Understanding How Reaction Kinetics and Morphology Affect Photomechanical Molecular Crystals

摘要：在这个由材料研究部固态与材料化学项目资助的项目中，加州大学河滨分校的Christopher Bardeen教授正在使用新的化学方法和表征技术相结合，使有机晶体更接近实际应用。由光敏分子组成的有机晶体可以经历各种光诱导的形状变化，如弯曲、扭曲和卷曲。这些材料可以应用于从工程到医学到细胞生物学的广泛领域，因为它们可以制造出由光驱动的微型设备。这种装置的一个例子是用于显微手术或药物输送的光动力游泳器。这些光电材料的应用受到对其工作原理和如何优化其性能的有限理解的阻碍。PI将通过控制分子结构和晶体形状等重要参数来解决这些挑战，同时设计新的光学实验来研究光诱导的变化如何在晶体内部发生。技术摘要：创造稳定的光反应分子是获得性能更好的材料的先决条件。研究的一个阶段集中在制造新的分子，以制造可以在空气和溶剂中存活的晶体结构。例如，氟取代的使用将提高分子氧化电位，也可能增强晶体塑性。分子晶体还可以表现出非线性时空反应动力学，从而导致自催化、增强的机械响应和稳态照明下的振荡运动。振荡运动可以潜在地利用为微型游泳者提供运动。随着新的理论方法的发展，一种新的驻波荧光实验将直接探测单晶中的非线性反应动力学。最后，自下而上的溶液生长和自上而下的激光切割将用于创建具有明确方向和形状的晶体。通过控制晶体形状和相对于该形状的应变张量的方向，对这两个变量如何决定晶体对光的响应的详细研究将成为可能。这项工作的更广泛的影响包括由将光子转化为机械运动并启用新设备的新材料产生的潜在社会影响。参与的研究生和本科生将接受光谱学、材料表征和数据分析方面的培训，这将使他们能够在光子学等重要的经济领域做出贡献。PI还将继续在塔夫脱小学开展正在进行的外展工作，每年影响数百名未被充分代表的少数民族学生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical Abstract:In this project funded by the Solid-State and Materials Chemistry Program of the Division of Materials Research, Professor Christopher Bardeen of the University of California, Riverside is using a combination of novel chemical methods and characterization techniques to take organic crystals closer to practical applications. Organic crystals composed of light-sensitive molecules can undergo a variety of light-induced shape changes such as bending, twisting, and coiling. These materials could have application across a broad range of fields spanning from engineering to medicine to cell biology, by making it possible to create microdevices powered by light. One example of such a device would be a light-powered swimmer for microsurgery or drug delivery. The application of these photomechanical materials is hampered by a limited understanding of how they work and how their performance can be optimized. The PI will address these challenges by controlling important parameters like molecular structure and crystal shape, while designing new optical experiments to examine how the light-induced changes occur inside the crystals. Technical Abstract:The creation of stable photoreactive molecules is a prerequisite for better performing materials. One phase of the research concentrates on making new molecules to make crystalline structures that can survive exposure to air and solvents. For example, the use of fluorine substitution will raise the molecular oxidation potential and may also enhance crystal plasticity. Molecular crystals can also exhibit nonlinear spatio-temporal reaction kinetics that can lead to autocatalysis, enhanced mechanical response, and oscillatory motion under steady-state illumination. Oscillatory motion can potentially be harnessed to provide locomotion for micro-swimmers. Along with new theoretical approaches, a novel standing-wave fluorescence experiment will be developed to directly probe the nonlinear reaction kinetics in single crystals. Finally, both bottom-up solution growth and top-down laser cutting will be used to create crystals with well-defined orientations and shapes. By controlling both crystal shape and the orientation of the strain tensor with respect to that shape, a detailed investigation into how both variables determine the crystal's response to light will become possible. The broader impacts of this work include potential societal impacts resulting from new materials that transform photons into mechanical motion and enable new devices. Participating graduate and undergraduate students will receive training in spectroscopy, materials characterization, and data analysis that will enable them to contribute in economically important areas like photonics. The PI will also continue ongoing outreach efforts at Taft Elementary School that impact hundreds of underrepresented minority students each year.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.