Confocal Raman Microscopy for Measuring In-Situ Temperature-Dependent Structural Changes in Poly(Ethylene Oxide) Thin...

Area of Science:

• Materials Science
• Polymer Science
• Spectroscopy

Background:

• Crystallization from the melt is vital for semi-crystalline polymer properties.
• Structural analysis of thin polymer films during phase transitions is underexplored compared to bulk polymers.
• Understanding these transitions is key to controlling polymer material properties.

Purpose of the Study:

• To investigate temperature-dependent structural changes in poly(ethylene oxide) (PEO) thin films during melting and crystallization.
• To apply in situ Raman microscopy and self-modeling curve resolution (SMCR) analysis for detailed structural insights.
• To explore the potential of confocal Raman microscopy for analyzing ultra-thin polymer films.

Main Methods:

• In situ Raman microscopy was employed to monitor PEO films during thermal cycling.
• Self-modeling curve resolution (SMCR) analysis was used to resolve complex spectral data.
• Differential scanning calorimetry (DSC) was used for comparative thermal analysis.

Main Results:

• SMCR analysis identified two distinct structural phases in PEO films: ordered crystalline and disordered amorphous.
• Heating caused the crystalline structure to disappear, while cooling restored it from the amorphous phase.
• Raman band broadening above melting (67°C) and sharpening below crystallization (45°C) correlated with DSC measurements.

Conclusions:

• In situ Raman microscopy combined with SMCR analysis is a powerful tool for studying thin polymer film structural transitions.
• The methodology can analyze polymer films as thin as 2 µm, extending beyond conventional thermal analysis capabilities.
• This approach provides critical insights into the melting and crystallization behavior of surface-supported polymer films.