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An international team, co-led by Ikerbasque Research Professor Alejandro J. Müller (POLYMAT–University of the Basque Country, EHU) and Professor Nikos Hadjichristidis (KAUST, Saudi Arabia), has shown that a polymer composed of five distinct, potentially crystallizable blocks is capable of self-organizing into an unprecedented internal structure. In the study, published in Nature Communications, Eider Matxinandiarena, the first author of the article, and Ricardo A. Pérez-Camargo, both researchers at POLYMAT-EHU, played a key role.

The material investigated is a pentablock polymer, consisting of five blocks: polyethylene (PE), poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), poly(L-lactide) (PLLA), and polyglycolide (PGA). All of them are biocompatible, and three (PCL, PLLA, PGA) are biodegradable. By integrating these five blocks within a single spherulite, it is possible to achieve multiple functions in a controlled manner. Its potential applications include the creation of new materials for:

Regenerative medicine: Designing tissue engineering scaffolds that degrade in stages, first providing mechanical support and then softer phases that promote regeneration.

Controlled drug release: Creating systems in which each block acts as a compartment with a different decomposition rate, allowing drugs to be released at specific times.

Advanced technologies: Developing materials with tunable mechanical, thermal, or optical properties through hierarchical control of their structure.

The work has been published in one of the most prestigious scientific journals in the world, thanks to its rigor and the precision with which crystal formation could be measured. Advanced characterization techniques available at the EHU laboratories, the ALBA synchrotron, and the University of Zaragoza were employed, as the crystals that form are approximately one million times smaller than a snowflake.

In this way, the team determined that crystallization occurs sequentially and hierarchically: PGA → PLLA → PE → PCL → PEO. Each block crystallizes on the structure generated by the previous one, building the material layer by layer. This hierarchical control allows modulation not only of which part crystallizes, but also how, when, and where—a key strategy for designing materials with advanced functional properties.

The spherulites exhibit the characteristic optical pattern of a positive Maltese cross, indicating that the polymer chains are oriented from the center outward, like the spokes of a wheel. This radial organization ensures that all phases maintain continuity with one another, despite being chemically different.

A Strategic International Collaboration

This work is part of several international scientific collaborations, including the European project POCTEFA AcroBioPlast, which focuses on new biopolymers for biomedical applications (poctefa-acrobioplast.com).

Reference

Matxinandiarena, E.; Pérez-Camargo, R. A.; Sebastián, V.; Zhang, P.; Ladelta, V.; Hadjichristidis, N.; Müller, A. J. (2025). Can five chemically different lamellar crystals self-assemble in a single spherulite? Nature Communications, 16, 9873. https://doi.org/10.1038/s41467-025-64845-6