{"599811":{"#nid":"599811","#data":{"type":"news","title":"Perking Up and Crimping the \u2018Bristles\u2019 of Polyelectrolyte Brushes","body":[{"value":"\u003Cp\u003EIf the bristles of a brush abruptly collapsed into wads of noodles, the brush would, of course, become useless. When it\u0026rsquo;s a micron-scale brush called a \u0026ldquo;polyelectrolyte brush,\u0026rdquo; that collapse could put a promising experimental drug or lubricant out of commission.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EBut now \u003Ca href=\u0022http:\/\/advances.sciencemag.org\/content\/3\/12\/eaao1497\u0022 target=\u0022_blank\u0022\u003Ea new study reveals, in fine detail\u003C\/a\u003E, things that make these special bristles collapse -- and also recover. The research increases understanding of these chemical brushes that have many potential uses.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u003Cstrong\u003EWhat are polyelectrolyte brushes?\u003C\/strong\u003E\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EPolyelectrolyte brushes look a bit like soft bushes, such as shoeshine brushes, but they are on the scale of large molecules and the \u0026ldquo;bristles\u0026rdquo; are made of \u003Ca href=\u0022https:\/\/en.wikipedia.org\/wiki\/Polymer\u0022 target=\u0022_blank\u0022\u003Epolymer chains\u003C\/a\u003E. Polyelectrolyte brushes have a backing, or substrate, and the polymer chains tethered to the backing like soft bristles have chemical properties that make the brush potentially interesting for many practical uses.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EBut polymers are stringy and tend to get tangled or clumped, and keeping them straightened out, like soft bristles, is vital to the function of these micron brushes. Researchers at the Georgia Institute of Technology, the University of Chicago, and the Argonne National Laboratory devised experiments that caused polyelectrolyte brush bristles to collapse and then recover from the collapse.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThey imaged the processes in detail with highly sensitive \u003Ca href=\u0022https:\/\/en.wikipedia.org\/wiki\/Atomic_force_microscopy\u0022 target=\u0022_blank\u0022\u003Eatomic force microscopy\u003C\/a\u003E, and they constructed simulations that closely matched their observations. Principal investigator Blair Brettmann from Georgia Tech and the study\u0026rsquo;s first authors Jing Yu and Nicholas Jackson from the University of Chicago \u003Ca href=\u0022http:\/\/advances.sciencemag.org\/content\/3\/12\/eaao1497\u0022 target=\u0022_blank\u0022\u003Epublished their results on December 8, 2017, in the journal \u003Cem\u003EScience Advances\u003C\/em\u003E\u003C\/a\u003E.\u003C\/p\u003E\r\n\r\n\u003Cp\u003ETheir research was supported by the U.S. Department of Energy, the National Science Foundation, and the Argonne National Laboratory.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u003Cstrong\u003EFrom faux DNA to lubricants\u003C\/strong\u003E\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EThe potential future payoff for the researchers\u0026rsquo; work spans industrial materials to medicine.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EFor example, polyelectrolyte brushes make for surfaces that have their own built-in lubrication. \u0026ldquo;If you attach the brushes to opposing surfaces, and the bristles rub against each other, then they have really low friction and excellent lubrication properties,\u0026rdquo; said Blair Brettmann, who led the study and recently joined Georgia Tech from the University of Chicago.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EPolyelectrolyte brushes could also one day find medical applications. Their bristles have been shown to simulate DNA and encode simple proteins. Other brushes could be engineered to repel bacteria from surfaces. Some polyelectrolyte brushes already exist in the body on the surface of some cells.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EPolyelectrolyte brushes can do so many different things because they can be engineered in so many variations.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026ldquo;When you build the brushes, you have a lot of control,\u0026rdquo; said Brettmann, who is an \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/content\/brettmann\u0022 target=\u0022_blank\u0022\u003Eassistant professor in Georgia Tech\u0026rsquo;s School of Materials Science and Engineering\u003C\/a\u003E. \u0026ldquo;You can control on the nanoscale how far apart the polymer chains (the bristles) are spaced on the substrate and how long they are.