Bottlebrushes rise up to control coatings

November 14, 2019

HOUSTON - (Nov. 14, 2019) - A microscopic polymer in the form of a common kitchen implement could give industry exquisite control over coatings.

Bottlebrush copolymers have long been a topic of study for Rafael Verduzco, a chemical and biomolecular engineer at Rice University's Brown School of Engineering. Now, he and his collaborators have developed models and methods to refine surface coatings to make them, for instance, more waterproof or more conductive.

The researchers discovered 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 as waterproof layers to keep metals from rusting or fabrics from staining.

When the migration happens, the linear polymers hold the center while the bottlebrushes are drawn to the air above or the substrate below. This, Verduzco said, effectively decouples the properties of the bulk coating from its exposed surfaces.

Computational models and experiments showed that variations in the bottlebrush itself could be used to control surface characteristics.

Bottlebrush polymers remain challenging to make in bulk, Verduzco said, but their potential uses are vast. Applications could include drug delivery via functionalized bottlebrushes that form micelles, lubricants, soft elastomers, anti-fouling filters and surfaces that heal themselves, he said.

The details appear in the American Chemical Society journal Macromolecules.

The Rice lab, with help from peers at the University of Tennessee, Knoxville; Oak Ridge National Laboratory and the University of Houston, characterized various bottlebrushes made of polystyrene and poly(methyl methacrylate) (aka PMMA) while studying what causes the polymers to migrate.

Resembling their macro kitchen cousins (as well as certain flowers), bottlebrushes consist of small polymer chains that radiate outward from a linear polymer rod. The bottlebrushes self-assemble in a solution, which can be manipulated to adjust their properties.

Coatings are ubiquitous, Verduzco said. "If we didn't have the right coatings, our materials would degrade quickly," he said. "They would react in ways we don't want them to. So coating a surface is usually a separate process; you make something and then you have to find a way to deposit a coating on top of it.

"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," he said. "That's how we ended up using bottlebrushes."

Bottlebrushes can be tuned by varying the number of side chains, their length or the length of the backbone polymer, Verduzco said. The side chains themselves can be of mixed type, and small molecules or proteins can be added to their end groups.

"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," he said. "You can put them in different order."

The researchers found entropic and enthalpic thermodynamics drove bottlebrushes almost completely away from the interior of the films and toward the interfaces as they dried. Even where linear polymers were designed to pair with the surface interface, the bottlebrushes still rose to the exposed surface.

Verduzco noted the findings were made possible by the time of flight-secondary ion mass spectrometer acquired by Rice in 2018 through a National Science Foundation grant. The spectrometer allowed the researchers to characterize not only the surface of coatings by bombarding them with ions, but also how coatings changed as microscopic layers were removed from the top down.
-end-
Rice graduate student Hao Mei is lead author of the paper. Co-authors are Rice research assistant Jiabei Li and research specialist Tanguy Terlier; graduate student Travis Laws of the University of Tennessee; postdoctoral researcher Jyoti Mahalik of the University of Tennessee and Oak Ridge National Laboratory; Rice and University of Houston alumna Adeline Mah, now at Element Biosciences, San Diego; and researcher Peter Bonnesen and technician David Uhrig of Oak Ridge.

Research scientist Rajeev Kumar of Oak Ridge and Gila Stein, the Prados Associate Professor of Chemical and Biomolecular Engineering at the University of Tennessee, are co-principal investigators. Verduzco is an associate professor of chemical and biomolecular engineering and of materials science and nanoengineering.

The National Science Foundation, Welch Foundation and the Department of Energy Office of Science supported the research.

Read the abstract at https://pubs.acs.org/doi/10.1021/acs.macromol.9b01801

This news release can be found online at https://news.rice.edu/2019/11/14/bottlebrushes-rise-up-to-control-coatings/

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related materials:

Structure, function, self-assembly and applications of bottlebrush copolymers (review paper): https://pubs.rsc.org/en/content/articlelanding/2015/cs/c4cs00329b#!divAbstract

Verduzco Laboratory: http://verduzcolab.blogs.rice.edu

Rice Department of Chemical and Biomolecular Engineering: https://chbe.rice.edu

Rice Department of Materials Science and NanoEngineering: https://msne.rice.edu

George R. Brown School of Engineering: https://engineering.rice.edu

Images for download:

https://news-network.rice.edu/news/files/2019/11/1125_BOTTLEBRUSH-1-WEB.jpg
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. (Credit: Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2019/11/1125_BOTTLEBRUSH-2-WEB.jpg
A hydrophobic coating of bottlebrush polymers created by Rice University engineers resists a drop of water. Microscopic bottlebrushes can be configured to give coatings specific properties for many applications. (Credit: Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2019/11/1125_BOTTLEBRUSH-3-WEB-1.jpg
Rafael Verduzco, left, a chemical and biomolecular engineer at Rice University, and graduate student Hao Mei led a study that shows 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. (Credit: Jeff Fitlow/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,962 undergraduates and 3,027 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 4 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finan

Jeff Falk
713-348-6775
jfalk@rice.edu

Mike Williams
713-348-6728
mikewilliams@rice.edu

Rice University

Related Polymers Articles from Brightsurf:

Ultraheavy precision polymers
An environmentally friendly and sustainable synthesis of ''heavyweight'' polymers with very narrow molecular weight distributions is an important concept in modern polymer chemistry.

FSU researchers help develop sustainable polymers
Researchers at the FAMU-FSU College of Engineering have made new discoveries on the effects of temperature on sustainable polymers.

Structural colors from cellulose-based polymers
A surface displays structural colors when light is reflected by tiny, regular structural elements in a transparent material.

Growing polymers with different lengths
ETH researchers have developed a new method for producing polymers with different lengths.

Exciting new developments for polymers made from waste sulfur
Researchers at the University of Liverpool are making significant progress in the quest to develop new sulfur polymers that provide an environmentally friendly alternative to some traditional petrochemical based plastics.

Polymers can fine-tune attractions between suspended nanocubes
In new research published in EPJ E, researchers demonstrate a high level of control over a type of colloid in which the suspended particles take the form of hollow, nanoscale cubes.

Functional polymers to improve thermal stability of bioplastics
One of the key objectives for contemporary chemistry is to improve thermomechanical properties of polymers, in particular, thermostability of bioplastics.

Fluorescent technique brings aging polymers to light
Modern society relies on polymers, such as polypropylene or polyethylene plastic, for a wide range of applications, from food containers to automobile parts to medical devices.

Polymers to the rescue! Saving cells from damaging ice
Research published in the Journal of the American Chemical Society by University of Utah chemists Pavithra Naullage and Valeria Molinero provides the foundation to design efficient polymers that can prevent the growth of ice that damages cells.

Mixing the unmixable -- a novel approach for efficiently fusing different polymers
Cross-linked polymers are structures where large molecular chains are linked together, allowing exceptional mechanical properties and chemical resistance to the final product.

Read More: Polymers News and Polymers Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.