Collaborative Research: Understanding Cholesteric Pitch in Nanocylinder Films

合作研究：了解纳米圆柱薄膜中的胆甾醇沥青

• 批准号: 1437073
• 负责人: Micah Green
• 金额: $ 19.07万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1437073&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Cholesteric; Pitch

CBET 1436637/1437073Liquid crystals are material phases that exhibit both crystalline order and the fluidity of a liquid. This project will investigate the properties of nanocylinder dispersions that can form liquid crystals. The particular liquid crystals being investigated are termed cholesteric (chiral) because the nanocylinders align in a preferred direction, but the preferred direction itself rotates about an axis. As a result of this structure, cholesteric liquid crystals can have unusual optical properties. When the materials are processed into thin films, the unusual structure and optical properties are maintained, which makes the materials especially interesting for applications such as liquid crystal displays, decorative coatings, and specialty inks. This project will investigate the rheological properties of nanocylinder dispersions and analyze how flow changes the microstructural characteristics and optical properties of the materials when processed into thin films. The results will help scientists and engineers to design and process cholesteric liquid crystals into films with controlled optical properties.A combination of experiments and modeling will be used to understand the effects of dispersion properties and flow on dispersion rheological and morphological properties. This will result in parameter space maps for the dispersion rheology and microstructure as a function of composition and shear rate. Two model systems capable of forming lyotropic cholesteric liquid crystals will be investigated: aqueous dispersions of sulfonated cellulose nanocrystals and aqueous dispersions of double stranded DNA and single-walled carbon nanotubes. For both systems, a combination of mesoscopic polydomain modeling techniques and physical experiments will be used to investigate the following features: 1) the microstructure (texture) as a function of mesogen concentration as probed by oscillatory rheology, 2) transients during the start-up of steady shear, 3) the steady shear rheological behavior, particularly at low shear, 4) texture at rest and texture development after flow cessation, and 5) texture and optical properties of solidified films.

CBET 1436637/1437073液晶是表现出晶体有序性和液体流动性的物质相。本项目将研究可形成液晶的纳米柱分散体的性质。正在研究的特定液晶被称为手性（手性），因为纳米柱在优选方向上排列，但优选方向本身绕轴旋转。由于这种结构，液晶可以具有不寻常的光学特性。当材料被加工成薄膜时，保持了不寻常的结构和光学特性，这使得材料在液晶显示器，装饰涂料和特种油墨等应用中特别有趣。该项目将研究纳米圆柱分散体的流变特性，并分析流动如何改变材料加工成薄膜时的微观结构特征和光学特性。研究结果将有助于科学家和工程师设计和加工具有可控光学性能的液晶薄膜，并将实验和模型相结合来了解分散体性质和流动对分散体流变学和形态学性质的影响。这将导致作为组成和剪切速率的函数的分散体流变学和微观结构的参数空间图。两个模型系统能够形成溶致液晶将被调查：水分散液的磺化纤维素纳米晶体和水分散液的双链DNA和单壁碳纳米管。对于这两个系统，将使用介观多域建模技术和物理实验的组合来研究以下特征：1）通过振荡流变学探测的作为介晶浓度的函数的微观结构（织构），2）稳态剪切启动期间的瞬变，3）稳态剪切流变行为，特别是在低剪切下，4）静止织构和流动停止后织构的发展; 5）凝固膜的织构和光学性质。