Thermal Strain and Microstrain in a Polymorphic Schiff Base: Routes to Thermosalience

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• N-salicylideneaniline is a Schiff base derivative known for its thermosalient properties.
• Thermosalient materials undergo a phase transition upon heating, often with significant mechanical effects.

Purpose of the Study:

• To comprehensively investigate the structural and thermomechanical behavior of N-salicylideneaniline.
• To elucidate the distinct mechanisms behind its thermosalient phase transitions in different polymorphic forms.

Main Methods:

• Variable-temperature X-ray powder diffraction (VT-XRPD)
• Differential scanning calorimetry (DSC)
• Hot-stage microscopy
• Hirshfeld surface analysis

Main Results:

• Two distinct thermosalient mechanisms were identified in different polymorphic forms.
• Form I exhibits anisotropic thermal expansion leading to an explosive transition to Form IV.
• Form III shows a gradual transition via microstrain accumulation.

Conclusions:

• Hirshfeld surface analysis supports the dual-mechanism model of thermosalience.
• Integrating macro- and microscale descriptors is crucial for understanding responsive molecular solids.
• Findings inform the design of functional materials for actuation and sensing.