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

这一早期概念探索研究奖助金(EARGER)项目将展示液晶材料一步打印和聚合新工艺的可行性。液晶是棒状的刚性分子，既有类液体(分子的自由扩散)又有类固体(有序分子排列)的性质。液晶弹性体是由长链连接在一起的液晶重复单元制成的橡胶材料，形成真正的固体。已经观察到，当所有液晶单元沿同一方向排列时，加热可以产生300%-400%的材料尺寸变化。这些大的可逆变形对于各种应用非常有用，例如软的、合成的肌肉致动器或可重写的盲文显示器。不幸的是，在将材料形成实际设备通常所需的复杂结构形状时，很难实现对齐。该奖项支持基础研究，以证明在制造过程中对准这些材料的新工艺的可行性。这一新工艺将使定向弹性体材料的3D打印取得进展，这将使生物医学、航空航天、化工和能源行业的新应用成为可能。因此，这项工作将增强美国的经济、社会和全球竞争力。此外，这项研究将通过加强工程教育和在主要是本科院校的本科生参与者中坚持到毕业，直接使STEM劳动力受益。目前制造响应性液晶弹性体的方法依赖于复杂的程序来对准液晶单元，这严重阻碍了这些材料的广泛发展用于实际应用。这项研究的目的是产生一种一步、简便的技术，在材料块中定位液晶部分，同时通过网络交联法固定排列。这种排列将使用液晶和光响应性掺杂剂之间的客体主体相互作用来获得。为了使液晶弹性体具有良好的对准性能，各种反应过程必须同时进行，但时间尺度不同。这项工作的方法将涉及对联合反应动力学的系统探索，以澄清它们在液晶排列中的作用。动力学将用原位红外光谱进行表征。定向弹性体将通过多种技术进行表征，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巨大的，因为它将促进对如何在3D打印等制造过程中原位控制材料各向异性的理解，使广泛的工程师和应用科学家能够设计自适应的、形状可编程的结构和设备。

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.