Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Scientists from the MSU studied new liquid-crystalline photochrom


Members of the Faculties of Chemistry and Fundamental Physical and Chemical Engineering at the Lomonosov Moscow State University in collaboration with foreign partners have synthesized and studied new liquid-crystal photochromic polymers.

Members of the Faculties of Chemistry and Fundamental Physical and Chemical Engineering at the Lomonosov Moscow State University in collaboration with foreign partners have synthesized and studied new liquid-crystal photochromic polymers.

This is an LCD texture observed in a polarization-optical microscope.

Credit: Alexey Bobrovsky

The Lomonosov Moscow State University scientists, cooperating with Czech colleagues from the Institute of Physics (Prague), have synthesized and studied new liquid-crystal polymers, combing optical properties of liquid crystals with mechanical properties of polymers.

Such polymers could quickly change molecular orientation under the influence of external fields and form coatings, films and details of complex shape. An important advantage of such systems in comparison with low-molecular-mass liquid crystals lies in the fact that at room temperature liquid-crystal polymers exist in the glass-like state, fixing molecular orientation.

Liquid-crystal polymers comprised of molecules with high molecular mass, called macromolecules. They are comb-shaped what implies that photosensitive rigid azobenzene fragments (C6H5N=NC6H5) are attached to the main flexible polymer chain with the help of spacers, consisting of CH2 moieties. These fragments are striving for sequencing and could form a wide variety of "packings" - namely, liquid-crystal phases. When light strikes such polymers, azobenzene groups isomerize, what results in alteration of polymers' optical properties. Such polymers are called photochromic.

The scientists have paid special attention to the processes of photoisomerization and photo-orientation. Photoisomerization is rearrangement of bonds inside a polymer molecule under the influence of light. Photo-orientation stands for alteration of rod-like azobenzene (in our case) fragments' orientation under the effect of plane polarized light, in whose direction of electric field is strictly determined. Being exposed to polarized light, azobenzene fragments change their angle in the course of photoisomerization cycles.

This occurs until their orientation becomes perpendicular to the polarization plane of the incident light and the fragments are no more capable of absorbing light. The photo-orientation process not only allows to change the orientation of azobenzene fragments of macromolecules but also causes emergence of dichroism and birefringence. Dichroism is difference of intensity of polarized light absorption in orthogonal directions. Birefringence refers to light beam splitting into two components with orthogonal (perpendicular) polarization; the direction of one of these components doesn't change, while the second beam is refracted.

Alexey Bobrovsky, RAS Professor, Doctor of Chemistry, Chief Research Fellow at the Department of High Molecular Compounds of the Faculty of Chemistry, Lomonosov Moscow State University, and one of the article authors says: "The key idea of our project is to study how the chemical structure of new comb-shaped liquid-crystal photochromic polymers influences their phase behavior and photooptical properties. Photoisomerization and photo-orientation processes allow exactly control phase behavior and optical properties of the elaborated systems."

At first, scientists from the Lomonosov Moscow State University in cooperation with their Czech colleagues from Institute of Physics, the Czech Academy of Sciences synthesized monomers, out of which the Lomonosov Moscow State University scientists obtained liquid-crystal polymers. The authors have studied phase behavior and temperatures of phase transitions of polymers, applying methods of polarizing optical microscopy and differential scanning calorimetry. X-ray structural analysis was used for studying detailed structure of phases at the Faculty of Fundamental Physical and Chemical Engineering of the Lomonosov Moscow State University.

According to the authors' words, the most significant project part was to study photooptical properties and photochromism of the obtained polymers. This stage was divided into two parts: irradiation of the polymer films by unpolarized UV light, during which photoisomerization (namely, rearrangement of intermolecular communications) took place. And the second part implied irradiation by polarized light resulted in photo-orientation.

Alexey Bobrovsky notices that the article relates to a major cycle of projects, devoted to photoinduced processes in photochromic liquid-crystal polymers. This article is research work only: the authors have studied interconnections between the chemical structure and the compound properties.

The scientist concludes: "Photoisomerization and photo-orientation open large perspectives for creation of so called "smart materials". They react to any external stimuli and could be used for information recording, storage and transfer, as well as in optical devices of diverse complexity. These precise polymers will be hardy used in a real-case scenario as they are too expensive and their synthesis is quite complicated. On the other hand, you can predict not in every instance, what systems will find application at what period of time and in what conditions."

Media Contact

Yana Khlyustova 

Yana Khlyustova | EurekAlert!

More articles from Materials Sciences:

nachricht Researchers demonstrate existence of new form of electronic matter
15.03.2018 | University of Illinois at Urbana-Champaign

nachricht Boron can form a purely honeycomb, graphene-like 2-D structure
15.03.2018 | Science China Press

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>