Towards Subcritical Phase Transitions in Liquid Crystalline Elastomers

非技术总结：液晶材料无处不在：它们是我们家庭、工作空间、汽车和整个社会设备的基础。材料研究的一个新兴领域是刺激响应材料，它有效地等同于机器，因为它们将能量的输入转化为机械输出。本研究项目的重点是提高保持液晶性的聚合物材料的刺激转导效率，这种材料被称为液晶弹性体（LCEs）。lce越来越被认为是一种低材料致动器，可以实现机器人技术、健康科学疗法和有利于国家安全的能力方面的范式转变。从科学的角度来看，这项工作旨在了解聚合物网络中液晶段的相互作用对这些材料的刺激反应的作用。值得注意的是，本研究将利用光响应分子作为探针分离介质-介质耦合的温度依赖性。与这一努力相结合的是一项广泛的外展计划，重点是扩大科罗拉多州服务不足人口的参与，与液晶作为“被遗忘的物质状态”有关的课程和外展，以及与社会利益和国家安全广泛相关的技术开发。技术概述：这项研究活动的目标是在全固态LCE组合物中实现亚临界相变，以提高和放大这些材料的机械响应。这项工作的范围有三个目标：1)研究LCE中介生成分的分子间相互作用对副势序保持的贡献；2)评估LCE中非共价键、超分子键对LCE相变的贡献；3)利用光致变色基团作为LCE中临界相行为的等温和动态探针。研究考试将采取以材料为中心的方法，通过系统的设计和合成分子成分和大分子成分，以及强大的材料表征（成分、结构和机械）。本研究中开发的新知识将解决LCEs中成分和相行为相关性的现有空白，并为这些材料的响应的未来设计和优化提供信息。提出了一个详细而稳健的实验计划，以发展与LCEs的朗多-德-热纳理论相关的成分-结构-性质关系。LCE的最新研究使用了基于1,4-双[4-（n-丙烯氧基丁氧基）苯甲酰氧基]-2-甲苯介晶核（由三个苯基环组成）的二丙烯酸酯单体，其应变温度响应范围为0.1-1.0%/K。对有序的趋光性操纵将作为一种差异化的方法来补充这些见解，以动态地探测分子间相互作用和超分子键对保持（或消除）超分子有序的贡献。这项技术努力与一项更广泛的影响计划相结合，该计划的重点是向科罗拉多州服务不足的人群提供服务，开发展示材料科学和设备工程相互耦合的课堂演示，建立一个YouTube频道，传播与lce相关的过去和当前进展，研究生培训，并参与软机器人工具包，以促进对这些材料进行必要的技术评估，并促进机器人技术的整合。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 SUMMARY:Liquid crystalline materials are pervasive: they are the basis of devices in our homes, workspaces, automobiles, and throughout society. An emerging area of materials research are stimuli-responsive materials that are effectively equivalent to machines in that they convert an input of energy into a mechanical output. This research project is focused on enhancing the efficiency of stimuli-transduction of polymeric materials that retain liquid crystallinity, which are called liquid crystalline elastomers (LCEs). LCEs are increasingly considered as low material actuators that could enable paradigm-shifting advances in robotics, therapies in health sciences, and capabilities that benefit national security. Scientifically, this effort seeks to understand the role of the interaction of the liquid crystalline segments in polymer networks to the stimuli-response of these materials. Notably, this research will isolate the temperature dependence of mesogen-mesogen coupling by utilizing light-responsive molecules as a probe. Coupled to this effort is an extensive outreach plan focused on broadening participation in underserved populations in the state of Colorado, curriculum and outreach relating to liquid crystals as a “Forgotten State of Matter”, and technology development of broad relevance to societal interests and national security.TECHNICAL SUMMARY:The goal of this research activity is to realize subcritical phase transitions in fully solid LCE compositions to sharpen and amplify the mechanical response of these materials. The effort is scoped by three objectives: i) investigate the contribution of intermolecular interaction of mesogenic constituents in LCEs to the retention of paranematic order, ii) assess the contribution of non-covalent, supramolecular bonds in LCE to phase transitions in LCE, and iii) exploit photochromic moieties as an isothermal and dynamic probe of critical phase behavior in LCEs. The research examination will undertake a materials-centric approach via systematic design and synthesis of both the molecular constituents and macromolecular composition coupled to robust materials characterization (compositional, structural, and mechanical). The new knowledge developed in this research will address existing gaps in the correlation of composition and phase behavior in LCEs as well as inform future design and optimization of the response of these materials. A detailed and robust experimental plan is presented to develop composition-structure-property relationships, correlated to the Landau-de Gennes theory of LCEs. Most recent research examinations of LCE utilize diacrylate monomers based on the 1,4-Bis[4-(n-acryloyloxybutyloxy)benzoyloxy]-2-methylbenzene mesogenic core (composed of three phenyl rings), which exhibit strain-temperature response in the range of 0.1-1.0%/K. Phototropic manipulation of order will be used to complement these insights as a differentiated approach to dynamically probe the intermolecular interactions and the contribution of supramolecular bonds to the retention (or elimination) of paranematic order. The technical effort is integrated with a broader impact plan focused on outreach to underserved populations in the state of Colorado, development of classroom demonstrations showcasing the intercoupling of materials science and device engineering, a YouTube channel to disseminate prior and current advances relating to LCEs, graduate student training, and engagement with the Soft Robotics Toolkit to facilitate necessary technological assessment of these materials and facilitate integration in robotics. .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.