c-Perpendicular Orientation of Poly(ʟ-lactide) Films

Area of Science:

• Polymer Science
• Materials Science
• Crystallography

Background:

• Poly(ʟ-lactide) (PLLA) is a biodegradable polymer with significant applications.
• Controlling the crystalline orientation in PLLA films is crucial for optimizing material properties.
• Previous methods have not achieved perpendicular chain alignment in PLLA films.

Purpose of the Study:

• To achieve unprecedented perpendicular chain axis orientation (c⊥ orientation) in Poly(ʟ-lactide) films.
• To investigate a novel method for inducing crystallization and orientation in PLLA.
• To characterize the crystalline phases and optical properties of the resulting films.

Main Methods:

• Inducing crystallization of amorphous PLLA films via low-temperature sorption of guest molecules (e.g., N,N-dimethylformamide, cyclopentanone, 1,3-dioxolane).
• Utilizing two-dimensional wide-angle X-ray diffraction (2D-WAXD) with EDGE patterns (X-ray beam parallel to film plane) to analyze chain orientation.
• Quantifying the c⊥ orientation by analyzing hk0 arcs on the meridian of the diffraction patterns.

Main Results:

• Successfully obtained PLLA films with co-crystalline and crystalline α phases.
• Achieved preferential perpendicular orientation (c⊥) of polymer chain axes relative to the film plane.
• The guest-induced crystallization method resulted in highly transparent PLLA α-form films, comparable to amorphous films.
• Demonstrated and quantified the c⊥ orientation using 2D-WAXD EDGE patterns.

Conclusions:

• Low-temperature guest-induced crystallization is an effective method for achieving unprecedented c⊥ orientation in PLLA films.
• This novel orientation technique yields highly transparent crystalline PLLA films.
• The findings open new possibilities for advanced PLLA-based materials with tailored optical and mechanical properties.