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 Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>