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、汽车、汽车和整个社会中设备的基础。 材料研究的一个新兴领域是刺激响应材料，这些材料有效地等同于机器，因为它们将能量输入转换为机械输出。 该研究项目的重点是提高保持液晶性的聚合物材料（称为液晶弹性体（LCE））的刺激转导效率。 LCE越来越多地被认为是低材料执行器，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的范式转变。 科学上，这项工作旨在了解聚合物网络中液晶链段的相互作用对这些材料的刺激响应的作用。 值得注意的是，这项研究将通过利用光响应分子作为探针来分离介晶-介晶耦合的温度依赖性。 再加上这方面的努力是一个广泛的推广计划，重点是扩大参与不足的人口在科罗拉多州，课程和推广有关液晶作为一个“被遗忘的状态的物质”，和技术发展的广泛相关的社会利益和国家security.Technical摘要：这项研究活动的目标是实现亚临界相变在完全固体LCE组合物，以锐化和放大这些材料的机械响应。 这项工作的范围是由三个目标：i）调查的贡献，分子间相互作用的介晶成分在LCE的保留paranematic秩序，ii）评估的贡献，非共价，超分子键在LCE中的相变LCE，和iii）利用光致变色部分作为等温和动态探针的临界相行为在LCE。 研究考试将通过系统设计和分子成分和大分子组成的合成，结合稳健的材料表征（成分，结构和机械），采取以材料为中心的方法。 这项研究中开发的新知识将解决LCE中成分和相行为相关性的现有差距，并为未来设计和优化这些材料的响应提供信息。 一个详细的和强大的实验计划，以开发成分-结构-性能的关系，相关的Landau-de Gennes理论的LCEs。 LCE的最新研究利用基于1，4-双[4-（n-丙烯酰氧基丁氧基）苯甲酰氧基]-2-甲基苯介晶核（由三个苯环组成）的二丙烯酸酯单体，其在0.1-1.0%/K范围内表现出应变-温度响应。 向光操纵的顺序将被用来补充这些见解作为一个有区别的方法来动态探测分子间的相互作用和超分子键的保留（或消除）的paranematic顺序的贡献。 这项技术工作与一项更广泛的影响计划相结合，该计划侧重于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有关的先前和当前进展，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NSF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.