Impact of Radical Polymer Architecture on Spin Transport

Non-Technical Summary

Advances in computing have revolutionized the way the world operates, communicates, and does business; however, due to outstanding technological breakthroughs and visionary implementation, the current microelectronics paradigm is reaching its upper limit of computing performance. As such, new operational paradigms, which will rely on the development of novel materials, must be discovered, developed, and matured such that these critical technologies continue to evolve.

One promising thrust in pushing this idea towards reality is that of spin-based quantum computing. In this context, spin refers to an inherent property of electrons that is distinct from the inherent charge that is often used to conduct electrons (i.e., an electric current), and it is a property that can be manipulated such that there is transport of spin (i.e., a spin current).

This project, with support from the Polymers program in NSF’s Division of Materials Research, develops new polymer materials that are anticipated to have advanced spin transport properties. In addition to providing systems with performance that is potentially better than the current state of the art, using polymers as the spin-transport material opens the opportunity of creating low-cost solutions to this technology opportunity.

Therefore, successful execution of the project could lead to next-generation quantum computing materials that are readily integrated into device infrastructures. Furthermore, the educational and outreach components of the project provide unique experiences to a diverse group of scientists and engineers with an aim of broadening participation in science and engineering.

In addition to providing summer research opportunities to high school students from economically-diverse backgrounds and undergraduate students, graduate student researchers on this project participate in a domestic trainee exchange program to advance their technical skills. Additionally, a new massive open online course (MOOC) based on the specific class of polymers utilized in this program is offered such that the results are communicated to a broad audience in a rapid and digestible manner.

In these ways, the project pushes the bounds of fundamental science such that it offers clear translation to new technologies and new educational programs that advance national prosperity and national defense. Technical Summary

The polymer science community has contributed to advancing organic electronic materials for multiple end-use applications. As such, much effort has been placed in elucidating the fundamental underpinnings associated with the chemistry and physics of these macromolecules; however, the ability to apply these same polymer science tools to manipulate spin transport in macromolecular materials is not at the same level.

Moreover, most of the work in the community has focused on conjugated polymers given the history of the field and the good deal of success these materials have had in advancing key device technologies. On the other hand, radical polymers (i.e., nonconjugated macromolecules with stable open-shell sites present at their pendant groups) are a new class of spin-transporting organic materials and differ in two key ways relative to most spin transport materials.

First, the carbon-based nature of these polymer conductors causes them to possess weak spin-orbit couplings, higher spin relaxation times, and long spin diffusion lengths (i.e., > 50 nm) relative to many of their inorganic counterparts, and these materials characteristics are essential for enhanced spin transport. Additionally, radical polymers offer a different spin transport environment compared to most of their conjugated polymer counterparts.

That is, the inherent nature of their stable open-shell pendant sites ensures that spin transport occurs through a paramagnetic medium, which could enhance the spin diffusion length. To these points, this project, supported by the Polymers program in NSF’s Division of Materials Research, establishes the underlying structure-property-performance relationships associated with the macromolecular architecture, nanostructural environment, magnetic environment, and spin transport properties of radical polymers.

Furthermore, this project advances the local American Chemical Society (ACS) Project SEED Program, which provides summer research opportunities to high school students from economically-disadvantaged backgrounds. Moreover, it provides for a means by which to have a student exchange with a leading polymer synthesis group in the United States such that cross-training of chemical engineering graduate students occurs.

Finally, the project includes the development of a MOOC describing radical polymer fundamentals, because a course like this does not exist currently. Therefore, the project has the potential to make inroads in terms of fundamental scientific and broader impact while also supporting educational and outreach activities.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.