Key Points
- Material Development: Tokyo University of Science has created a glassy polymer with remarkable toughness of approximately 137 MJ/m³ and a Young’s modulus of around 0.9 GPa.
- Counterion Usage: The use of bulky DMAP counterions effectively suppresses nanoscale phase separation, addressing the brittleness commonly seen in ion-crosslinked glassy polymers.
- Potential Applications: These findings indicate potential for structural materials in transport equipment and electronics, where both rigidity and fracture resistance are essential.
Tokyo University of Science recently unveiled a groundbreaking glassy polymer that merges stiffness with toughness. By utilizing bulky organic ions, the researchers managed to mitigate nanoscale phase separation—a major cause of brittleness in hard plastics.
Research Breakthrough
On September 4, the research team reported achieving a material toughness of about 137 MJ/m³ and a Young’s modulus of 0.9 GPa in an ionic comb-shaped polymer. Notably, toughness was quadrupled post-neutralization, while elastic modulus and yield stress were about doubled, with findings published in Macromolecules on September 3.
Research Team
The study was conducted by Daisuke Aoki, Kotaro Uchiyama, Ryotaro Miyazawa, and Koji Arimitsu from the Faculty of Advanced Engineering and Department of Advanced Chemistry.
Problem Addressing
Glassy polymers typically maintain shape well due to their high modulus but suffer from brittleness. While ion-based physical crosslinking can enhance toughness in elastomers and hydrogels, glassy polymers often see ions clustering, which restricts chain motion and leads to embrittlement.
Methodology
The researchers compared various counterions by creating an ionic comb polymer with a polynorbornene backbone, densely populated with oligoethylene glycol side chains and carboxylic acids. Neutralization was achieved using either DMAP or sodium ions.
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DMAP Neutralization: Fourier-transform infrared spectroscopy confirmed ionization, while synchrotron small-angle X-ray scattering showed a consistent nanostructure. DMAP-enhanced samples demonstrated significant improvements in toughness and elasticity across various neutralization ratios.
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Sodium Neutralization: In contrast, sodium-neutralized samples faced phase separation. Although their elastic modulus surpassed 1.0 GPa, excessive neutralization caused a decline in elongation and increased brittleness.
Implications
This research introduces a new design guideline for toughening glassy polymers without relying on ionic liquids. The new material has promising applications in structural fields, especially in transport equipment and electronic devices where both rigidity and fracture resistance are crucial.
Conclusion
The success of DMAP, typically an esterification catalyst, underscores its dual role in synthesis and toughening of the polymer. Support for this innovative research was provided by the Japan Science and Technology Agency and the Japan Society for the Promotion of Science, among others.
