Towards Subcritical Phase Transitions in Liquid Crystalline Elastomers

液晶弹性体的亚临界相变

• 批准号: 2105369
• 负责人: Timothy White
• 金额: $ 40万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2105369&HistoricalAwards=false
• 关键词: Towards; Subcritical; Phase; Transitions; Liquid

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.

非技术摘要：液晶材料无处不在：它们是我们家庭、工作场所、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，它实际上相当于机器。他们将能量输入转化为机械输出。该研究项目的重点是提高保留液晶性的聚合物材料（称为液晶弹性体）的刺激传导效率。 （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、健康科学治疗以及有利于国家安全的能力的范式转变。从科学角度来看，这项工作旨在了解液晶相互作用的作用。值得注意的是，这项研究将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。广泛的外展计划，重点是扩大科罗拉多州服务不足人群的参与，与液晶作为“被遗忘的物质状态”相关的课程和外展，以及与社会利益和国家安全广泛相关的技术开发。 技术摘要：目标这项研究活动的目的是在全固态 LCE 组合物中实现亚临界相变，以增强和放大这些材料的机械响应，该工作的范围包括三个目标：i) 研究介晶分子间相互作用的贡献。 ii) 评估 LCE 中非共价超分子键对 LCE 相变的贡献，以及 iii) 利用光致变色部分作为 LCE 研究中关键相行为的等温和动态探针。考试将采用以材料为中心的方法，通过系统设计和合成分子成分和大分子组成，并结合强大的材料表征（成分、结构和机械）新知识。这项研究中开发的方法将解决 LCE 中成分和相行为相关性方面的现有差距，并为这些材料的响应的未来设计和优化提供信息，并提出详细而可靠的实验计划来开发成分-结构-性能关系，与 LCE 的 Landau-de Gennes 理论相关，最近对利用二丙烯酸酯单体的 LCE 进行了研究。 1,4-双[4-(正丙烯酰氧基丁氧基)苯甲酰氧基]-2-甲基苯介晶核（由三个苯环组成），其应变-温度响应范围为0.1-1.0%/K。将用于补充这些见解，作为动态探测分子间相互作用以及超分子键对保留（或消除）的贡献的差异化方法技术工作与更广泛的影响计划相结合，重点是向科罗拉多州服务不足的人群进行宣传，开发展示材料科学和设备工程相互耦合的课堂演示，并建立一个 YouTube 频道来传播相关领域的先前和当前进展。 LCE、研究生培训以及与软机器人工具包的接触，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集成。该奖项反映了 NSF 的法定使命，并被认为值得通过使用软机器人工具包进行评估来支持。基金会的智力价值和更广泛的影响审查标准。

项目成果

Degree of Orientation in Liquid Crystalline Elastomers Defines the Magnitude and Rate of Actuation

• DOI: 10.1021/acsmacrolett.2c00754
• 发表时间: 2023-01-30
• 期刊: ACS MACRO LETTERS
• 影响因子: 7.015
• 作者: Bauman, Grant E.;Hoang, Jonathan D.;White, Timothy J.
• 通讯作者: White, Timothy J.

The Contribution of Oligomerization Reaction Chemistry to the Thermomechanical Properties of Surface-Aligned Liquid Crystalline Elastomers

低聚反应化学对表面取向液晶弹性体热机械性能的贡献

• DOI: 10.1021/acs.macromol.2c02371
• 发表时间: 2023
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: Hebner, Tayler S.;McCracken, Joselle M.;Bowman, Christopher N.;White, Timothy J.
• 通讯作者: White, Timothy J.