Molecular mixing creates super stable glass

Date:
October 14, 2021
Source:
Chalmers University of Technology
Summary:
Researchers have succeeded in creating a new type of super-stable,
durable glass with potential applications ranging from medicines,
advanced digital screens, and solar cell technology. The study
shows how mixing multiple molecules -- up to eight at a time --
can result in a material that performs as well as the best currently
known glass formers.



FULL STORY ========================================================================== Researchers at Chalmers University of Technology, Sweden, have succeeded
in creating a new type of super-stable, durable glass with potential applications ranging from medicines, advanced digital screens, and solar
cell technology.

The study shows how mixing multiple molecules -- up to eight at a time
-- can result in a material that performs as well as the best currently
known glass formers.


==========================================================================
A glass, also known as an 'amorphous solid', is a material that
does not have a long-range ordered structure -- it does not form a
crystal. Crystalline materials on the other hand are those with a highly ordered and repeating pattern. The fact that a glass does not contain
crystals is what makes it useful.

The materials that we commonly call 'glass' in every day life are mostly silicon dioxide-based, but glass can be formed from many different
materials.

Researchers are therefore always interested in finding new ways to
encourage different materials to form this amorphous state, which can potentially lead to the development of new types of glass with improved properties and new applications. The new study, recently published in
the scientific journal Science Advances, represents an important step
forward in that search.

"Now, we have suddenly opened up the potential to create new and better
glassy materials, by simply mixing many different molecules. Those
working with organic molecules know that using mixtures of two or three different molecules can help to form a glass, but few might have expected
that the addition of more molecules, and this many, would achieve such
superior results," says Professor Christian Mu"ller at the Department
of Chemistry and Chemical Engineering at Chalmers University who led
the research team behind the study.

Best result for any glass forming material A glass is formed when a
liquid is cooled down without undergoing crystallisation, a process
called vitrification. The use of mixtures of two or three molecules to encourage glass formation is a well-established concept.

However, the impact of mixing a multitude of molecules on the ability
to form a glass has received little attention.



==========================================================================
The researchers experimented with a mixture of up to eight different
perylene molecules which, individually, have a high fragility -- a
property related to how easy it is for a material to form a glass. But
mixing the many molecules together resulted in a substantial decrease
in fragility, and a very strong glass former with ultralow fragility
was formed.

"The fragility of the glass we created in the study is very low,
representing the best glass-forming ability that has been measured not
only for any organic material but also polymers and inorganic materials
such as bulk metallic glasses. The results are even superior to the glass forming ability of ordinary window glass, one of the best glass formers
that we know of," says Sandra Hultmark, doctoral student at the Department
of Chemistry and Chemical Engineering and lead author of the study.

Extending product life and saving resources Important applications for
more stable organic glasses are display technologies such as OLED screens
and renewable energy technologies such as organic solar cells.

"OLEDs are constructed with glassy layers of light-emitting organic
molecules.

If these were more stable it may improve the durability of an OLED and ultimately the display," Sandra Hultmark explains.

Another application that may benefit from more stable glasses
are pharmaceuticals. Amorphous drugs dissolve more quickly, which
aids rapid uptake of the active ingredient upon ingestion. Hence,
many pharmaceuticals make use of glass-forming drug formations. For pharmaceuticals it is vital that the glassy material does not crystallise
over time. The more stable the glassy drug, the longer the shelf life
of the medicine.

"With more stable glasses or new glass forming materials, we could extend
the lifespan of a large number of products, offering savings in terms
of both resources and economy," says Christian Mu"ller.

More about the research
* The researchers chose to work with a series of small, conjugated
molecules comprising a perylene core with different pendant alkyl
groups at one of the bay positions. All eight perylene derivatives
readily crystallise when cast from solution and show a fragility
of more than 70.

* Mixing of eight perylene derivatives resulted in a material that
displays
a fragility of only 13, which is a record low value for any glass
forming material studied to date, including polymers and inorganic
materials such as bulk metallic glasses and silicon dioxide.

* The research project was funded by the Swedish Research Council, the
European Research Council, as well as the Knut and Alice Wallenberg
Foundation through project: Mastering Morphology for Solution-born
Electronics.

========================================================================== Story Source: Materials provided by
Chalmers_University_of_Technology. Original written by Jenny Holmstrand
and Johsua Worth. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sandra Hultmark, Alex Cravcenco, Khushbu Kushwaha, Suman Mallick,
Paul
Erhart, Karl Bo"rjesson, Christian Mu"ller. Vitrification of
octonary perylene mixtures with ultralow fragility. Science
Advances, 2021; 7 (29): eabi4659 DOI: 10.1126/sciadv.abi4659 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211014100128.htm

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