Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New theory may shed light on dynamics of large-polymer liquids

24.08.2011
A new physics-based theory could give researchers a deeper understanding of the unusual, slow dynamics of liquids composed of large polymers.

This advance provides a better picture of how polymer molecules respond under fast-flow, high-stress processing conditions for plastics and other polymeric materials.

Kenneth S. Schweizer, the G. Ronald and Margaret H. Professor of materials science and engineering at the University of Illinois, and graduate student Daniel Sussman published their findings in the journal Physical Review Letters.

“This is the first microscopic theory of entangled polymer liquids at a fundamental force level which constructs the dynamic confinement potential that controls slow macromolecular motion,” said Schweizer, who also is a professor of chemistry and of chemical and biomolecular engineering and is affiliated with the Frederick Seitz Materials Research Laboratory at the U. of I. “Our breakthrough lays the foundation for an enormous amount of future work relevant to both the synthetic polymers of plastics engineering and the biopolymers relevant to cell biology and mechanics.”

Polymers are long, large molecules that are ubiquitous in biology, chemistry and materials, from the stiff filaments that give cells their structure to plastics. Linear polymers fall into two classes: rigid rods like uncooked spaghetti or flexible strands like al dente noodles.

When in a dense solution, linear polymers become entangled like spaghetti in a pot, intertwining and crowding each other. Each polymer is hemmed in by its neighbors, so that the liquid behaves like an elastic, viscous rubber. Given enough time, the liquid will eventually flow slowly as polymers crawl along like snakes, a movement called reptation. Researchers have long assumed that each polymer’s reptation is confined to a tube-shaped region of space, like a snake slithering through a pipe, but have had difficulty understanding how and why the polymers behave that way.

Schweizer and Sussman’s new theory, based on microscopic physics, explains the slow dynamics of rigid entangled polymers and quantitatively constructs the confining dynamic tube from the forces between molecules. The tube concept emerges as a consequence of the strong interactions of a polymer with its myriad of intertwining neighbors. The theory’s mathematical approach sheds greater light on entanglement and better explains experimental data.

“Our ability to take into account these crucial physical effects allows us to predict, not assume, the confining tube concept, identify its limitations, and predict how applied forces modify motion and elasticity,” Schweizer said.

Not only does the new theory predict tube confinement and reptative motion, it reveals important limitations. The researchers found that the “tubes” weaken as applied forces increase, to the point where the tube concept fails completely and the liquid loses its rubbery nature. This is particularly important in plastics processing, which exposes polymer liquids to high stress conditions.

Next, the researchers plan to continue to study how external stress or strain quantitatively determine the driven mechanical flow behavior of entangled polymer liquids. They also hope to develop a theory for how attractive forces can compete with entanglement forces to result in soft polymer gels.

The National Science Foundation supported this work.

Editor’s notes: To reach Kenneth Schweizer, call 217-333-6440;
email kschweiz@illinois.edu.
The paper, “Microscopic Theory of the Tube Confinement Potential for Liquids of Topologically Entangled Rigid Macromolecules,” is available online:

http://prl.aps.org/abstract/PRL/v107/i7/e078102

Liz Ahlberg | University of Illinois
Further information:
http://www.illinois.edu

More articles from Physics and Astronomy:

nachricht Heating quantum matter: A novel view on topology
22.08.2017 | Université libre de Bruxelles

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Molecular volume control

22.08.2017 | Life Sciences

When fish swim in the holodeck

22.08.2017 | Life Sciences

Biochemical 'fingerprints' reveal diabetes progression

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>