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Polymers that fold and unfold under UV light

Credit: Angewandte Chemie

Polymers, which are the basis of all plastics, usually do not have a regular structure, in contrast to biopolymers such as proteins. A team of researchers has now developed a polymer that can be distinguished into folded (ordered) and unfolded (disordered) domains using UV irradiation.The work of the team offers new possibilities for developing functional soft materials, as they write in the journal. Angewandte Chemie..


Protein is long Molecular chain It can fold, twist, and form unordered clusters. The placement of domains in different orders within a protein gives the protein its ultimate form and therefore functions. However, what happens simply and ubiquitously in nature is not always easy to reproduce in the lab. It is difficult to give a chain polymer, such as a polymer, a form other than an unordered cluster.

An international research team led by Shiki Yakai of Chiba University in Japan and Giovanni M. Pavan of Polytechnico di Torino in Turin, Italy, has differentiated a particular class of polymers known as supramolecular polymers. I found a folding system.of Supramolecular polymer, The monomers in the chain are not directly linked by chemical bonds.Instead, they are held together by unbound interactions such as electrostatic forces, providing researchers with interesting tools to manipulate. structure of polymer After its formation.

The research team built a supramolecular polymer from monomers that stack six-member rosettes to form an infinitely long chain, a supramolecular polymer chain. Due to the inherent curvature created along the stacked rosettes, the nanofibers were twisted and folded into a spiral structure. You can remove the fold by triggering the “light switch”. Irradiation with UV light causes the monomers to bend, twist the molecules, reduce the rotation of the rosette, and develop a helical structure.

To prevent the entire polymer from spreading evenly, researchers have also adopted a second switch that works using temperature. The slightly stiffer monomer made it possible to maintain the curvature of the polymer chain. The heating then unfolded the polymer in a non-uniform and coordinated manner, resulting in a state of reacting to UV irradiation.

As the blocks unfolded one after another, researchers reported that prolonged irradiation and heat retention of the polymer shortened the spiral blocks until the entire structure was reduced to chaotic clusters. This expansion mechanism was confirmed by molecular simulation. The authors found that the results obtained from computer modeling indicate that the isomerization that occurs in the more or less ordered domain within the assembly is the starting point for the separation of supramolecular polymers into folded and unfolded regions. It suggests that it indicates that it can be.

By this study Supramolecular Polymer to folded and unfolded areas. You can add more functionality to such blocks and change their interaction with the environment. The authors state that this may open up new possibilities for nanofabrication of functional soft materials.


Supramolecular polymer length control


For more information:
Keigo Tashiro et al., Non-uniform photoinduced unfolding of supramolecular polymers leading to topological block nanofibers, Angewandte Chemie International Edition (2021). DOI: 10.1002 / anie.202110224

Quote: The polymer that folds and unfolds under UV light (November 30, 2021) is available from https: //phys.org/news/2021-11-polymer-unfolds-uv.html on November 30, 2021. Obtained

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Polymers that fold and unfold under UV light

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