In 2017, the scientific world buzzed with news that teams of chemists had synthesized an unusual material – ferroelectric nematic liquid crystals (FNs) – that flows like a liquid and has a polar order. Imagine a river of pencils with all the tips pointing in the same direction.
Now, a team of researchers including Worcester State physicist Maxim Lavrentovich has discovered that the molecule stacks in this new material spontaneously twist, giving it the unexpected quality of chirality – a geometric property where an object and its mirror image are intrinsically different or asymmetrical. Their findings were published March 22 in Science, a leading multidisciplinary peer-reviewed journal of the American Association for the Advancement of Sciences.
Maxim Lavrentovich, assistant professor in the Department of Earth, Environment, and Physics
Chirality is common in nature. When an object is chiral, it cannot be superimposed on its mirror image because the two images are not symmetrical. Human hands, golf clubs, scissors and shoes are all chiral. So too are most of the carbon-containing molecules in our body.
Until now, chiral materials were understood to have a predictable molecular structure – a carbon center that is bonded to four different groups of atoms. But FN’s don’t have that structure.
“It is a fundamental science discovery,” said Lavrentovich, an assistant professor in the Department of Earth, Environment, and Physics who specializes in theoretical soft condensed matter physics and biophysics. “It’s a new way in which you get chirality that does not depend on having chiral centers. It could also happen in nature, but we just haven’t looked for it yet.”
Lavrentovich’s co-authors, Priyanka Kumari, Bijaya Basnet and Oleg Lavrentovich, are from Kent State’s Advanced Materials and Liquid Crystal Institute. In their experiments with FNs, they observed the material in a thin flat film and discovered that the polar orientation twists randomly left and right, creating chirality. The polarity may be a key to understanding the behavior of FNs. “This work shows that polar orientational order of molecules could trigger chirality in soft matter with no chemically induced chiral centers,” the authors wrote.
As a theoretical biophysicist, Lavrentovich’s role in the research was the computational modeling of the FN’s twists and interpretation of their optical properties. He developed a model that predicts how light passes through the material, given certain twists.
The paper builds on a growing body of scientific research on ferroelectric nematic liquid crystals, which were first hypothesized more than 100 years ago by Nobel Prize winners Peter Debye and Max Born. FNs are a type of liquid crystal, which are commonly used in televisions, monitors and other electronics.
While the application of the team’s findings is not yet clear, there is excitement about what it suggests, said Lavrentovich. “It could be a mechanism that nature uses to create chirality that we didn’t appreciate before,” he said. “This is a discovery of a fascinating phenomenon. Building an actual theory for it is what I’m excited about as a physicist.”
Top photo: The image on the left is a microscopic view of how FN flows and the image on right depicts how the stacks of molecules twist. Image courtesy of Maxim Lavrentovich.
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