Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ideal nanocrystal produced from bulk plastics

28.08.2013
Polyethylene is an inexpensive commodity plastic found in many household objects.

Now, a consortium of researchers from Constance, Bayreuth, and Berlin has successfully used this plastic to synthesize the ideal polymer nanocrystal. The prerequisite was a new type of catalyst produced by Constance University researchers as well as a combination of unique analytic tools like those found at the Helmholtz Zentrum Berlin (HZB).


Polymer chain incorporation during formation of ideal PE-nanocrystals by catalytic insertion polymerization with a water-soluble Ni(II) catalyst. The amorphous layers covering both platelets act as the wheels of a pulley just changing the direction of the chains. A moderate raise of the temperature induces sufficient mobility that allows the chains to move within the crystal.

The crystalline nanostructure, which gives the polymer its new properties, could prove of interest to production of new kinds of coatings. The scientists’ findings are being published in the Journal of the American Chemical Society’s current issue (DOI: 10.1021/ja4052334).

Bringing materials with a disordered (amorphous) molecular structure into a crystalline form is a common endeavor pursued by chemists and material scientists alike. Often, it is only the crystalline structure which gives a material its desired properties. Therefore, basic science researchers have been interested in trying to identify physical principles that underlie the transition from a structure’s amorphous to its crystalline phase.

The most effective analytic tool that is needed for this is really a combination of various methods that are nowhere as concentrated as they are in Berlin. For the last three years, the HZB and Humboldt University Berlin have been running their Joint Lab for Structural Research. For Humboldt University, the lab was a key factor in their excellence initiative concept.

High polymer compounds like polyethylene, which exist as long molecular chains, are typically partly crystalline, meaning they consist of lamellar-like polyethylene crystals that are coated by a layer of amorphous polyethylene. These amorphous phases are characterized by a series of imperfections like knots. However, within an “ideal” nanocrystal, the amorphous regions act like deflection pulleys that change the direction of chains within the crystal by 180 degrees (see image).

Synthesis of such an ideal crystal has now been accomplished with the help of a new water-soluble catalyst, which allows for polymerization of ethylene in the aqueous phase. In the process, newly developing parts of the molecular chain are immediately incorporated into the growing crystal so that imperfections like entanglements are not allowed to form within the amorphous regions. The researchers gleaned these insights using X-ray diffraction methods and cryogenic transmission electron microscopy (TEM).

The nanocrystal suspension was produced by Prof. Stefan Mecking’s group at Constance University. For the cryo-TEM, HZB scientist Prof. Matthias Ballauff and his team produced a thin film of an aqueous polyethylene nanocrystal suspension and shock-froze it using cryogenically liquefied ethane. This resulted in formation of a glass-like solidified water modification, and the polyethylene nanocrystals enclosed within it can be analyzed using an electron microscope. The suspensions were also subjected to small-angle X-ray scattering (SAXS).

At a resolution of approximately one nanometer, the cryo TEM is the perfect tool for studying the tiniest structures within microemulsions and colloidal solutions. Along with X-ray diffraction experiments, this method has helped document the presence of perfect polymer nanocrystals. Says Matthias Ballauff: “This work shows that by combining microscopy and scattering, even complex systems can be analyzed with a degree of precision that is impossible using either method alone.”

Original article in Journal of the American Chemical Society

Dr. Ina Helms | Helmholtz-Zentrum
Further information:
http://www.helmholtz-berlin.de
http://www.helmholtz-berlin.de/pubbin/news_seite?nid=13779&sprache=en
http://pubs.acs.org/doi/full/10.1021/ja4052334

More articles from Materials Sciences:

nachricht Using a simple, scalable method, a material that can be used as a sensor is developed
15.02.2017 | University of the Basque Country

nachricht New mechanical metamaterials can block symmetry of motion, findings suggest
14.02.2017 | University of Texas at Austin

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>