Simulating how polymers arrange dissolved ions Featured

    MPC-CMSE Summer Scholar Kirill Shmilovich conducts computational studies to model how polymers alter the shapes that dissolved ions can form.

    When we imagine crystals, often the first things that come to mind are rock hard matter like diamonds and gemstone quality minerals. But there is another group of materials that are classified as crystals because of their similarly shaped repeating structures at the molecular level that form teeth, bones and other natural living structures. It is in this realm that Alfredo Alexander-Katz, associate professor of materials science and engineering, analyzes how adding polymers affects the way these crystals arrange themselves in solution.

    2017 MPC-CMSE Summer Scholar Kirill Shmilovich uses computer-based computational studies to model how these dissolved ions form crystal structures under the influence of large, squishy polymers, which are positively or negatively charged, and to identify which of these polymers can help to make synthetic versions of desirable natural formations that are difficult to copy.

    “My project focuses on understanding how polymers can help in the clustering of different ionic structures and comparing how ionic structures form passively in water versus how these ionic structures form when polymers are introduced into the system,” Kirill Shmilovich, a rising senior at the University of Wisconsin at Milwaukee, explains. The physics and mathematics major says ions form various crystals with differing shapes, called polymorphs, based on their environment. He is using molecular dynamic simulations, which simulate the atoms within a system, to understand the mechanisms at play when polymers alter the formation of these ionic structures. He also is examining how polymers influence clustering through positive and negative charges between the polymers and the ions.

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    MPC-CMSE Summer Scholar Kirill Shmilovich conducts computational studies to model how polymers alter the shapes that dissolved ions can form, working in the lab of Alfredo Alexander-Katz, associate professor of materials science and engineering at MIT. Photo, Denis Paiste, Materials Processing Center.

    Shmilovich’s summer research is guided by Shayna Hilburg, a graduate student in the Program in Polymers and Soft Matter. “She has helped me understand how the particular software used in this laboratory can help model atoms and molecules on the atomistic scale,” he says. Shmilovich’s simulations have used Alexander-Katz’s computer clusters at MIT as well as a Department of Energy facility. “At my home institution I worked on much more coarse grained and larger scale systems for longer time periods, and here I'm learning much more on the atomistic approach and how things are done in very short time periods,” Shmilovich says.

    Hilburg notes that “The work that Kirill is doing here of looking at the ions aggregating in solution when the polymer is present is going to help in a broader project that we have in the Alexander-Katz group where we are looking at how polymers can in general change the aggregation of ions as they assemble into crystals and they can assemble in specific orders that create different crystals for different structures.”

    “We're going to use this information that Kirill makes and that data will be directly applicable to the next steps in the project, specifically crystals that are relevant for biomineralization, the formation of teeth or bones or shells,” Hilburg continues. “This is relevant as well for pharmaceutical companies who do the crystallization of drugs, so that they can form pills out of the drugs that they create, and a lot of different techniques that use organic molecules in the presence of ions to kinetically change what shapes the crystals make.”

    While working in Alexander-Katz’s Laboratory for Theoretical Soft Materials, Shmilovich explains, “What we're doing here is we have polyacrylic acid, a negatively charged polymer, in a system with water and counter ions to neutralize the charges in the system. Here we're letting the system relax into a steady state, after which, we will add additional calcium and carbonate ions, where we can then see how the polymer helps clustering of these calcium and carbonate ions into different crystalline structures.” Calcium carbonate is the active ingredient in several commonly used antacids for upset stomach.

    “In this research experience, I gained a valuable opportunity to work with people outside of my home institution and learn new techniques and practices that I would previously not have known, and how these different techniques and practices can be applied to fields outside my own,” Shmilovich says.

    Shmilovich’s internship is supported in part by NSF’s Materials Research Science and Engineering Centers program [grant DMR-14-19807]. Participants in the Research Experience for Undergraduates, co-sponsored by the Materials Processing Center and the Center for Materials Science and Engineering, presented their results at a poster session during the last week of the program. The program ran from June 15, 2017, to August 5, 2017, on the MIT campus in Cambridge, Mass.

    Denis Paiste, Materials Processing Center
    August 28, 2017

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    Summer Scholar Kirill Shmilovich Trio Poster 9208 DP Web
    MIT bioengineering graduate students [from left] Julie Takagi, Caroline Werlang and Jacob Witten, listen to MPC-CMSE Summer Scholar Kirill Shmilovich discuss his project modeling how polymers alter the possible shapes that dissolved ions form. Photo, Denis Paiste, Materials Processing Center.