Researchers Develop Self-Assembling Materials that Might be Useful in Optical Devices

Saturday, July 6, 2019 - 13:32

MIT researchers have developed self-assembling materials which can be formed into much more complex patterns so will open up new areas of materials design.

The research, appeared in the journal Nature Communications, was carried out by postdoc Yi Ding, professors of materials science and engineering Alfredo Alexander-Katz and Caroline Ross, and three others, phys.org reports.

Alexander-Katz describes the team's discovery of a phenomenon that allows the polymers to self-assemble in patterns that deviate from regular symmetrical arrays.

Self-assembling block copolymers are materials whose chain-like molecules, which are initially disordered, will spontaneously arrange themselves into periodic structures.

In the new method, there are two different, mismatched patterns. One is from a set of posts or lines etched on a substrate material, and the other is an inherent pattern that is created by the self-assembling copolymer.

The resulting odd patterns are "a result of the frustration between the pattern the polymer would like to form, and the template," explained Alexander-Katz. That frustration leads to a breaking of the original symmetries and the creation of new subregions with different kinds of symmetries within them, he said.

Having created these novel structures, the team went on to develop models to explain the process. Co-author Karim Gadelrab Ph.D. '19, says, "The modeling work showed that the emergent patterns are in fact thermodynamically stable, and revealed the conditions under which the new patterns would form."

Ding says "We understand the system fully in terms of the thermodynamics," and the self-assembling process "allows us to create fine patterns and to access some new symmetries that are otherwise hard to fabricate."

Researchers said that so far, the work the team has done has been confined to two-dimensional surfaces, but in ongoing work they are hoping to extend the process into the third dimension.

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