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 Graphene origami as a mechanically tunable plasmonic structure for infrared detection
25.04.2018 | University of Illinois College of Engineering

nachricht Scientists create innovative new 'green' concrete using graphene
24.04.2018 | University of Exeter

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Why we need erasable MRI scans

New technology could allow an MRI contrast agent to 'blink off,' helping doctors diagnose disease

Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is...

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

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

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Why we need erasable MRI scans

26.04.2018 | Medical Engineering

Balancing nuclear and renewable energy

26.04.2018 | Power and Electrical Engineering

Researchers 3-D print electronics and cells directly on skin

26.04.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>