CAREER: Beyond alignment: novel mechanisms for controlling block copolymer phase behavior using magnetic fields

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

NON-TECHNICAL SUMMARY:

Block copolymers (BCPs) are a class of materials composed of two or more chemically-linked distinct blocks of molecular chains. Such materials are used in drug delivery, adhesives, batteries and electronics. BCPs are attractive for developing these types of advanced materials because they can spontaneously form nanometer-sized structures with well-defined features via a process known as self-assembly. However, to more broadly harness the unique properties of BCPs, their self-assembly and ordering on large lengthscales must be well-controlled. This research aims to uncover new mechanisms underlying creation of new BCP structures using low-intensity magnetic fields, and subsequently harness these findings to develop new BCP materials with tunable properties. In the broader context, this project will provide fundamental knowledge on new methods for assembling and processing BCPs into ordered materials using minimal energy from external fields, potentially providing a more sustainable route for developing advanced materials than traditional processing methods. More broadly, to improve enthusiasm, engagement, and subsequent matriculation in materials-related fields, the project will also employ digital tools, inclusive teaching and lab practices, research-based course content, and lab tours with hands-on demos for students at the high school through graduate levels, with a particular focus on engaging women and students from communities of color.

TECHNICAL SUMMARY:

While block copolymers (BCPs) are attractive for developing advanced materials, practical methods for processing BCPs into materials with long-range order are limited, as techniques like magnetic or electric field alignment are typically unfeasible due to the large required field strengths and limited field-responsive chemistries. This project will determine the mechanisms underlying newly-discovered magnetic field-induced phase formation in weakly diamagnetic BCP solutions that cannot be explained by traditional mechanisms of domain alignment, and employ these findings to develop new BCP materials with ordering over large lengthscales. The central hypothesis posits that low intensity magnetic fields promote phase transitions primarily by altering the structure and mobility of both polymer and solvent. The underlying molecular-scale mechanisms will be investigated via a suite of spectroscopic tools; magneto-rheology and small angle scattering will then determine how these molecular mechanisms manifest at longer lengthscales. Finally, processing parameters such as temperature, field strength, and magnetization geometry will be examined to develop guidelines for precisely controlling the resulting phase and associated mechanical properties. This understanding will then be used to develop guidelines for selecting solvents, BCP architectures, and block chemistries that enhance field-responsiveness, opening an entirely new approach for developing well-ordered BCP materials with finely-tuned properties.

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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.