Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sandwich in a Pumpkin

21.02.2013
Supramolecular velcro for underwater adhesion

When gluing things together, both surfaces usually need to be dry. Gluing wet surfaces or surfaces under water is a challenge. In the journal Angewandte Chemie, Korean scientists have now introduced a completely new concept. They were able to achieve reversible underwater adhesion by using supramolecular "velcro".

Previously, researchers have primarily attempted to mimic natural underwater "adhesives" like the adhesive molecules used by mussels. Such substances adhere well in wet surroundings, but the adhesion is not reversible. A team led by Kimoon Kim at Pohang University of Science and Technology in Korea has chosen a different approach: they have moved away from natural models—and achieved reversible underwater adhesion.

The primary challenge for conventional adhesion under water is that the water molecules between the surfaces to be glued and the adhesive need to be removed so that these surfaces can react chemically. This is not the case with the new approach. Kim and his co-workers use host–guest interactions between water-soluble host molecule with a hydrophobic pocket and ionic guest molecule with a hydrophobic block. They form robust noncovalent bonds in water. In fact, the repulsion of water molecules is the driving force for formation of the bond, mediated by ion–dipole and hydrophobic interactions.

The researchers chose curcurbit[7]uril as their host and aminomethylferrocene as the guest. Cucurbit[n]uril (n = 5,6,7,8 and 10) are macrocycles—large, ring-shaped molecules made of multiple glycoluril units that can bind other molecules within their cavities. Their name is derived from cucurbita, the Latin name for pumpkin, which they resemble in shape. Ferrocenes are also known as sandwich compounds. The "bread" consists of two aromatic rings of five carbon atoms, while the "filling" is a single iron atom held in the middle. The ferrocene chosen by the researchers lodges very securely and specifically inside a "pumpkin" made of seven glycoluril units.

The researchers produced some silicon strips with many "pumpkins" attached, as well as some with many "sandwiches". When these strips come into contact with each other they stick together tightly, similar to Velcro. Once stuck together, a 1 x 1 cm piece of this supramolecular velcro can hold a weight of 2 kg in water. After drying in air it can hold as much as 4 kg. This is more than double-sided sticky tape can hold.

Like a macroscopic Velcro strip, the molecular version can be separated with a strong pull and reused multiple times. The adhesion can also be reversed chemically through application of a hypochlorite solution, which oxidizes the iron atoms. After reduction with an agent such as ascorbic acid, the velcro can adhere again.

Because the materials used are biocompatible, biological applications may be possible, for example in surgery suture or repairing live tissue. In comparison, the mussel mimetic underwater adhesives require strong oxidizing agents for curing to these applications, which is not the case with the new system.

About the Author
Professor Kimoon Kim is Director of the Center for Self-assembly and Complexity, under Institute for Basic Science (IBS), a newly created research initiative to make the Republic of Korea strong in fundamental research as well as developing new technologies. He also holds a Distinguished University Professorship position at the Department of Chemistry, Pohang University of Science and Technology (POSTECH). He is well-known for his research activities in supramolecular chemistry, especially in host–guest chemistry with cucurbiturils, as well as for introducing chiral metal–organic frameworks (MOF) and their use in heterogeneous asymmetric catalysis. Kim is a recipient of several awards including the Izatt–Christensen award in 2012.

Author: Kimoon Kim, Pohang University of Science and Technology (Republic of Korea), http://css.postech.ac.kr/

Title: Supramolecular Velcro for Reversible Underwater Adhesion

Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201209382

Kimoon Kim | Angewandte Chemie
Further information:
http://pressroom.angewandte.org

More articles from Life Sciences:

nachricht A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

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

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>