Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed an elastomer that is both stiff and tough.
To develop a polymer that is both stiff and tough, the researchers looked to physical, rather than chemical bonds to link the polymer chains.
Fine Tuning Polymer Entanglements
These physical bonds, called entanglements, have been known in the field for almost as long as polymer science has existed, but they’ve been thought to only impact stiffness, not toughness.
But the SEAS research team found that with enough entanglements, a polymer could become tough without compromising stiffness. To create highly entangled polymers, the researchers used a concentrated monomer precursor solution with 10 times less water than other polymer recipes.
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By crowding all the monomers into this solution with less water and then polymerizing it, we forced them to be entangled, like tangled strings of yarn,” said Guogao Zhang, a postdoctoral fellow at SEAS and co-first author the paper. “
Just like with knitted fabrics, the polymers maintain their connection with one another by being physically intertwined.”
Keeping the Polymer Stable
With hundreds of these entanglements, just a handful of chemical crosslinks are required to keep the polymer stable.
As elastomers, these polymers have high toughness, strength, and fatigue resistance. When the polymers are submerged in water to become hydrogels, they have low friction, and high wear resistance. That high fatigued resistance and high wear resistance increases the durability and lifespan of the polymers.
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We hope that this new understanding of polymer structure will expand opportunities for applications and pave the way for more sustainable, long-lasting polymer materials with these exceptional mechanical properties,” Junsoo Kim, graduate student at SEAS.
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Our research shows that by using entanglements rather than crosslinks, we could decrease the consumption of some plastics by increasing the durability of the materials,” said Zhang.
Harvard’s Office of Technology Development has protected the intellectual property associated with this project and is exploring commercialization opportunities.
Source: Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS)