Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tricolor Liquid Crystals

03.08.2011
Thermal and mechanical stimuli switch the luminescence of a liquid-crystal mixture between three different colors

Luminescent materials that change their light-emitting properties in response to external stimuli could provide interesting new approaches for novel storage materials, sensors, security materials, and information displays.

Typically, such materials can either be switched from “on” to “off” or between two different colors. It has not previously been possible to switch between three different stable colors with materials containing only a single luminescent substance. In the journal Angewandte Chemie, Takashi Kato and Yoshimitsu Sagara from the University of Tokyo (Japan) have now introduced a liquid-crystalline material that can be switched back and forth between three different colors by means of thermal and mechanical stimuli.

The new material consists of two dumbbell-shaped organic compounds—one small and one large, both consisting of a branched arrangement of aromatic six-membered rings. The large molecule contains an anthracene component as the luminescent group (luminophore). This mixture of molecules aggregates to form liquid crystals. Molecules in a liquid-crystalline state are partially ordered like in a crystal, but are mobile like in a liquid. Liquid crystals are most commonly found in liquid-crystal displays.

The Japanese researchers prepared thin films of their special liquid crystals. Under UV light, these films glow red-orange. Mechanical shearing, such as rubbing, at 90 °C changes the arrangement of the liquid crystals—the rubbed areas now appear green. This new, green phase is stable between room temperature and 146 °C. This amazing film can do more: both the red-orange and green phases can be changed to a yellow one by rubbing at room temperature. Heating to 145 °C and subsequent cooling to room temperature changes the green and yellow back to red-orange.

If this luminescent mixture can be incorporated into materials such as structural polymers, the thermal and stress histories for the materials are easily detected by bright luminescence color changes. Knowledge of these histories is useful for the maintenance of the materials systems, which include coatings and plastics. In addition, artists may be interested in these materials because of the beauty of the luminescence colors and the ease of writing/erasing and stability of the generated images.

Author: Takashi Kato, University of Tokyo (Japan), http://kato.t.u-tokyo.ac.jp/index-e.html
Title: Brightly Tricolored Mechanochromic Luminescence from a Single-Luminophore Liquid Crystal: Reversible Writing and Erasing of Images

Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201100914

Takashi Kato | Angewandte Chemie
Further information:
http://pressroom.angewandte.org
http://kato.t.u-tokyo.ac.jp/index-e.html

More articles from Life Sciences:

nachricht Closing in on advanced prostate cancer
13.12.2017 | Institute for Research in Biomedicine (IRB Barcelona)

nachricht Visualizing single molecules in whole cells with a new spin
13.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>