\u0026rdquo;\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u003Cstrong\u003EThey\u0026rsquo;re intricate and sensitive\u003C\/strong\u003E\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EFor all their great potential, polyelectrolyte brushes are also complex and sensitive, and a lot of research is needed to understand how to optimize them.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThe polymer chains have positive and negative ionic, or electrolytic, charges alternating along their lengths, thus the name \u0026ldquo;polyelectrolyte.\u0026rdquo; Chemists can string the polymers together using various chemical building blocks, or monomers, and design nuanced charge patterns up and down the chain.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThere\u0026rsquo;s more complexity: Backing and bristles are not all that make up polyelectrolyte brushes. They\u0026rsquo;re bathed in solutions containing gentle electrolytes, which create a balanced ionic pull from all sides that props the bristles up instead of letting them collapse or entangle.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026ldquo;Often these mixtures have a bunch of other stuff in them, so the complexity of this makes it really hard to understand fundamentally,\u0026rdquo; Brettmann said, \u0026ldquo;and thus hard to be able to predict behavior in real applications.\u0026rdquo;\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u003Cstrong\u003EInvading impurities\u003C\/strong\u003E\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EWhen other chemicals enter into these well-balanced systems that make up polyelectrolyte brushes, they can make the bristles collapse. For example, the addition of very powerful electrolytes can act like a flock of wrecking balls.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EIn their experiment, Brettmann and her colleagues used a powerful ionic compound built around yttrium, a rare earth metal with a strong charge. (The ion was trivalent, or had a valence of 3.) The ionic forces from just a low dose of the yttrium electrolyte made the polymer bristles curl up like clumps of sticky spaghetti.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThen the researchers increased the concentration of the gentler ions, which restored support, propping the bristles back up. Atomic force microscope imaging revealed highly regular patterns of collapse and re-extension.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThese patterns were reflected well in the simulations; the reliability of the effects of the ions on collapse and recovery even more so. The ability to build such an accurate simulation reflects the strong consistency of the chemistry, which is good news for potential future research and practical applications.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u003Cstrong\u003EUseless becomes useful\u003C\/strong\u003E\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EFor all the dysfunction that bristle collapses can cause, the ability to collapse them on purpose can be useful. \u0026ldquo;If you could collapse and reactivate the bristles systematically, you could adjust the degree of lubrication, for example, or turn lubrication on and off,\u0026rdquo; Brettmann said.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThe brushes also could regulate chemical reactions involving micro- and nanoparticles by extending and collapsing the bristles.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026ldquo;Coatings and films are often made by carefully combining engineered particles, and you can use these brushes to keep these particles suspended and separate until you\u0026rsquo;re ready to let them meet, bond, and form the product,\u0026rdquo; Brettmann said.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EWhen the polyelectrolyte brush\u0026rsquo;s bristles are extended, they act as a barrier to hold the particles apart. Collapse the bristles out of the way on purpose, and the particles can come together.\u003C\/p\u003E\r\n\r\n\u003Ch4\u003E\u003Cstrong\u003EIt\u0026rsquo;s a nasty world\u003C\/strong\u003E\u003C\/h4\u003E\r\n\r\n\u003Cp\u003EThe experiments were performed with very clean, robust, and uniform compounds unlike the jumble of chemicals that can exist in natural or even industrial systems.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026ldquo;The bristles we used were polystyrene sulfonate, which is a very strong polyelectrolyte, not sensitive to pH or much else,\u0026rdquo; Brettmann said. \u0026ldquo;Biopolymers like polysaccharides, for example, are a lot more sensitive.