Correlations of surface free energy and solubility parameters for solid substances

Area of Science:

• Materials Science
• Physical Chemistry
• Polymer Science

Background:

• Surface free energy (γ) and solubility (δ) parameters are linked to cohesive energies and intermolecular forces.
• Understanding γ-δ correlations is crucial for fundamental science and practical applications.
• Existing empirical equations for γ-δ relationships are limited for solids due to the difficulty in obtaining molar volume (V~).

Purpose of the Study:

• To develop new empirical equations for surface free energy (γ) and solubility (δ) parameters that do not require molar volume (V~).
• To establish V~-free γ-δ correlations applicable to solid materials, including polymers and layered substances.
• To assess the applicability of these new equations to liquids.

Main Methods:

• Systematic exploration of γ-δ relationships using data from 21 solids (polymers, layered materials).
• Employed a trial-and-error fitting method to derive new equations.
• Tested the proposed equations on liquid data (nonpolar and polar).

Main Results:

• Six novel γ-δ equations, independent of molar volume (V~), were successfully proposed.
• The equations incorporate various surface free energy components (total γ_t, dispersive γ_d, polar γ_p) and solubility parameters (Hildebrand δ_t, Hansen δ_d, δ_p, δ_h).
• The V~-free equations demonstrated validity for most liquids, indicating broad applicability.

Conclusions:

• The developed V~-free γ-δ equations offer a method to estimate non-measurable parameters from measurable ones for solids.
• These findings are beneficial for solid material characterization and engineering applications.
• The equations' applicability to both solids and liquids broadens their utility in materials science.