Asphaltenic aggregates are polydisperse oblate cylinders.

Area of Science:

• Materials Science
• Physical Chemistry
• Colloid Science

Background:

• Small-angle neutron scattering (SANS) is crucial for characterizing asphaltenic aggregates in solution.
• Previous studies often lacked detailed analysis of model fit quality and applicable Q ranges.
• Accurate form factor selection is vital for determining asphaltene properties like radius of gyration and molar mass.

Purpose of the Study:

• To evaluate various intra-particle structure factor models for asphaltene SANS data.
• To assess model fit quality and physical reasonableness using Guinier analysis and reduced chi-squared values.
• To identify the most appropriate model for describing asphaltenic aggregate morphology.

Main Methods:

• Application of multiple monodisperse and polydisperse intra-particle structure factor models to SANS spectra.
• Comparison of model fit parameters (I(0), R(G)) with Guinier analysis results.
• Development of an analytical function for polydisperse oblate cylinders with Schultz distribution for scattering analysis.

Main Results:

• Agreement between model fit parameters and Guinier analysis suggests physical validity of the chosen models.
• Reduced chi-squared values quantified the goodness-of-fit across the studied Q range.
• The polydisperse radius oblate cylinder model demonstrated the best approximation for asphaltenic aggregate shapes.

Conclusions:

• The polydisperse oblate cylinder model provides a superior description of asphaltenic aggregate morphology.
• This study enhances the reliability of SANS analysis for asphaltene characterization.
• Accurate structural models are essential for understanding asphaltene behavior in solutions.