\u0026rdquo;\u003C\/p\u003E\r\n\r\n\u003Cp\u003ELike many experiments, this one was a departure from real-world conditions. But by creating a foundation for understanding how these systems work, Brettmann wants eventually to be able to move on to sensitive scenarios to realize more of polyelectrolyte brushes\u0026rsquo; practical potential.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Ca href=\u0022http:\/\/www.rh.gatech.edu\/news\/597073\/paper-based-supercapacitor-uses-metal-nanoparticles-boost-energy-density\u0022 target=\u0022_blank\u0022\u003EAlso READ: Paper-based supercapacitor\u0026nbsp;\u003C\/a\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cem\u003EThe study was co-authored by Xin Xu, Marina Ruths, Juan de Pablo and Matthew Tirrell. The research was funded by the U.S. Department of Energy Office of Science, Program in Basic Energy Sciences, Materials Sciences and Engineering Division, the National Science Foundation\u0026rsquo;s Division of Civil, Mechanical, and Manufacturing Innovation (grants 1562876 and 1161475), the Argonne National Laboratory Maria Goeppert Mayer Named AQ41Fellowship. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those sponsors.\u003C\/em\u003E\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA molecular-sized brush that looks like a shoe brush has properties with great potential for the materials industry and medicine, but polyelectrolyte brushes can be sensitive, and getting them to work right tricky. New research shows what can make them break down, but also what can\u0026nbsp;get them to systematically recover.\u003C\/p\u003E\r\n","format":"limited_html"}],"field_summary_sentence":[{"value":"A brush that\u0027s like a shoe brush on a micron scale can have great potential uses for industry and medicine -- but only if it works right."}],"uid":"31759","created_gmt":"2017-12-12 19:48:48","changed_gmt":"2019-01-14 23:17:41","author":"Ben Brumfield","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2017-12-12T00:00:00-05:00","iso_date":"2017-12-12T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"599810":{"id":"599810","type":"image","title":"Polyelecrolyte brushes collapsed and extended","body":null,"created":"1513107066","gmt_created":"2017-12-12 19:31:06","changed":"1513107066","gmt_changed":"2017-12-12 19:31:06","alt":"","file":{"fid":"228671","name":"PE brushes.jpeg","image_path":"\/sites\/default\/files\/images\/PE%20brushes.jpeg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/PE%20brushes.jpeg","mime":"image\/jpeg","size":449813,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/PE%20brushes.jpeg?itok=1-q_vR7y"}},"599808":{"id":"599808","type":"image","title":"Blair Brettmann","body":null,"created":"1513105852","gmt_created":"2017-12-12 19:10:52","changed":"1521037869","gmt_changed":"2018-03-14 14:31:09","alt":"","file":{"fid":"228669","name":"Blair.AFM_.seat_.sm_.jpg","image_path":"\/sites\/default\/files\/images\/Blair.AFM_.seat_.sm_.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/Blair.AFM_.seat_.sm_.jpg","mime":"image\/jpeg","size":3431146,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/Blair.AFM_.seat_.sm_.jpg?itok=bdhc-3Uz"}},"599809":{"id":"599809","type":"image","title":"Blair Brettmann polyelectrolyte brushes, standing at AFM","body":null,"created":"1513106015","gmt_created":"2017-12-12 19:13:35","changed":"1513111829","gmt_changed":"2017-12-12 20:50:29","alt":"","file":{"fid":"228670","name":"Blair.AFM_.stand_.jpg","image_path":"\/sites\/default\/files\/images\/Blair.AFM_.stand_.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/Blair.AFM_.stand_.jpg","mime":"image\/jpeg","size":3657637,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/Blair.AFM_.stand_.jpg?itok=9NlEEwlz"}}},"media_ids":["599810","599808","599809"],"groups":[{"id":"1214","name":"News Room"},{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"135","name":"Research"},{"id":"141","name":"Chemistry and Chemical Engineering"},{"id":"145","name":"Engineering"}],"keywords":[{"id":"176496","name":"polyelectrolyte"},{"id":"176499","name":"ytterium"},{"id":"176500","name":"lubricant"},{"id":"176501","name":"microbe resistance"}],"core_research_areas":[{"id":"39471","name":"Materials"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EWriter and Media Representative\u003C\/strong\u003E: Ben Brumfield\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EMobile: \u003C\/strong\u003E(404-660-1408)\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003Cbr \/\u003E\r\n177 North Avenue\u003Cbr \/\u003E\r\nAtlanta, Georgia \u0026nbsp;30332-0181 \u0026nbsp;USA\u003C\/strong\u003E\u003C\/p\u003E\r\n","format":"limited_html"}],"email":["ben.brumfield@comm.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}