EAGER/RUI: One-Step, Programed Alignment of Liquid Crystal Elastomers by Guest Host Interactions

这个早期概念探索性研究资助（EAGER）项目将证明一种新型的液晶材料一步印刷和聚合工艺的可行性。液晶是棒状的刚性分子，具有液体状（分子的自由扩散）和固体状（有序分子排列）的性质。液晶弹性体是由液晶重复单元以长链连接在一起形成真正的固体制成的橡胶材料。已经观察到，当所有液晶单元在相同方向上排列时，通过加热可以产生300- 400%的材料尺寸变化。这些大的、可逆的变形对于诸如软的、合成肌肉致动器或可重写盲文显示器的各种应用可能是非常有用的。不幸的是，在将材料形成为实际装置通常所需的复杂结构形状时，难以实现对准。该奖项支持基础研究，以证明在制造过程中对齐这些材料的新工艺的可行性。这一新工艺将推动对齐弹性体材料的3D打印，从而为生物医学、航空航天、化学和能源行业的新应用提供支持。因此，这项工作将提高美国经济、社会和全球竞争力。此外，这项研究将直接受益于STEM劳动力，通过提高工程教育和坚持毕业的本科参与者在一个主要的本科院校。目前的方法来制造响应液晶弹性体依赖于精心制作的程序，以调整液晶单元，代表了一个严重的障碍，这些材料的广泛发展的实际应用。本研究的目的是产生一个一步，简便的技术，定向液晶部分的材料散装，同时通过网络交联固定的对齐。将使用液晶和光响应掺杂剂之间的宾主相互作用来获得对准。 为了产生液晶弹性体的稳健配向，各种反应过程必须同时进行，但具有不同的时间尺度。这项工作的方法将涉及一个系统的探索相结合的反应动力学，以澄清它们在液晶取向的作用。将通过原位红外光谱表征动力学。对齐的弹性体将通过几种技术来表征，包括偏振紫外-可见光谱、差示扫描量热法和动态力学分析。这项研究对更广泛的知识体系的贡献将是重要的，因为它将促进人们对材料各向异性如何在3D打印等制造过程中原位控制的理解，从而使广泛的工程师和应用科学家能够设计自适应的形状可编程结构和设备。

This EArly-concept Grant for Exploratory Research (EAGER) project will demonstrate feasibility for a novel one-step printing and polymerization process for liquid crystal material. Liquid crystals are rod-like, rigid molecules that have both liquid-like (free diffusion of molecules) and solid-like properties (ordered molecular arrangements). Liquid crystal elastomers are rubbery materials made from liquid crystal repeat units connected together in long chains forming a true solid. It has been observed that when all the liquid crystal units line up in the same direction that material size changes of 300-400 percent can be produced by heating. These large, reversible deformations could be extremely useful for a variety of applications such as soft, synthetic muscle actuators or rewriteable braille displays. Unfortunately, alignment is difficult to attain while forming the material into the complex structural shapes typically required for practical devices. This award supports fundamental research to demonstrate the feasibility of a new process for aligning these materials during manufacture. This new process will enable advancement toward 3D printing of aligned elastomer materials which will empower new applications in the biomedical, aerospace, chemical, and energy industries. As a result, this work will enhance the U.S. economy, society, and global competitiveness. Additionally, this research will directly benefit the STEM workforce by enhancing engineering education and persistence to graduation among undergraduate participants at a primarily undergraduate institution.Current approaches to fabricating responsive liquid crystal elastomers rely on elaborate procedures to align the liquid crystal units that represent a serious impediment to the widespread development of these materials for practical applications. The objective of this research is to generate a one-step, facile technique for orienting liquid crystal moieties in the material bulk while simultaneously fixing the alignment through network cross-linking. The alignment will be obtained using guest host interactions between the liquid crystals and photo-responsive dopants. To produce robust alignment of the liquid crystal elastomer the various reaction processes must proceed simultaneously, but with distinct time scales. The approach for this work will involve a systematic exploration of the combined reaction kinetics in order to clarify their role in liquid crystal alignment. Kinetics will be characterized by in situ infrared spectroscopy. Aligned elastomers will be characterized by several techniques including, polarized ultraviolet-visible spectroscopy, differential scanning calorimetry, and dynamic mechanical analysis. The contribution of this research to the greater body of knowledge will be significant because it will advance understanding of how material anisotropies can be controlled in situ during manufacturing processes such as 3D printing, enabling the design of adaptive, shape-programmable structures and devices by a broad range of engineers and applied scientists.