Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Needle and thread molecules connecting materials in new ways

27.03.2003


Determining details of attraction in mechanically-linked molecules allows chemists to fine-tune shapes, capabilities of supramolecules for improved and new polymers

Virginia Tech chemistry professor H.W. Gibson and his students have been able to take advantage of self assembly to create new chemical structures from mechanically-linked molecules. Gibson will give an invited talk in the Division of Polymer Chemistry at the 225th national meeting of the American Chemical Society March 23-27 in New Orleans.

The field of mechanically-linked chemistry uses a limited set of compounds as building blocks for supramolecules. Starting with crown ethers, which are rings (the ’hosts’), and rod-shaped molecules such as ammonium ions (the ’guests’), the chemists thread the rings with the rods to create molecules called pseudorotaxanes. Bulky groups are then added to the ends of the rods so they won’t unthread and these molecules are rotaxanes.



The attractive forces between the rings and rods is what allows them to self-assemble into pseudorotaxanes. "It’s an equilibrium process," says Gibson.

The researchers in Gibson’s lab studied these complexes using x-ray crystallography to understand the forces that hold the different compounds together. "The x-rays gave us the exact angles and distances, allowing us to determine the attractive forces," says Gibson.

Now the researchers are putting those molecular entities at the end of polymer chains, like spaghetti strands with selective host and guest species at the ends that will only complex with each other. "It’s like a needle and thread, but only a certain thread will pass through the eye of the needle," says Gibson. What also makes the new molecule interesting is that it is held together by a noncovalent bond, meaning it can be reversed.

"We are trying to create materials at low temperatures that have the properties of block copolymers," says Gibson. "If heated, they will loosen and come apart. Such materials are easier to process. Heat causes them to revert to smaller molecules, so the material has lower viscosity. It would take less pressure to force them into a mold and you could create very thin molds."

Compare that to a thermosetting polymer that must be heated to 200 degrees C to be processed. "If there is a problem, you have to throw it away because it is not soluble or meltable. The thread and needle material could simply be reprocessed because the molecules would separate at the noncovalent bond into the smaller units, then could be allowed to reform into the specific supramolecular thread and needle."

Joining chain polymers using pseudorotaxanes could also make it possible to tailor the materials joined in block copolymers to improve mechanical or other behavior. For instance, by selection of one of a series with host species at the chain ends (from column A) and one from a series of polymers with guest species at chain ends (from column B) a range of block copolymers could be assembled and tested very readily. These systems would be analogs of traditional covalent block copolymers such as impact resistant styrene-butadiene systems.

Gibson’s group has also connected up to 12 crown ethers to C60 fullerene (60 carbon atom buckeyball) and separately up to 12 guest species. These octopus-like 12-armed species can interact with the end-functionalized polymers described above to encapsulate the buckeyeball, thus isolating the fullerene core for various applications, such as catalysis and enhanced solubility.

Gibson will deliver the paper, " Self-assembly with molecular buildings blocks (Poly 611)," co-authored by Zhongzin Ge, Jason W. Jones, and Aurica Farcas, at 9:45 a.m., Wednesday, March 26 in the Hilton Riverside Grand Salon C18/C15.

Jones and Feihe Huang, Gibson’s Ph.D. students, will also deliver papers in the Organic Chemistry Division on related research results.
See separate news releases.


Contact for more information: Dr. Harry Gibson, hwgibson@vt.edu, 540-231-5902
PR CONTACT: Susan Trulove 540-231-5646 strulove@vt.edu

Harry Gibson | EurekAlert!
Further information:
http://www.technews.vt.edu/

More articles from Life Sciences:

nachricht Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory

nachricht How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>