Polymer brushes are polymers in which individual polymer chains stand side by side on a surface, causing the chains to stick out like bristles on a brush.
In the journal Angewandte Chemie, American scientists have now presented a new simple method for making three-dimensional nanostructures in a controlled fashion from polymer brushes.
There are a wide variety of current and future applications for polymer brushes. For example, a coating of polymer brushes on a plastic surface such as an artificial heart valve or a dialysis machine can hinder the adsorption of proteins onto the surface. It can also be used in the fabrication of next-generation microelectronic devices. Other areas of application include biocompatible coatings for implants, chemical sensors, and new “intelligent” materials.
Although progress has been made with regard to new brush structures, current methods do not offer sufficient temporal and spatial control over the growth process. Usually, a self-organized monolayer of an initiator is assembled on a substrate and the polymer chains can grow out from there.
In order to obtain specific patterns, the initiator must be applied to the substrate in a corresponding pattern—a complex undertaking that is not manufacturable and does not allow for the generation of complex three-dimensional structures.
Craig J. Hawker and a team from the University of California, Santa Barbara, and The Dow Chemical Company (Midland, Michigan) have developed a new method that allows for the formation of brushes on a uniform initiator layer with both spatial and temporal control. Their simple method is based on a light-activated radical polymerization. The length of the bristles at any given location depends only on the duration and intensity of the local irradiation.
To form a specific structure, conventional photomasks can be used. These have openings in the areas to be irradiated and shield the other areas from the light. This allows for the formation of extensive patterns with submicrometer resolution in one step. All of this is made possible by a special iridium-based photocatalyst. It remains active for only a very short time after irradiation, so it cannot travel very far into nonirradiated areas while in its active state. It is even possible to use a grayscale photomask with continuously increasing opacity to produce gradated patterns.
Another advantage of this new method is that newly incorporated monomers are always added to the chain adjacent to the initiator, meaning that the initiator remains at the forward end of the growing chain. Because it is not destroyed as in other methods, and remains available at the right position, the polymerization can be stopped and restarted at any time. In this way the mask being used can be exchanged as often as desired. It is even possible to vary the monomer being used during the process. The complexity of accessible structures and applications is thus almost unlimited.About the Author
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201301845
Craig J. Hawker | Angewandte Chemie
New therapeutic approach to combat African sleeping sickness
20.02.2019 | Johannes Gutenberg-Universität Mainz
'Butterfly-shaped' palladium subnano cluster built in 3-D
20.02.2019 | Institute of Industrial Science, The University of Tokyo
Up to now, OLEDs have been used exclusively as a novel lighting technology for use in luminaires and lamps. However, flexible organic technology can offer much more: as an active lighting surface, it can be combined with a wide variety of materials, not just to modify but to revolutionize the functionality and design of countless existing products. To exemplify this, the Fraunhofer FEP together with the company EMDE development of light GmbH will be presenting hybrid flexible OLEDs integrated into textile designs within the EU-funded project PI-SCALE for the first time at LOPEC (March 19-21, 2019 in Munich, Germany) as examples of some of the many possible applications.
The Fraunhofer FEP, a provider of research and development services in the field of organic electronics, has long been involved in the development of...
For the first time, an international team of scientists based in Regensburg, Germany, has recorded the orbitals of single molecules in different charge states in a novel type of microscopy. The research findings are published under the title “Mapping orbital changes upon electron transfer with tunneling microscopy on insulators” in the prestigious journal “Nature”.
The building blocks of matter surrounding us are atoms and molecules. The properties of that matter, however, are often not set by these building blocks...
Scientists at the University of Konstanz identify fierce competition between the human immune system and bacterial pathogens
Cell biologists from the University of Konstanz shed light on a recent evolutionary process in the human immune system and publish their findings in the...
Laser physicists have taken snapshots of carbon molecules C₆₀ showing how they transform in intense infrared light
When carbon molecules C₆₀ are exposed to an intense infrared light, they change their ball-like structure to a more elongated version. This has now been...
The so-called Abelian sandpile model has been studied by scientists for more than 30 years to better understand a physical phenomenon called self-organized...
11.02.2019 | Event News
30.01.2019 | Event News
16.01.2019 | Event News
20.02.2019 | Life Sciences
20.02.2019 | Medical Engineering
20.02.2019 | Power and Electrical Engineering