New material confirms old theories

Researchers at Cornell University have developed a new class of hybrid materials that could be used in a wide range of applications, including microelectronics.

Using nanoscale chemistry, researchers at Cornell University have developed a new class of hybrid materials that they describe as flexible ceramics. The new materials are touted to have wider applications, from microelectronics to separating macromolecules, such as proteins.

What is particularly striking, according to the researchers, is that under the transmission electron microscope (TEM) the molecular structure of the new material – known as a cubic bicontinuous structure – conforms to century-old mathematical predictions.

‘We in polymer research are now finding structures that mathematicians theorised long ago should exist,’ said Ulrich Wiesner, associate professor of materials science and engineering at Cornell. The structure of the new material appears so convoluted that it has been dubbed ‘the plumber’s nightmare.’

‘The material has properties that are not just the simple sum of polymers plus ceramic, but maybe something quite new,’ said Wiesner. So far the Cornell researchers have made only small pieces of the flexible ceramic, weighing a few grams, but that is enough to test the material’s properties.

The new material is said to be transparent and bendable but with considerable strength. Unlike pure ceramic the material will not shatter. In one form the hybrid material is an ion conductor with great promise as highly efficient battery electrolytes. There is also the possibility that the new material could be used in fuel cells, said Wiesner.

The porous structure of the flexible ceramic forms when the material is heat-treated at high temperatures. In fact, said Wiesner, this is the first material with such a symmetry and narrow pore-size distribution. Because the material has pores only 10 to 20 nanometers across, Wiesner is collaborating with Larry Walker, Cornell professor of biological and environmental engineering, to see if the material can be used to separate live proteins.

Wiesner believes that because of the material’s self-assembling ability, it could be produced in large batches. ‘We have perfect structure control,’ he said. ‘We can structure the material down to the nanoscale with unprecedented control. We now know how to make a suite of structures of assorted shapes and pore sizes.’

The Cornell researchers can do this by controlling the ‘phases,’ or molecular architectures, of the material by controlling the mix of the polymer and the ceramic.

The material goes through several shifts in shape, from cubic to hexagonal to lamellar – thin and platelike – to inverse hexagonal and inverse cubic. After the lamella phase and before the inverse hexagonal, the material forms the cubic bicontinuous structure – the ‘plumber’s nightmare’- that was not previously known to exist in polymer systems.

The ‘plumber’s nightmare’ may be only the first of these highly adaptable structures made possible by the specific combination of polymers and ceramics, said Wiesner. ‘There is a good chance that we will find a whole zoo of other bicontinuous structures that people didn’t know existed in polymers. We have opened the avenue to finding further such structures,’ he added.

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