Structural reorganization of cylindrical nanoparticles triggered by polylactide stereocomplexation

Area of Science:

• Polymer Science
• Materials Science
• Supramolecular Chemistry

Background:

• Stereocomplexation of polymers like poly(L-lactide) and poly(D-lactide) enhances material properties.
• Crystallization-driven self-assembly is a key method for creating ordered polymer structures.

Purpose of the Study:

• To prepare stereocomplex micelles from poly(L-lactide)-b-poly(acrylic acid) and poly(D-lactide)-b-poly(acrylic acid) diblock copolymers.
• To investigate the morphological transitions during the self-assembly process.
• To explore the potential of these self-assembled structures in controlled release applications.

Main Methods:

• Preparation of diblock copolymers: poly(L-lactide)-b-poly(acrylic acid) and poly(D-lactide)-b-poly(acrylic acid).
• Crystallization-driven self-assembly in aqueous solutions.
• Morphological analysis of self-assembled structures (micelles).
• Investigation of morphological transitions under different conditions (solvent mixtures, temperature).

Main Results:

• Stereocomplex micelles were successfully prepared via crystallization-driven self-assembly.
• An unexpected morphological transition from cylinders to dense crystalline spherical micelles was observed.
• Disassembly of cylinders into stereocomplexed spherical micelles occurred in THF/H2O mixtures or at 65 °C in water.
• Similar transitions were observed in a related poly(ethylene oxide)-b-poly(lactide) system, indicating broader applicability.

Conclusions:

• A novel mechanism for morphological reorganization in block copolymers driven by competitive crystallization and stereocomplexation was discovered.
• This self-induced morphological transition offers new opportunities for advanced controlled release and delivery systems.
• The findings demonstrate the potential for designing sophisticated nanostructures with tunable properties through precise control of polymer stereochemistry and self-assembly conditions.