May 24, 2022

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High-energy shape memory polymer could someday help robots flex their muscles — ScienceDaily

When stretched or deformed, condition memory polymers return to their authentic styles just after heat or light-weight is utilized. These resources demonstrate fantastic assure for tender robotics, wise biomedical products and deployable area constructions, but until now they haven’t been ready to shop sufficient electricity. Now, scientists reporting in ACS Central Science have designed a form memory polymer that retailers practically 6 occasions much more strength than previous versions.

Form memory polymers alternate between an initial, undeformed condition and a secondary, deformed condition. The deformed condition is developed by stretching the polymer and is held in put by molecular adjustments, these kinds of as dynamic bonding networks or strain-induced crystallization, that are reversed with warmth or mild. The polymer then returns to its primary condition through the release of saved entropic electricity. But it can be been challenging for experts to make these polymers carry out electrical power-intensive tasks. Zhenan Bao and colleagues desired to establish a new sort of condition memory polymer that stretches into a steady, really elongated condition, permitting it to launch substantial amounts of power when returning to its original state.

The scientists included 4-,4′-methylene bisphenylurea units into a poly(propylene glycol) polymer backbone. In the polymer’s original point out, polymer chains were being tangled and disordered. Stretching triggered the chains to align and variety hydrogen bonds in between urea groups, creating supermolecular constructions that stabilized the highly elongated condition. Heating brought on the bonds to break and the polymer to deal to its initial, disordered point out.

In assessments, the polymer could be stretched up to 5 situations its authentic duration and store up to 17.9 J/g strength — almost 6 instances additional power than former shape memory polymers. The group shown that the stretched product could use this vitality to raise objects 5,000 situations its own body weight on heating. They also created an artificial muscle by attaching the pre-stretched polymer to the higher and reduced arm of a wooden mannequin. When heated, the materials contracted, leading to the mannequin to bend its arm at the elbow. In addition to its record-superior power density, the shape memory polymer is also economical (raw components price tag about $11 per lb) and uncomplicated to make, the researchers say.

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Materials presented by American Chemical Culture. Note: Material may be edited for fashion and length.