Kinks in experimental diffusion profiles of a dissolving semi-crystalline polymer explained by a...

Area of Science:

• Materials Science
• Polymer Science
• Physical Chemistry

Background:

• Polyethylene oxide (PEO) is a widely used polymer with applications in various fields.
• Understanding the dissolution behavior of PEO tablets is crucial for optimizing drug delivery and material processing.
• Phase transitions during polymer dissolution can significantly impact transport phenomena.

Purpose of the Study:

• To investigate the in situ dissolution process of semi-crystalline polyethylene oxide (PEO) tablets in water.
• To correlate the observed dissolution behavior with the melting transition of PEO.
• To elucidate the underlying diffusion mechanism governing PEO tablet dissolution.

Main Methods:

• In situ neutron radiography was employed to monitor the dissolution of PEO tablets in real-time.
• Neutron transmission images were analyzed to obtain polymer concentration profiles over time.
• The melting transition of the crystalline phase of PEO was identified as a key event during dissolution.

Main Results:

• Neutron radiography revealed a sharp diffusion front during PEO tablet dissolution.
• A pronounced kink in the polymer concentration profiles corresponded to the melting transition of PEO.
• Despite sharp fronts, the dissolution process was accurately described by Fickian diffusion models.

Conclusions:

• The dissolution of PEO tablets is characterized by a melting transition that influences the diffusion front.
• The observed phenomena, including sharp diffusion fronts, can be explained by Fickian diffusion with a concentration-dependent diffusion coefficient.
• This study provides insights into the complex interplay between phase transitions and mass transport in polymer dissolution.