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 Epoxy compound gets a graphene bump
14.11.2018 | Rice University

nachricht Automated adhesive film placement and stringer integration for aircraft manufacture
14.11.2018 | Fraunhofer IFAM

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Epoxy compound gets a graphene bump

14.11.2018 | Materials Sciences

Microgel powder fights infection and helps wounds heal

14.11.2018 | Health and Medicine

How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration

14.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>