Home > Press > Nanoblinds
Helical polymer with side groups that synchronously flip “on command”
October 25, 2005
Some molecules occur in two versions related to each other like mirror images; this property is called chirality. For example, helical polymers are chiral - they can be either left- or right-handed helices. The left and right versions differ in their optical properties, such as their optical activity (they twist the plane of polarized light in opposite directions). Molecules whose optical properties can be precisely controlled - and switched - are highly sought after, as they present interesting possibilities for new data storage devices, optical components, or liquid-crystal displays. American researchers have now developed a helical polymer with side groups that can be flipped back and forth synchronously, like Venetian blinds.
The research team headed by Bruce M. Novak from North Carolina State University and Prasad L. Polavarpu from Vanderbilt University produced a helical polymer from an achiral building block. The use of a chiral catalyst made it possible to link the monomers exclusively into helices twisted in the same direction. Raising the temperature or changing the solvent causes a sudden - and reversible - change in some of the polymer’s optical properties (optical activity and electronic circular dichroism); contrary to expectations, one other property (vibrational circular dichroism) remains unchanged. What is happening with this molecule? Does the direction of the helix change? The researchers have now been able to prove that isn’t the case. The backbone of the polymer remains the same. The only explanation for these initially contradictory seeming observations is the following: the polymer has side chains that stick out from the backbone at an angle, like little flat wings. All of these “wings” twist around the bond that attaches them to the backbone. In the end, they point in the opposite direction, relative to the helix, from where they started. This occurs synchronously, like a Venetian blind being flipped.
Why does raising the temperature or changing the solvent cause this flip? The two wing positions are not equivalent. Depending on the polarity of the solvent, one or the other form of the molecule is stabilized. A higher temperature stabilizes the less energetically favorable form of the molecule, a lower temperature stabilizes the more energetically favorable form.
“The coordinated, blind-like flipping of the many side groups as the result of an external stimulus,” says Novak, “ could also indicate a very interesting potential for the construction of molecular motors and nanomachines.”
Author: Bruce M. Novak, North Carolina State University Raleigh (USA),
Title: A Thermal and Solvocontrollable Cylindrical Nanoshutter Based on a Single Screw-Sense Helical Polyguanidine
Angewandte Chemie International Edition
, doi: 10.1002/anie.200501977
or David Greenberg (US)
or Julia Lampam (UK)
Copyright © Angewandte Chemie
If you have a comment, please Contact
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Conference speakers: International think tank needed to identify techno-social turning points December 6th, 2013
Bangalore INDIA NANO 2013 Inaugurated December 5th, 2013
3-D printing and custom manufacturing: from concept to classroom: Strategic investments from NSF help engineers revolutionize the manufacturing process December 5th, 2013
The promise of nanotechnology December 4th, 2013
Nanorobot for transporting drugs in the body: The first step has been taken towards developing a nanorobot that – in the long run – will enable the targeted transport of medications in the body December 2nd, 2013
All aboard the nanotrain network November 11th, 2013
German-Finnish research team succeeds in organizing programmed nanoparticles into highly complex nanostructures: New principle for the self-assembly of patterned nanoparticles published in NATURE may have important implications for nanotechnology and future technologies November 7th, 2013
A swarm on every desktop: Robotics experts learn from public: Swarm robotics researchers at Rice University gather data with online game September 9th, 2013
104 Patents: Three UCF Professors Lauded as Top Innovators December 11th, 2013
Secretary Vilsack Announces Partnership to Advance Commercial Potential of Cellulosic Nanomaterial from Wood December 11th, 2013
Industrial Nanotech, Inc. Reinvents the Roof Tile - Will Bring Next Generation Roofing Product to Market in Early 2014 December 11th, 2013
AXT Exhibiting at SPIE Micro and Nanomaterials Conference December 11th, 2013