STRUCTURAL ORIGINS IN PHOTOSWITCHABLE ORGANIC FERROELECTRICITY USING TIME-RES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Organic ferroelectric materials are important for applications of information storage, molecular motors and actuators. The advantages of organic ferroelectric materials over their inorganic counter part are their chemical tunability, processibility and self-repair capability. Therefore, understanding the structural origins in organic ferroelectric materials and their connections to the properties of the materials is crucial in developing new materials with broad applications. The proposed work will investigate the structural origins of a group of photo-switchable organic ferroelectric materials made of small aromatic organic electron donors (D) and acceptors (A) self-assembled into alternating three dimensional DADA? arrays by steady-state and time-resolved x-ray diffraction techniques at Beamline 14ID of the APS. The structural origins for such photoswitchable ferroelectric materials are structural changes either due to change of the DA distances or rotation of the side groups that form or disrupt the hydrogen bonds. Using TR-XRD, Collet, Techert, et al. carried out pioneering studies on similar type of materials with power diffraction at ESRF. We are encouraged by their success and believe that our materials can be studied by the TR-XRD with Laue diffraction on single crystals at Beanline 14ID. We would like to capture the structural origins that enable the ferroelectricity and distinguish different types of the structural changes. The proposed structural studies will be combined with single crystal ultrafast transient absorption and emission spectroscopy conducted in our labs in Northwestern University. The structural information obtained at the APS and spectroscopic and theoretical as well as chemical synthesis will enable a productive interdisciplinary research to discover, character, and applying new materials.