Combining Polarization Analysis and Isothermal Crystallization Behavior Elucidated by Two-Dimensional Correlation...

Area of Science:

• Polymer Science
• Materials Science
• Spectroscopy

Background:

• Polyhydroxybutyrate hydroxyhexanoate (PHBHx) is a microbial biopolymer with potential to replace petrochemicals.
• Understanding PHBHx morphology (crystallinity, phase orientation) is key to controlling its properties for commercial applications.
• Raman spectroscopy offers a method to probe the crystalline phase and dynamic crystallization behavior of PHBHx.

Purpose of the Study:

• To investigate the Raman spectral changes during the isothermal crystallization of PHBHx.
• To elucidate the morphology of PHBHx single crystals and spherulites using polarized Raman spectroscopy.
• To explain the origin of ring patterns observed in polarized light microscope images of PHBHx spherulites.

Main Methods:

• Isothermal crystallization study monitoring changes in Raman spectra.
• Polarized Raman spectroscopy of PHBHx single crystals.
• Polarized Raman spectroscopy and 2D-COS analysis of PHBHx spherulites.

Main Results:

• A correlation field splitting in the CH stretching band was identified, linked to interactions within the PHBHx unit cell.
• Polarized Raman spectra of single crystals explained the presence of residual amorphous material.
• Polarized Raman studies confirmed twisting of crystal ribbons in spherulites, consistent with strain-induced twisting models.

Conclusions:

• Raman spectroscopy is effective for characterizing PHBHx morphology during crystallization.
• The study provides a model explaining spherulite ring patterns based on twisting crystal ribbons and strain.
• These findings advance the understanding of PHBHx properties for potential biomaterial applications.