Can five chemically different lamellar crystals self-assemble in a single spherulite?

Area of Science:

• Polymer Science and Engineering
• Materials Chemistry
• Crystallization Science

Background:

• Semicrystalline polymers with multiple crystallizable blocks offer advanced hierarchical structures and tunable properties.
• Understanding the crystallization behavior of complex multi-block polymers is crucial for material design but presents significant challenges.
• Biocompatible polymers are essential for advanced applications in medicine and beyond.

Purpose of the Study:

• To investigate the melt crystallization process of a novel pentablock quintopolymer.
• To determine the crystallization sequence of five distinct, biocompatible polymer blocks (PE, PEO, PCL, PLLA, PGA).
• To characterize the self-assembly and resulting morphology of the complex block copolymer.

Main Methods:

• Differential Scanning Calorimetry (DSC) for thermal analysis.
• Synchrotron in situ Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Scattering (WAXS/SAXS) for structural evolution.
• Transmission Electron Microscopy (TEM) and Polarized Light Optical Microscopy (PLOM) for morphological characterization.

Main Results:

• All five covalently linked blocks within the pentablock quintopolymer were found to crystallize upon cooling from a miscible melt.
• A distinct and reproducible crystallization sequence was identified: polyglycolide (PGA) > poly(L-lactide) (PLLA) > polyethylene (PE) > poly(ε-caprolactone) (PCL) > poly(ethylene oxide) (PEO).
• The crystallization process resulted in the formation of well-defined pentacrystalline positive spherulites, demonstrating a high level of self-assembly.

Conclusions:

• The study successfully demonstrates the sequential crystallization of all blocks in a complex pentablock quintopolymer.
• The observed hierarchical self-assembly into pentacrystalline spherulites highlights the potential for designing advanced multifunctional crystalline materials.
• This work provides fundamental insights into the crystallization behavior of multi-block copolymers, paving the way for novel material development.