Temperature-Dependent Polymorphism and Phase Transformation of Friction Transferred PLLA Thin Films

Area of Science:

• Polymer Science
• Materials Science
• Crystallography

Background:

• Poly(L-lactic acid) (PLLA) is a biodegradable polymer with diverse applications.
• Controlling the crystalline structure of PLLA is crucial for tailoring its properties.
• Oriented polymer structures can exhibit enhanced mechanical and thermal characteristics.

Purpose of the Study:

• To investigate the effect of fast friction transfer technique on the crystalline structure of PLLA thin films.
• To explore the formation of different crystalline polymorphs (β, α', α) under varying friction transfer temperatures.
• To understand the phase transition behavior and solvent-induced transformations in oriented PLLA.

Main Methods:

• Synchrotron radiation wide-angle X-ray diffraction (WAXD) for structural analysis.
• Fourier transform infrared spectroscopy (FTIR) for chemical and structural characterization.
• In situ temperature-dependent WAXD and polarized optical microscopy (POM) for dynamic studies.

Main Results:

• Fast friction transfer successfully produced highly oriented PLLA films.
• Friction transfer temperature significantly influenced the formation of PLLA crystalline forms (β, α', α).
• Metastable β-form was readily generated, indicating the technique's suitability for its formation.
• Acetone treatment induced transformation to the stable α-crystalline form while preserving orientation.

Conclusions:

• The fast friction transfer technique offers precise control over PLLA crystalline structure and orientation.
• Temperature and solvent interactions play critical roles in PLLA polymorph control.
• The oriented PLLA films maintain structural integrity after solvent treatment, suggesting potential for advanced material applications.