Intermolecular Interactions in the Polymer Blends Under High-Pressure CO₂ Studied Using Two-Dimensional Correlation...

Area of Science:

• Polymer Science
• Materials Chemistry
• Spectroscopy

Background:

• High-pressure and supercritical carbon dioxide (CO2) are valuable in polymer processing.
• Understanding polymer-polymer interactions under these conditions is crucial for optimizing material properties.

Purpose of the Study:

• To investigate the mechanisms of polymer-polymer interaction in polycaprolactone-poly(lactic acid) (PCL-PLA) blends under high-pressure CO2.
• To visualize and differentiate intermolecular interactions within the blend using advanced spectroscopic techniques.

Main Methods:

• In situ attenuated total reflection Fourier transform spectroscopic imaging was employed.
• Two-dimensional correlation analysis and two-dimensional disrelation mapping were applied to analyze spectroscopic data.
• The study utilized a specially designed polymer interface to distinguish between different types of molecular interactions.

Main Results:

• Weak dipole-dipole intermolecular interactions were visualized for the first time using disrelation maps.
• Exposure to high-pressure CO2 weakened all three types of interactions: PCL-PCL, PLA-PLA, and PCL-PLA.
• An increased Flory interaction parameter was observed, directly correlating with phase separation in the PCL-PLA blend.

Conclusions:

• High-pressure CO2 significantly alters intermolecular forces in PCL-PLA blends, leading to reduced interactions.
• The observed increase in the Flory interaction parameter is the primary driver for phase separation under these conditions.
• The findings provide valuable insights for the effective processing of polymers using high-pressure and supercritical CO2.