Probing the Nano-Assembly Leading to Periodic Gratings in Poly(p-dioxanone)

Area of Science:

• Polymer science
• Materials science
• Crystallography

Background:

• Poly(p-dioxanone) (PPDO) is a biodegradable polymer with potential applications in biomedical fields.
• Understanding the crystallization behavior of PPDO is crucial for tailoring its properties.
• Dendritic cactus-arm-like ring bands represent an unusual morphology in PPDO crystallization.

Purpose of the Study:

• To elucidate the complex three-dimensional crystal structure of PPDO dendritic cactus-arm-like ring bands.
• To investigate the role of poly(vinyl alcohol) (PVA) as a diluent and its interaction with PPDO.
• To analyze the periodic arrangement and orientation of crystalline structures within the PPDO bands.

Main Methods:

• Scanning electron microscopy (SEM) with 3D dissection.
• Synchrotron radiation microfocal small-angle X-ray scattering (SAXS).
• Synchrotron radiation microfocal wide-angle X-ray diffraction (WAXS).
• Iridescence tests.

Main Results:

• 3D microscopy revealed periodic architectures composed of alternately normal-oriented flat-on crystals (valley) and horizontal-oriented edge-on fibrils (ridge).
• Oblique angles between valley crystals and branches ranged from 25-45°, confirmed by WAXS azimuthal angles.
• A grating-like strut-rib assembly was identified within the PPDO ring bands.

Conclusions:

• The study successfully characterized the intricate 3D crystalline architecture of PPDO dendritic ring bands.
• The findings provide insights into the crystallization mechanism of PPDO in the presence of hydrogen-bonding PVA.
• The identified grating-like structure offers potential for novel material designs and applications.