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
Making fuel out of thick air
08.12.2017 | DOE/Argonne National Laboratory
‘Spying’ on the hidden geometry of complex networks through machine intelligence
08.12.2017 | Technische Universität Dresden
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
Transistors based on carbon nanostructures: what sounds like a futuristic dream could be reality in just a few years' time. An international research team working with Empa has now succeeded in producing nanotransistors from graphene ribbons that are only a few atoms wide, as reported in the current issue of the trade journal "Nature Communications."
Graphene ribbons that are only a few atoms wide, so-called graphene nanoribbons, have special electrical properties that make them promising candidates for the...
08.12.2017 | Event News
07.12.2017 | Event News
05.12.2017 | Event News
08.12.2017 | Life Sciences
08.12.2017 | Information Technology
08.12.2017 | Information Technology