Crystallization behavior of binary even-even n-alkane mixtures in microcapsules: effect of composition and confined...

Area of Science:

• Materials Science
• Physical Chemistry
• Crystallography

Background:

• Normal alkanes (n-alkanes) are fundamental organic compounds with diverse applications.
• Binary mixtures of n-alkanes often exhibit complex crystallization behaviors, including solid-solid phase separation.
• Understanding these behaviors is crucial for controlling material properties.

Purpose of the Study:

• To investigate the crystallization of binary even n-alkane mixtures (C18/C20) in bulk and microencapsulated states.
• To elucidate the influence of confinement on the solid-solid phase separation and crystal structure.
• To determine the role of intermolecular interactions in confined binary alkane systems.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis.
• Temperature-dependent X-ray diffraction (XRD) for structural characterization.
• Investigation of both bulk and microencapsulated n-alkane mixtures (n-C18H38/n-C20H42).

Main Results:

• Solid-solid phase separation in C18/C20 mixtures is significantly suppressed or eliminated upon microencapsulation.
• The orthorhombic-ordered phase dominates the low-temperature crystal structure in microcapsules.
• Confinement weakens layered structures and terminal interactions, favoring miscibility and suppressing phase separation.

Conclusions:

• The confined environment within microcapsules plays a critical role in altering crystallization behavior.
• Microencapsulation enhances the miscibility of binary n-alkane systems by suppressing solid-solid phase separation.
• Confinement is a key factor, alongside composition and chain length, in controlling alkane mixture crystallization.