Researchers have combined a polymer material with the shape of a common kitchen tool to help better control the design and application of coatings for various products and surfaces. A team at Rice University’s Brown School of Engineering developed a technique that shows how microscopic bottlebrush polymers are drawn to the top and bottom of a coating applied to a surface. The discovery could lead to a way to customize the properties of coatings for specific applications.

Rice University graduate student Hao Mei holds a plate with a pattern of bottlebrush polymers spelling “RICE.” The microscopic polymers could give industry exquisite control over the properties of surface coatings. (Image source: Jeff Fitlow)

The research was led by Rafael Verduzco, an associate professor and chemical and biomolecular engineer at Rice who has been studying so-called bottlebrush copolymers for some time. He and his collaborators now have developed models and methods to refine surface coatings to make them, for instance, more waterproof or more conductive, depending on what an application demands.

Coatings are a key interest for Verduzco because they can be the difference between a successful product and one that fails, he said. “Coatings are ubiquitous,” he said in a press statement. “If we didn’t have the right coatings, our materials would degrade quickly. They would react in ways we don’t want them to.”

Because of this, coating a surface is a separate and different way of thinking than the product itself. Therefore, different processes have to be applied to this part of creating something new, he said. “You make something and then you have to find a way to deposit a coating on top of it,” said Verduzco.

Same name, different use

Resembling the kitchen implements of the same name, bottlebrushes consist of small polymer chains that radiate outward from a linear polymer rod.  The bottlebrushes self-assemble in a solution, which researchers than can work with to adjust their properties. “What we’re looking at is a kind of universal additive, a molecule you can blend with whatever you’re making that will spontaneously go to the surface or the interface,” said Verduzco. “That’s how we ended up using bottlebrushes.”

What researchers discovered in their work is that bottlebrushes mixed with linear polymers tend to migrate to the top and bottom of a thin film as it dries. These films, as coatings, are ubiquitous in products; for instance, they are currently used as waterproof layers to keep metals from rusting or fabrics from staining.

During this migration, the linear polymers hold the center while the bottlebrushes migrate to the air above or to the substrate below. This, in effect, decouples the properties of the coating from its exposed surfaces. “The chemistry of these materials is advanced sufficiently that you can pretty much put just about any kind of polymer as one of these bristles on the side chain,” said Verduzco. “You can put them in different order.”

Researchers published a paper on their work in the American Chemical Society journal Macromolecules.

The team conducted computational models and experiments demonstrating that variations in the bottlebrush itself could be used to control surface characteristics, making these polymers useful in coating applications.

Applications for these materials include drug delivery via functionalized bottlebrushes that form micelles; lubricants; soft elastomers; and even surfaces that heal themselves. However, one challenge researchers still face is that bottlebrush polymers are still difficult to make in bulk.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

With processors getting smaller and smaller while requiring more processing power, silicon is reaching the limits of its ability to meet the needs of future chips.

Unlike other materials with electrons that scatter in many directions, the electrons in 2D antimony can be made to move together in an orderly way, giving it a high charge mobility and making the material an efficient semiconductor. (Image source: The University of Texas at Austin)

Consequently, researchers have been searching for new materials that can replace silicon while still packing a lot of processing power into a tiny punch. Assistant professor Yuanyue Liu and a research team at The University of Texas at Austin (UT) Cockrell School of Engineering have found a solution in an existing semi-metal: antimony.

The team, which also includes UT postdoctoral fellow Long Cheng and graduate student Chenmu Zhang, published a paper on their work in the Journal of the American Chemical Society.

Liu, an assistant professor of mechanical engineering, said, in its 2D form, antimony shows promise as a semiconducting material for smaller chips. For one, antimony is only a couple of atomic layers thick while still having a high charge mobility, or speed with which a charge moves through the material when being pulled by an electric field. 2D antimony also has a significantly higher charge mobility than silicon, said Liu. This gives it strong potential as a building block for next-generation processors.

Antimony has already proven its worth in electronics for some semiconductor devices, such as infrared detectors. The UT researchers believe this use can be extended to future devices as well.

So far 2D antimony’s semiconducting potential has only been proven through theoretical computation. The team’s next step is to test the properties of the material with physical antimony samples.

The team’s work has broader implications; since researchers have seen antimony’s viability as a semiconductor for future devices, they also know why the material carries charge so quickly. “We have uncovered the physical origins of why antimony has a high mobility,” Liu said in a press statement.  “These findings could be used to potentially discover even better materials.”

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.