Relation between colour- and phase changes of a leuco dye-based thermochromic composite

Area of Science:

• Materials Science
• Physical Chemistry

Background:

• Reversible color change in leuco dye composites is typically linked to phase transitions.
• Similar thermal behavior is expected for both phenomena.

Purpose of the Study:

• Investigate the effect of spatial confinement on the relationship between color change and phase transition in leuco dye composites.
• Analyze how different confinement structures influence thermal hysteresis and crystallization behavior.

Main Methods:

• Differential Scanning Calorimetry (DSC) for phase transition analysis.
• UV-Vis spectroscopy for monitoring color change.
• Comparison of bulk, open-porous, and microencapsulated composite systems.

Main Results:

• Spatial confinement alters the correlation between color change and phase transition, particularly during cooling.
• Microencapsulation leads to two distinct crystallization processes, with the second occurring ~20°C lower than bulk.
• Coloration in microencapsulated systems precedes the second crystallization, widening hysteresis to 18°C.

Conclusions:

• The relationship between color change and phase transition is sensitive to spatial confinement.
• Microencapsulation introduces unique crystallization behaviors affecting thermal hysteresis.
• Design considerations for phase-change material applications must account for these confinement-induced effects.