Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Unusual Rods

Abstract:
Get thicker when stretched, thinner when compressed: simulations identify auxetic molecules

Unusual Rods

Posted on August 24, 2006

Day-to-day experience teaches us that stretching an object makes it thinner; pushing it together makes it thicker. However, there are also materials that behave contrary to our expectations: they get thicker when stretched and thinner when compressed. Known as “auxetic” substances, these materials include some foams and special crystals. Researchers at the Bar-Ilan University and the Israel Institute of Technology have now used quantum mechanical calculations to identify the first class of chemical compounds that behave auxetically on a molecular level.

When a usual material is, for example, hit by a ball, the material “flows” outward from the impact zone making the point of impact weaker. However, in auxetic materials, the matter “flows” inward, thus strengthening this zone. Such materials would be advantageous for bulletproof vests. Auxetic materials also provide interesting possibilities for medical technology. The introduction of implants such as stents to hold open blood vessels would be easier if, under pressure, the device would get thinner instead of thicker in the perpendicular direction.

In the auxetic materials known to date, the unusual behavior is a macroscopic property that stems from a special arrangement of the particles within the material, such as a particular weblike structure. Nanoscale auxetic materials are so far unknown.

By using quantum mechanical calculations, a team led by Shmaryahu Hoz has now predicted that there also exist certain molecules that behave auxetically: a class of compounds known as polyprismanes. These are rod-shaped molecules built up of several three-, four-, five-, or six-membered rings of carbon atoms stacked on top of each other. The prismanes made of three- and four-membered carbon rings show roughly equal auxetic effects, regardless of the number of stacked rings. The ones made of five- and six-membered carbon rings demonstrate significantly higher auxetic effects. Of all of the variations for which calculations were carried out, the prismane made of four six-membered rings showed the strongest effect. The researchers have not yet been able to unambiguously explain why prismane molecules behave auxetically.

“Although prismanes were discovered over 30 years ago, very few representatives of this class of compounds have been synthesized so far,” says Hoz. “We hope that our insights will act as an incentive to produce and characterize more prismanes.”

####


Author: Shmaryahu Hoz, Bar-Ilan University, Ramat-Gan (Israel), www.biu.ac.il/CH/faculty/hoz/hozint.html

Title: Auxetics at the Molecular Level: A Negative Poisson's Ratio in Molecular Rods

Angewandte Chemie International Edition, 2006, 45, No. 36, doi: 10.1002/anie.200601764

Contact:
Editorial office:
angewandte@wiley-vch.de

or David Greenberg (US)
dgreenbe@wiley.com

or Julia Lampam (UK)
jlampam@wiley.co.uk

Copyright © Angewandte Chemie

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

Possible Futures

Device to control 'color' of electrons in graphene provides path to future electronics August 31st, 2016

Graphene key to growing 2-dimensional semiconductor with extraordinary properties August 30th, 2016

Nanocatalysis for organic chemistry: This research article by Dr. Qien Xu et al. is published in Current Organic Chemistry, Volume 20, Issue 19, 2016 August 30th, 2016

Continuous roll-process technology for transferring and packaging flexible LSI August 29th, 2016

Materials/Metamaterials

Device to control 'color' of electrons in graphene provides path to future electronics August 31st, 2016

Graphene key to growing 2-dimensional semiconductor with extraordinary properties August 30th, 2016

A promising route to the scalable production of highly crystalline graphene films August 26th, 2016

Graphene under pressure August 26th, 2016

Announcements

Device to control 'color' of electrons in graphene provides path to future electronics August 31st, 2016

Graphene key to growing 2-dimensional semiconductor with extraordinary properties August 30th, 2016

University of Akron researchers find thin layers of water can become ice-like at room temperature: Results could lead to an assortment of anti-friction solutions August 30th, 2016

Nanocatalysis for organic chemistry: This research article by Dr. Qien Xu et al. is published in Current Organic Chemistry, Volume 20, Issue 19, 2016 August 30th, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic