Temperature- and time-resolved X-ray scattering at thin organic films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Supramolecular Chemistry

Background:

• Fe(II)-polyelectrolyte-amphiphile complexes (Fe-PAC) are advanced materials with potential applications in nanotechnology.
• Understanding their phase behavior is crucial for controlling their properties and performance.
• Thin film structures, like multilayers, offer unique properties compared to bulk materials.

Purpose of the Study:

• To investigate the temperature-dependent phase transitions of Fe-PAC multilayers.
• To simultaneously measure X-ray reflectivity and in-plane diffraction for detailed structural analysis.
• To determine the activation energies associated with observed phase transitions.

Main Methods:

• Simultaneous energy-dispersive X-ray reflectivity and in-plane diffraction measurements.
• Temperature- and time-resolved experiments conducted at BESSY II synchrotron facility.
• Langmuir-Blodgett (LB) technique used for depositing Fe-PAC multilayers on silicon substrates.

Main Results:

• An irreversible transition from the LB phase to a liquid-crystalline (LC)-like phase at approximately 318 K.
• Reversible loss of in-plane diffraction signal at 318 K, indicating rotational disorder with an activation energy of ~1.3 eV.
• A second irreversible transition to another LC phase occurred at approximately 338 K, with a reversible transition range between 329 K and 338 K.

Conclusions:

• Fe-PAC multilayers exhibit complex phase transition behavior upon heating.
• The combination of X-ray reflectivity and diffraction provides a powerful tool for characterizing thin film dynamics.
• The identified phase transitions and their reversibility offer insights for designing functional Fe-PAC based materials.