Jones Beatrice E, Wang Zhihang, Zwijnenburg Martijn A, Edwards-Gayle Charlotte J C, Moth-Poulsen Kasper, Cowieson Nathan, Evans Rachel C
Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, Oxfordshire, United Kingdom.
J Am Chem Soc. 2025 Aug 13;147(32):29349-29358. doi: 10.1021/jacs.5c09267. Epub 2025 Aug 3.
Molecular solar thermal energy storage (MOST) materials are a promising method for renewable energy storage that captures solar energy and releases it on demand as heat. Azobenzene is attractive for MOST applications due to its photoreversible isomerization. Recently, phase-change materials have been formed using azobenzene to increase their energy-storage capacity; however, these condensed phases often lower the isomerization degree, which is only recovered on dissolution. In this work, sparing solvent addition is used to drive the self-assembly of azobenzene photosurfactants (AzoPS) into lyotropic liquid crystal (LLC) phases, which are explored for MOST applications for the first time. Using small-angle X-ray scattering (SAXS), polarized optical microscopy, and differential scanning calorimetry (DSC), we show that the structure-isomerization behavior, and energy-storage properties of these light-responsive LLCs can be systematically tuned by adjusting the photosurfactant structure, solvent, and concentration. Furthermore, by developing a method that combines SAXS with DSC, we directly correlate the isomerization-induced LLC phase transitions to their energy-storage contributions. The formation of LLC phases through solvent addition both enhances the degree of isomerization (by up to 20%) and amplifies the structural disordering on isomerization, resulting in energy-storage densities of up to 123 J g. The ability to tune both the structure and isomerization properties in LLC materials suggests significant promise for MOST applications. In addition, the combination of advanced characterization methods used to establish the structure-isomerization-enthalpy (LLC-photoswitch-phase change) relationships provides unique insight into these multicomponent systems and accelerates the design pathways to future iterations for competitive solar energy storage devices.
分子太阳能热能存储（MOST）材料是一种很有前景的可再生能源存储方法，它能捕获太阳能并按需以热的形式释放。偶氮苯因其光可逆异构化而在MOST应用中具有吸引力。最近，已使用偶氮苯形成相变材料以提高其储能能力；然而，这些凝聚相通常会降低异构化程度，而异构化程度仅在溶解时才能恢复。在这项工作中，通过添加少量溶剂来驱动偶氮苯光表面活性剂（AzoPS）自组装成溶致液晶（LLC）相，这是首次对其进行MOST应用探索。通过小角X射线散射（SAXS）、偏振光学显微镜和差示扫描量热法（DSC），我们表明可以通过调节光表面活性剂结构、溶剂和浓度来系统地调整这些光响应性LLC的结构、异构化行为和储能特性。此外，通过开发一种将SAXS与DSC相结合的方法，我们直接将异构化诱导的LLC相变与其储能贡献相关联。通过添加溶剂形成LLC相既提高了异构化程度（高达20%），又放大了异构化时的结构无序性，从而导致储能密度高达123 J/g。在LLC材料中调节结构和异构化特性的能力表明其在MOST应用中具有巨大潜力。此外，用于建立结构 - 异构化 - 焓（LLC - 光开关 - 相变）关系的先进表征方法的结合，为这些多组分系统提供了独特的见解，并加速了未来具有竞争力的太阳能存储设备迭代设计的途径。
