Nonsolvent-induced morphological changes and nanoporosity in poly(l-lactide) films

Area of Science:

• Materials Science
• Polymer Chemistry
• Crystallization Science

Background:

• Controlling polymer film morphology is crucial for material properties.
• Solvent-induced crystallization is a common method for polymer film formation.
• The influence of nonsolvents on poly(l-lactide) (PLLA) crystallization requires further investigation.

Purpose of the Study:

• To investigate the role of a nonsolvent in controlling PLLA film crystallization and morphology.
• To understand how different solvent/nonsolvent systems affect PLLA film structures.
• To explore the potential for tailoring polymer film morphologies using nonsolvents.

Main Methods:

• Poly(l-lactide) (PLLA) films were crystallized using various solvent/nonsolvent systems (e.g., THF/water, acetone/water).
• Microscopy techniques (e.g., SEM) were employed to analyze film morphology.
• Small- and wide-angle X-ray scattering (SAXS/WAXS) were used to study crystalline structures.

Main Results:

• PLLA films crystallized in pure THF or acetone exhibited large spherulites (40-80 μm).
• The addition of water as a nonsolvent resulted in nanosized voids and smooth film surfaces.
• Macroporous structures with larger voids and rough surfaces were observed in films crystallized with globular structures in pure solvents.

Conclusions:

• Nonsolvents significantly alter PLLA crystallization, leading to nanosized voids and smooth surfaces.
• Interface-enhanced crystal nucleation in solvent/nonsolvent systems drives void formation.
• This nonsolvent-mediated crystallization method can be extended to control morphologies of other polymer films.