Rheology of Lyotropic Nematogenic Nanorod Dispersions

戴维斯0854010该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助。本研究的目的是确定模型溶致纳米柱（例如纳米棒，纳米管，纳米线）分散液的流变行为。 溶致纳米圆柱体分散体的流变学表征仅在最近才通过改进的、更大规模的合成技术和对分散体热力学的更多理解而成为可能。这项研究将确定1）流变学在阐明相行为方面的有效性，2）流变特性对逾渗阈值以上温度的敏感性，以及3）剪切对微观结构的影响。 研究的主要模型系统将是单壁碳纳米管在水溶液中的DNA。 之所以选择这个系统，是因为人们对使用DNA分散纳米管和生产多功能材料越来越感兴趣。 此外，将研究小分子溶剂中的无机纳米柱;无机纳米柱在电子设备、太阳能电池板和传感器中具有重要的应用潜力。这项研究的动机有三个方面。首先，了解纳米柱分散流变学和相行为是液晶科学正在进行的发展的下一步。 基于溶液中棒的相行为的成熟理论，纳米柱分散体应该形成溶致液晶相。然而，具有长的长度，高的纵横比，显着的刚性，和有吸引力的相互作用的纳米圆柱体使它们显着不同于“棒状”聚合物和其他以前研究的系统。 第二，需要建立纳米柱分散体的液晶性的协议。 虽然溶致液晶聚合物溶液的流变特征是众所周知的，但不清楚纳米柱分散体是否会表现出这些相同的特性。第三，人们对自下而上将纳米棒组装成大面积对齐结构的兴趣越来越大。正如了解液晶聚合物的流变学和相行为使先进材料如防弹背心成为可能一样，了解纳米棒分散体的流变学和相行为可能有助于开发从纳米级构建块生产高度对齐的宏观结构的工艺。 这项研究也将有利于未来科学家和工程师的发展。参与这项研究的本科生和研究生研究人员将获得不仅适用于纳米技术，而且适用于雇用训练有素的流变学家的众多领域的经验。研究结果将被纳入PI的“纳米材料的宏观组装”课程，该课程可通过流媒体视频获得。 此外，PI将为参加奥本科学和工程营的中学生开发一个外展模块，并继续努力促进多样性。

Davis0854010This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The objective of this research is to determine the rheological behavior of model lyotropic nanocylinder (e.g. nanorod, nanotube, nanowire) dispersions. Rheological characterization of lyotropic nanocylinder dispersions has only recently been made possible by improved, larger scale, synthesis techniques and increased understanding of dispersion thermodynamics. This research will determine 1) how effective rheology is at elucidating phase behavior, 2) the sensitivity of rheological characteristics to temperature above the percolation threshold, and 3) the effect of shear on microstructure. The primary model system investigated will be single-walled carbon nanotubes in aqueous DNA. This system was chosen because of the growing interest in using DNA to both disperse nanotubes and to produce multifunctional materials. In addition, inorganic nanocylinders in small molecule solvents will be investigated; inorganic nanocylinders have significant potential for use in electronic devices, solar panels, and sensors. The motivation for this research is threefold. First, understanding nanocylinder dispersion rheology and phase behavior is the next step in the ongoing evolution of liquid crystalline science. Based on well-established theories for the phase behavior of rods in solution, nanocylinder dispersions should form lyotropic liquid crystalline phases. However, nanocylinders with long lengths, high aspect ratios, significant rigidities, and attractive interactions make them significantly different than 'rod-like' polymers and other previously investigated systems. Second, protocols are needed for establishing the liquid crystallinity of nanocylinder dispersions. While the rheological signatures of lyotropic liquid crystalline polymer solutions are well known, it is not clear if nanocylinder dispersions will exhibit these same characteristics. Third, there is growing interest in the bottom-up assembly of nanorods into large-area aligned structures. Just as understanding the rheology and phase behavior of liquid crystalline polymers enabled advanced materials such as bullet proof vests, understanding the rheology and phase behavior of nanorod dispersions is likely to facilitate the development of processes for producing highly aligned macroscale structures from nanoscale building blocks. This research will also benefit the development of future scientists and engineers. The undergraduate and graduate student researchers participating in this research will gain experience that is applicable not only to nanotechnology, but also to the numerous fields that employ well-trained rheologists. Research findings will be incorporated into the PI's 'Macroscale Assembly of Nanomaterials' course which is available by streaming video. In addition, the PI will develop an outreach module for middle school students who attend Auburn's science and engineering camps and continue her efforts to facilitate diversity.