A 3D rendering illustrating 2 monomers forming a reversible double-hydrogen bond that slows down polymer movement without creating a flexible network. Credit: S. Nian et al., Phys.
A research study team led by the University of Virginia has actually carried out a study on associative polymers, a kind of material with special self-healing and properties, which appears to challenge a long-held understanding of how the materials operate at the molecular level.
The study was led by Liheng Cai, an assistant professor of materials science and engineering and chemical engineering at UVA. Cai stated that this new discovery holds considerable significance due to the myriad of applications these products have in life, ranging from engineering of recyclable plastics, to human tissue engineering, and even manipulating the viscosity of paint to prevent it from dripping.
The discovery, which has been published in the journal Physical Review Letters, was made it possible for by new associative polymers developed in Cais lab at the UVA School of Engineering and Applied Science by his postdoctoral researcher Shifeng Nian and Ph.D. trainee Myoeum Kim. The development progressed from a theory Cai had actually co-developed before coming to UVA in 2018.
As an outcome, associative polymers provide services to some of the most pressing challenges in sustainability and health. Associative polymers are utilized as viscosity modifiers in fuels, to produce tough self-healing polymers, and to engineer biomaterials with physical residential or commercial properties crucial to tissue engineering and regrowth.
In nearly all existing experimental systems, the moieties aggregate into small clusters, which avoids an exact research study of the relationship in between reversible bonds and polymer habits.
Cais team established brand-new types of associative polymers where the bonds are uniformly dispersed throughout the material and at a large variety of densities. A National Science Foundation CAREER award supports Cais research on associative polymers.
” Shifeng and Myoeum basically created an unique experimental platform to study the dynamics of associative polymers in methods that werent possible before,” Cai said.
” This gave us a new perspective on the polymers habits and provides opportunities to improve our understanding of especially difficult locations of study in polymer science. And from an innovation standpoint, the research adds to the advancement of self-healing materials with customized properties.”
Polymers are macromolecules composed of duplicating units, or monomers. By rearranging or combining these systems and playing with their bonds, researchers can create polymeric products with specific qualities.
Polymers likewise can alter states, from hard and stiff, like glass, to rubbery and even fluid depending on factors such as temperature level or force– for instance, pressing a strong gel through a hypodermic needle.
Associative polymers are especially distinctive: Their moieties– a general term for molecular subunits with adjustable physical homes– are held together by reversible bonds, indicating they can break apart and re-form.
This procedure enables macroscopic residential or commercial properties unattainable by standard polymers. As a result, associative polymers offer solutions to some of the most pressing difficulties in sustainability and health. Associative polymers are used as viscosity modifiers in fuels, to create hard self-healing polymers, and to engineer biomaterials with physical residential or commercial properties important to tissue engineering and regeneration.
One key to the UVA groups work was conquering a material feature that has actually stymied scientists for years. In the lab, researchers work with products whose bonds can break and re-form at “laboratory time scales,” suggesting within time frames they can observe through experiments. Nevertheless, in almost all existing speculative systems, the moieties aggregate into small clusters, which prevents an accurate study of the relationship between reversible bonds and polymer behavior.
Cais group established new kinds of associative polymers where the bonds are equally distributed throughout the product and at a wide variety of densities. To verify that their products do not form clusters, the scientists collaborated with Mikhail Zhernenkov, a researcher at the U.S. Department of Energys Brookhaven National Laboratory. They conducted experiments using a sophisticated X-ray tool– the soft matter interfaces beamline– at the National Synchrotron Light Source II to expose the inner makeup of the polymers without harming the samples.
These new associative polymers enabled Cais group to precisely study the effects of reversible interactions on the characteristics of associative polymers.
Dynamics and habits describe qualities such as the temperature at which particle movement slows to a stiff “glassy” state, viscosity (how easily a product streams), and flexibility (its ability to snap back after being de-formed). A mix of these characteristics is often preferable to style, for instance, a biomaterial compatible with human tissue that can reconstitute itself after injection.
For 30 years, it had been accepted that when the reversible bonds stay undamaged, they function as crosslinkers, leading to a rubbery product. Thats not what the UVA-led team discovered.
Teaming Up with Shiwang Cheng, an assistant teacher in Michigan State Universitys chemical engineering and products science department and an expert in flow characteristics, the team precisely measured the circulation behavior of their polymers in a wide variety of time scales.
” This requires mindful control over the regional environment, such as temperature and humidity of the polymers,” Cheng stated. “Over the years, my laboratory has developed a set of methods and systems for doing so.”
The group discovered that the bonds can decrease polymer motion and dissipate energy without developing a rubbery network. Suddenly, the research showed that reversible interactions influence the polymers glassy qualities rather than their viscoelastic range.
” Our associative polymers provide a system that allows for investigating independently the impacts of reversible interactions on [polymer] motion and glassy habits,” Cai said. “This might provide opportunities to enhance the understanding of the tough physics of glassy polymers like plastics.”
From their experiments, Cais group also established a brand-new molecular theory that discusses the behavior of associative polymers, which might shift thinking of how to craft them with optimized properties such as high tightness and fast self-healing capability.
Recommendation: “Dynamics of Associative Polymers with High Density of Reversible Bonds” by Shifeng Nian, Shalin Patil, Siteng Zhang, Myoeum Kim, Quan Chen, Mikhail Zhernenkov, Ting Ge, Shiwang Cheng and Li-Heng Cai, 31 May 2023, Physical Review Letters.DOI: 10.1103/ PhysRevLett.130.228101.
In addition to Nian, Kim, Cheng and Zhernenkov, Cai collaborated with Ting Ge, a computational simulations professional and assistant professor of chemistry and biochemistry at the University of South Carolina, and Quan Chen from the State Key Lab of Polymer Physics and Chemistry at the Changchun Institute of Applied Chemistry, who provided the initial code for analyzing the circulation habits of polymers.
The paper, “Dynamics of Associative Polymers with High Density of Reversible Bonds,” appears in the June 2 problem of Physical Review Letters, the flagship publication of the American Physical Society, and is included as an Editors Suggestion– a difference offered to just one in 6 accepted letters. It likewise is featured as a lead article in Physics, the societys online publication.
A National Science Foundation CAREER award supports Cais research study on associative polymers. He likewise receives funding from UVA, including the LaunchPad for Diabetes Fund. His research study team is continuing to deal with establishing the clinical foundation for using these materials.
By University of Virginia School of Engineering and Applied Science
June 28, 2023