concentrations before and after interaction with cellulose using the DNS method (sugars) and differential refractometry (PEG).
• Applied statistical analysis, including the Levenberg-Marquardt algorithm, to fit data to an empirical logistic model.

Main Results:

• Successfully determined pore volume and micropore size distribution in wet cellulosic samples.
• Demonstrated the importance of replicate sampling and statistical analysis due to sample variability.
• Obtained a smooth, increasing function representing the pore size distribution.

Conclusions:

• The developed solute exclusion method provides accurate pore structure characterization for wet cellulosic materials.
• The methodology, integrating differential refractometry and statistical modeling, is applicable to other wet, hydrophilic polymers.
• Potential applications include analyzing membranes, chromatographic supports, and gel-type resins.