Wednesday, July 27, 2022

Shape-Memory Polymers

Ilya Starodumov as a member of an international team, is developing a technology for creating "smart" polymers.
Credit: Ilya Safarov

Biocompatible polymers based on a "smart" material poly (ε-caprolactone) that keeps its shape may appear in Russia. An international team of scientists from Russia, Israel, and Japan, including physicists from Ural Federal University, work on the technology of its creation. The research is supported by the Russian Foundation for Basic Research.

Polymeric materials based on poly (ε-caprolactone) are suitable for biomedical purposes: for surgery, cell engineering, regenerative medicine. Such material can be used to make devices for minimally invasive surgery (with minimal incisions), self-tightening surgical sutures, etc. A description of this material was published in The Journal of Physical Chemistry B.

"A special feature of polymers with shape memory is the ability to return to the original shape when the temperature changes. It looks like this: a polymer product with a certain "programmed" shape is made. Then this product is deformed in any manner, for example, stretched or curled, like surgical sutures. When heated to a certain temperature, the memory mechanism in the polymer is activated at the molecular level, and the product restores its original shape," says Ilya Starodumov, Head of the Laboratory of Multiphase Physico-Biological Environment Simulation at UrFU.

The production of poly(ε-caprolactone) is carried out by several major world centers, around which, as a rule, the engineering and chemical industry for the production of goods from this raw material is lined up. In Russia poly(ε-caprolactone) production is underdeveloped, and scientists note that research may increase interest in the development of such polymers in general and specific goods made from them in particular.

The Ural scientists' contribution to the development is in simulation. Physicists created a computer simulation of the molecular structure of the polymer, which improved the characteristics of the material and the technology of its production at the molecular level.

"Our part of the work is to virtually simulate polymerization at the molecular level. This is necessary in order to study in detail the process of "crosslinking" individual macromonomers into a polymer network. In this way we study the technological process of creating a polymer at the level of individual molecules," Starodumov explains.

When creating a computer molecular model, it is important to accurately select the so-called force field that is a set of force characteristics of atoms that determine how they interact with each other and with the environment, the physicist adds. If the atoms in a molecule are connected by springs, the force fields are the characteristics of these springs. The scientists' task is to compare alternative force fields as applied to molecules and choose the best of them.

"The right force field allowed us to determine that this material had the characteristic qualities of a semi-crystalline polymer with suitable thermodynamic characteristics for future products. Initially, we believed that biopolymers could be modeled using the optimized potentials for liquid simulations force field, widely used to describe protein chains. By comparing the developed optimized potentials for liquid simulations model with a model that uses a more traditional force field for such tasks, as well as with experimental data, we were able to confirm the hypothesis," adds Ilya Starodumov.

As a result, the Ural physicists' simulation can both explain polymer characteristics under different conditions and predict material properties when the synthesis technology is changed or when interacting with biological environments.

Ural scientists will continue their work on the development of molecular simulations. The next stage of research will be simulation of the characteristics of an already "cross-linked" polymer network.

Source/Credit: Ural Federal University

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