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

Semicrystalline polymers with multiple crystallizable blocks provide opportunities to develop materials with hierarchical structures and customized properties, but they also pose unique challenges for understanding their crystallization. In this work, we investigate the crystallization from a miscible melt of a pentablock quintopolymer composed of five potentially crystallizable and biocompatible blocks, composed of polyethylene (PE), poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), poly(L-lactide) (PLLA), and polyglycolide (PGA), with a composition optimized to allow the crystallization of all blocks. Using Differential Scanning Calorimetry, synchrotron Fourier Transform Infrared Spectroscopy, synchrotron in situ Wide-angle and Small-angle X-Ray Scattering, Transmission Electron Microscopy, and Polarized Light Optical Microscopy, we demonstrate that upon cooling from the melt, all covalently linked blocks crystallize in a well-defined sequence: PGA > PLLA > PE > PCL > PEO. During crystallization, well-developed pentacrystalline positive spherulites are produced. This unprecedented level of self-assembly reveals the potential of complex block polymers to design multifunctional crystalline materials.