CAREER: Internal Structure and Properties of Confined Layer-by-Layer Films and Nanotubes

技术概述：逐层(LBL)组装代表了一种新颖的革命性材料类别，其潜在应用范围从生物和能源系统到智能表面和传感器。然而，它们的内部结构和材料性能很难识别，因为它们往往超薄或仅限于其衬底。正如许多中性聚合物所显示的那样，随着薄膜厚度的减小，材料的性能(如玻璃化转变温度)与本体行为显著不同。这项工作的目的是(I)使用量热法、椭偏仪和电化学来识别不同厚度、曲率(以聚合物纳米管的形式)的LBL组件和组件中的物理和结构差异，以及(Ii)将这些信息与LBL薄膜的生长和性能联系起来。块状自支撑LBL薄膜将与涂覆LBL的多孔模板进行比较。LBL厚度和孔直径将分别改变，以隔离限制和曲率的影响。对于不同pH和离子强度的聚电解质溶液，也将探索聚电解质在小孔内的组装和吸附。将比较含有纳米颗粒和不含纳米颗粒的复合LBL薄膜的层结构和性能，以确定某些层中硬无机材料的影响。量热法将获得热波动，椭偏仪将获得与薄膜内相变相关的密度波动。电化学渗透率测量将使用氧化还原活性探针定性地确定薄膜内的结构和自由体积。总而言之，这些技术将为LBL组件提供关于层混合、聚电解质络合和限制的新知识。非技术摘要：逐层(LBL)组件代表着一种令人兴奋的新类别的聚合物涂层和薄膜。由相反电荷分子的交替层制成的LBL薄膜在能量存储和生产、生物材料、自清洁表面等方面有应用。然而，关于这些薄膜在特定温度下是熔化、软化还是交联，人们知之甚少；如果LBL组装要商业化，这些知识对于识别这些知识是重要的。在这个项目中，我们将测定LBL薄膜和LBL纳米管的热学性质。其目的是了解厚度、曲率和成分如何影响薄膜的结构和性能。如果成功，所获得的知识可以用于操纵和设计用于有机能量存储和其他应用的薄膜。该计划的主要影响将是获得新的知识和对STEM学科中的个人进行指导。参与者将学习最先进的人物刻画和处理技术以及宝贵的专业技能。一名研究生将得到资助。计划通过在线视频演示、德克萨斯农工大学高中教师S E3项目、德克萨斯农工大学S面向年轻女性的女性探索工程项目等渠道开展社区推广活动。

TECHNICAL SUMMARY: Layer-by-layer (LbL) assemblies represent a novel and revolutionary class of materials with potential applications ranging from biological and energy systems to smart surfaces and sensors. However, their internal structure and materials properties are challenging to discern because they are often ultra thin or confined to their substrate. As shown for many neutral polymers, the materials properties (such as the glass transition temperature) significantly depart from bulk behavior as the film thickness deceases. The aim of this work is (i) to discern physical and structural differences within LbL assemblies of varying thickness, curvature (in the form of polymer nanotubes), and components using calorimetry, ellipsometry, and electrochemistry and (ii) to relate that information to how LbL films grow and perform. Bulk free-standing LbL films will be compared to LbL-coated porous templates. LbL thickness and pore diameter will be varied to isolate the influence of confinement and curvature, respectively. The assembly and adsorption of polyelectrolytes within small pores will also be explored for polyelectrolyte solutions of varying pH and ionic strength. Layer-structure and properties of composite LbL films containing nanoparticles will be compared to those without to determine the influence of hard inorganic materials within some of the layers. Calorimetry will access thermal fluctuations and ellipsometry will access density fluctuations related to phase transitions within the film. Electrochemical permeability measurements will qualitatively determine structure and free volume within the films using redox-active probes. Together, these techniques will give new knowledge regarding layer mixing, polyelectrolyte complexation, and confinement for LbL assemblies.NON-TECHNICAL SUMMARY: Layer-by-layer (LbL) assemblies represent an exciting new class of polymer coatings and films. Made from the alternating layers of oppositely charged molecules, LbL films have applications in energy storage and production, biomaterials, self-cleaning surfaces, and more. However, little is known regarding whether these films melt, soften, or crosslink at a given temperature; such knowledge is important to discern if LbL assemblies are to be commercialized. In this program, the thermal properties of LbL films and LbL nanotubes will be determined. The aim is to understand how thickness, curvature, and components influence film structure and properties. If successful, acquired knowledge could be used to manipulate and design thin films for organic energy storage and other applications. The major impact of this program would be in the acquisition of new knowledge and mentoring of individuals in STEM disciplines. Participants will learn state-of-the-art characterization and processing techniques as well as valuable professional skills. One graduate student will be supported. Community outreach is planned via online video demonstrations, Texas A&M University?s E3 program for high school teachers, Texas A&M University?s Women Explore Engineering program for young women, and other outlets.