Morphology, molecular interactions and H₂O diffusion in a poly(lactic-acid)/graphene composite: A vibrational...

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Poly(l-lactic acid) (PLLA) is a biodegradable polymer with potential applications in various fields.
• Graphene nanoplatelets (GNP) are advanced nanofillers that can enhance polymer properties.
• Understanding the dispersion, interaction, and effect of GNP on PLLA matrix is crucial for developing advanced composite materials.

Purpose of the Study:

• To investigate the morphological properties, dispersion, and homogeneity of PLLA/GNP composites.
• To explore molecular interactions between PLLA and GNP using spectroscopic techniques.
• To evaluate the effect of GNP on water diffusion and uptake in PLLA.

Main Methods:

• Preparation of PLLA/GNP composites with 0.25 wt% and 0.75 wt% GNP content.
• Characterization using Raman spectroscopy, FTIR spectroscopy, and confocal Raman spectroscopy.
• First-principle calculations to support spectral interpretation.
• Time-resolved FTIR spectroscopy for investigating water diffusion.

Main Results:

• Achieved single-nanoplatelet dispersion at 0.25 wt% GNP; GNP aggregated into a co-continuous phase at 0.75 wt% GNP.
• Detected molecular interactions between PLLA and GNP, evidenced by perturbations in PLLA's conformational equilibrium.
• Observed significant decreases in both water diffusivity and equilibrium water uptake with increasing GNP content.

Conclusions:

• The preparation protocol influences GNP dispersion and homogeneity in PLLA composites.
• PLLA/GNP interactions affect the polymer's molecular structure and conformational equilibrium.
• GNP incorporation effectively reduces water absorption in PLLA, with implications for material stability and applications.