Collaborative Research: Understanding and Controlling the Mechanical and Thermal Properties of Polymer Nanofibers

聚合物在现代文明中无处不在。然而，聚合物通常被认为是不良的导热体，而许多应用将受益于聚合物材料能够作为良好的导热体。最近的研究表明，聚合物材料被显著拉伸后，其机械强度和热传导能力将大大提高。因此，我们的目标是研究在射流中形成的纳米级纤维的机械和热性能。我们预计这些纳米纤维的热传递可能会大大增强，相比较大的，未拉伸的相同聚合物的版本。我们将研究射流如何拉伸聚合物分子，以及由此产生的分子取向如何反过来增强机械强度和热传导，这可能最终导致令人兴奋的新型聚合物材料，这些材料具有极强的强度、柔韧性和良好的导热性。这些材料将实现各种应用，如柔性电子和显示器、太阳能电池和与大功率电子设备集成的先进结构材料，从而导致重大的未来技术进步。该项目将研究和教育组成部分结合起来，在跨学科的环境中培养研究生，并通过范德比尔特大学和菲斯克大学之间的合作，将影响扩大到代表性不足的少数民族。本项目旨在研究电纺聚合物纳米纤维的制造工艺条件、结构以及机械和热性能。该方法是将静电纺丝过程的信息控制、机械和热传输性能测量、全面的微观结构表征和理论分析相结合，以深入了解静电纺丝参数如何影响纳米纤维的微观结构、机械和热性能。结构和性能表征将在单个纳米纤维水平上进行，从而避免平均潜在的纤维非均质性。微观结构将使用微拉曼光谱来表征，这种技术能够从小样本量中提供有关分子组成和取向的详细信息。单个纳米纤维的机械性能将使用原子力显微镜进行三点弯曲测试。单个纳米纤维的热性能将使用定制的微设备进行测量。了解静电纺丝参数如何影响微观结构，以及微观结构与机械/热性能之间的相互作用，我们将能够优化沉积参数，以实现具有可调机械和热性能的聚合物材料。

Polymers find ubiquitous applications in modern civilization. However, polymers are generally regarded as poor heat conductors, while many applications would benefit from polymer materials that are able to function as good heat conductors. Recent studies have suggested polymer materials that have been significantly stretched could have substantially enhanced mechanical strength and heat conduction. We therefore aim to study the mechanical and thermal properties of nanoscale fibers formed in a jet that induces significant stretching. We expect that heat transport in these nanofibers may be profoundly enhanced compared to larger, unstretched versions of the same polymer. We will study how the jet stretches the polymer molecules, and how the resulting molecular orientation in turn results in enhanced mechanical strength and heat conduction, which may eventually lead to exciting new polymer materials that are extremely strong, flexible, and good conductors of heat. Such materials would enable a variety of applications, such as flexible electronics and displays, solar cells, and advanced structural materials integrated with high-power electronics, leading to significant future technological advancements. The project has integrated research and educational components to train graduate students in an interdisciplinary environment, and to extend the impact to underrepresented minorities through collaboration between Vanderbilt and Fisk universities.This project aims to correlate the manufacturing process conditions, structure, as well as mechanical and thermal properties of electrospun polymer nanofibers. The approach is to integrate informed control of the electrospinning process, mechanical and thermal transport property measurement, thorough microstructural characterization, and theoretical analysis to achieve an in-depth understanding of how electrospinning parameters affect nanofiber microstructure, mechanical and thermal properties. The structure and property characterization will be performed at an individual nanofiber level, thereby avoiding averaging over potential fiber heterogeneity. Microstructure will be characterized using micro-Raman spectroscopy, a technique which is able to provide detailed information about molecular composition and orientation from a small sample volume. Mechanical properties of individual nanofibers will be characterized using an atomic force microscope to perform a 3-point bend test. Thermal properties of individual nanofibers will be measured using custom-built microdevices. With an understanding of how electrospinning parameters affect microstructure, and the interplay between microstructure and mechanical/thermal properties, we will be able to optimize deposition parameters to achieve polymeric materials with tunable mechanical and thermal properties.