Structures and growth mechanisms of patterned polycrystals by polarimetric imaging

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The Organic and Macromolecular Chemistry Program in the Chemistry Division at the National Science Foundation supports Professor Bart Kahr at New York University, who will provide an understanding of the structures of polycrystalline formations, which have characteristic lenghtscales of 10 micrometers. The investigator addresses the mechanisms leading to such patterning, the optical properties of the meso-structures, and potential applications in technology and in other scientific fields. Professor Kahr proposes to attack a very complex subject, namely, to use to Mueller matrix imaging polarimetry (and related techniques) to determine the structures and growth mechanisms of banded spherulites of small organic compounds. These polycrystalline systems have been the subject of earlier studies by researchers who proposed a simple, single, growth mechanism that involved the twisting of radii. This proposal attempts to understand growth mechanisms in these self-assembling systems and in some cases reveal new phenomena. Preliminary results suggest that the twisting mechanism is not in fact the universal explanation of optical banding. Future work should lead to a much deeper understanding of the origins of the nonequilibrium pattern formation in these systems. Understanding and controlling the spontaneous formation of chiral mesoscale structures transcend fundamental questions of crystal growth, and may lead to applications from mirrors to waveguides, and in producing chiral thin films.The broader impact of the proposed investigations will be significant. The investigator is dedicated to chemical education starting at the kindergarten level. He has found intriguing evidence that crystallography was one of the topics covered in the curriculum of the first children?s day care facilities in Germany in the 19th century. Professor Kahr has written and translated books and articles on the history of chemistry and crystallography. He is in contact with the authors of major chemistry books to insure that his findings reach undergraduate chemistry students in a timely manner. Courses for teachers are planned and these are major components of the broader outreach plan. The investigator has a track record of working with underrepresented groups of students. Professor Kahr is planning on working with local schools to bring students to his lab to participate in research projects with the hope of developing college-bound scientists who would otherwise never enter the pipeline.