Scientists at the Technion-Israel Institute of Technology have shown that polymer nanofibres become much stronger when their diameters are below a certain size.
Their research, published in the January issue of Nature Nanotechnology, could make possible stronger fabrics that use less material. Professor Eyal Zussman and Dr. Oleg Gendelman of the Faculty of Mechanical Engineering have proposed an explanation for this surprising behaviour in very thin fibres.
When the researchers measured the mechanical properties of nylon nanofibres, they found the critical diameter – the diameter at which the nylon nanofibre abruptly becomes stiffer – to be approximately 500 nanometers. They explained the abrupt increase in stiffness by considering the molecular structure inside the polymer fibre.
According to Zussman, the polymer macromolecules try to align themselves when the fibre is forming, but their length makes it impossible for them to align uniformly throughout the entire nanofibre. As a result, the nanofibre is a patchwork of differently oriented macromolecule regions. The researchers calculated the size of these regions to be roughly the same as the critical diameter of the nanofibre (the diameter at which the fibre stiffness abruptly increases).
“When the diameter of the fibre is much larger than the size of the oriented regions, the macromolecules can move relative to one another,” says Zussman. “But as the diameter of the fibre shrinks, these oriented regions become constrained and the macromolecules are unable to easily move relative to one another, and the resulting nanofibre is much stiffer.”
Although Professor Zussman and his colleagues focused on a certain type of nanofibre, they say their basic physical idea will help scientists understand the novel physical properties of a wide range of nanofibres and other nanostructures. Practical applications include lighter protective vests and stronger fabrics.
Also participating in the research, which is part of activities of the Russell Berrie Nanotechnology Institute at the Technion, were Dr. Arkadii Arinstein and graduate student Michael Burman.
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