Establishing Liquid Crystals of Boron Nitride Nanotubes for Aligned Assemblies

具有更好的取向和性能的坚固和多功能的纳米材料薄膜和纤维的制造使许多应用成为可能，包括热管理材料和防护布。具有长程有序和流动性的纳米材料的溶致液晶被认为是制备具有更好的取向和性能的固体组装体的一种有前途的前体。该奖项支持基础研究，为建立氮化硼纳米管液晶提供框架。氮化硼纳米管是一种轻质纳米材料，具有优异的导热性能，同时还是一种电绝缘体。这些材料性能满足了制造下一代电子和太阳能电池的电绝缘热界面材料以及用于防护纺织品的高强度纤维的关键需求。从电子、能源、航空航天、国防到热包装行业，这种新材料系统的对准组装是一种理想的应用。因此，这项研究的结果将有利于美国的经济和社会。这项研究涉及多个学科，包括制造、液晶科学、纳米技术和工程。这种多学科的方法将同时促进科学发现和广泛包容的、创新的下一代科学和工程工作力量。用于制造定向组件的氮化硼纳米管的液晶尚未实现。本研究旨在填补在有序结构氮化硼纳米管薄膜和纤维的液晶相行为和可控组装方面的知识空白，以提高其性能。纤维素纳米晶体基质是一种可再生的低成本纳米材料，已知可以形成手性向列液晶，它将被用作形成氮化硼纳米管液晶的结构模板。此外，通过与生物聚合物的非共价络合，氮化硼纳米管的稳定的液体分散体也将被实现。这种方法将保留纳米管的固有性质，并在纤维素纳米晶分散体中进一步稳定它们。液晶的相变将通过流变学和光学显微镜进行研究，组装的薄膜和纤维将通过各种成像技术、力学测试和热导率测量进行表征。结合这项研究，这项研究将检验一个广泛的假设，即可以从纤维素纳米晶体模板纳米管系统中获得溶致、手性向列液晶，并且有序的液晶结构可以转化为固体组件以提高性能，从而建立新的纳米材料系统的结构-加工-性能关系。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Manufacturing strong and multifunctional nanomaterial-based films and fibers with improved alignment and properties enables many applications, including thermal management materials and protective fabrics. Lyotropic liquid crystals of nanomaterials with long-range order and fluidity are recognized as a promising precursor to produce solid assemblies with improved alignment and performance. This award supports fundamental research to provide the framework for establishing liquid crystals of boron nitride nanotubes – a lightweight nanomaterial with excellent thermal conductivity while being an electrical insulator. These material properties meet the critical need for manufacturing electrically insulating thermal interface materials for the next generation electronics and solar cells as well as high strength fibers for protective textiles. Aligned assemblies from this new material system are desirable for a wide array of applications from electronics, energy, aerospace, defense, to thermal packaging industries. Therefore, results from this research will benefit the U.S. economy and society. This research involves several disciplines including manufacturing, liquid crystal science, nanotechnology, and engineering. The multidisciplinary approach will simultaneously advance scientific discovery and a broadly inclusive, innovative, next-generation science and engineering workforce.The liquid crystals of boron nitride nanotubes for manufacturing aligned assemblies have not yet been achieved. This research is to fill the knowledge gap on the liquid crystalline phase behavior and the controlled assembly of boron nitride nanotube films and fibers with ordered structures for performance improvement. The cellulose nanocrystal matrix – a renewable and low-cost nanomaterial that is known to form chiral nematic liquid crystals – will be utilized as a structural template for forming liquid crystals of boron nitride nanotubes. Additionally, stable liquid dispersions of boron nitride nanotubes will be achieved by noncovalent complexation with biopolymers. This approach will preserve the intrinsic properties of nanotubes and further stabilize them in cellulose nanocrystal dispersions. The phase transition of liquid crystals will be investigated by rheology and optical microscopy and the assembled films and fibers will be characterized by various imaging techniques, mechanical testing, and thermal conductivity measurements. Combined, this research will test the broad hypothesis that lyotropic, chiral nematic liquid crystals can be obtained from the cellulose nanocrystal-templated nanotube system and the ordered liquid crystalline structures can be translated into solid assemblies for property enhancement, thus establishing the structure-processing-property relationships of the new nanomaterial system.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.