Molecular Layers under Control

这项研究的目的是探索一种新的概念，利用基于液晶(LC)的墨水和图案化锚定排列印章相结合的方法来制备具有工程分子尺度的组织和组成的多组分有机薄膜。中心思想是通过竞争性LC锚定在邮票和SAM表面产生的弹性应变场，将向列相墨水沉积的多组分自组装单分子层(SAM)中的分子有序和组成耦合到邮票上的图案。这一概念类似于固-固界面上的应变异质外延生长，不同之处在于应变场是由向列相液晶而不是衬底提供的，并且是由锚定和弹性力而不是外延失配造成的。尽管液晶的弹性常数比大多数固体要弱得多，但通过选择具有适当能量平衡的系统，我们展示了液晶如何仍然具有显著的影响，同时在结构和组成控制方面提供了相当大的灵活性。这项研究的动机既有根本的利益，也有开发替代方法来创建具有纳米到微米长度的设计者结构的化学功能化表面的实际重要性。除了加深我们对有机薄膜中液晶-表面相互作用、相行为和图案形成的基本理解外，这项工作中将要开发的技术代表着朝着制备具有定制的物理和化学性质的材料的方向迈进了一步，该材料具有潜在的应用，从受控的润湿和粘合到化学传感和液晶显示技术。我们提议研究的概念代表了一种从分子水平利用宏观影响来驾驭和控制自组装的全新方法，借鉴了液晶科学和多相系统的思想。为了开展这项工作，LCD和LC-表面相互作用的访问学者和专家David Patrick教授与多相系统和有机薄膜物理化学专家Stuart Clarke博士建议进行跨学科合作。西华盛顿大学化学教授兼先进材料科学与工程中心主任Patrick博士是热致液晶溶剂制备有序材料非传统用途的先驱，而剑桥大学的Clarke博士团队则专门研究多组分和多相体系的分子尺度性质。这项合作将把这两个研究领域结合起来。在剑桥期间，访问学者将与化学系和BP研究所的其他小组以及英国其他几所大学的小组进行互动，他们将从他带来的这些新颖方法的专业知识中受益。从长远来看，这项拟议的研究将为帕特里克回国后继续进行的持续合作奠定基础。拟议的实验计划将产生一幅关于薄膜成分与结构特性、液晶力以及使用液晶墨水沉积的自组装单分子膜中单分子层形成热力学之间关系的综合图景。虽然人们对表面对LCS的影响给予了很大的关注，包括用SAM装饰的表面，但很少考虑相反的情况，即LCS对LCS的影响。综上所述，这些实验的结果应该会对基于液晶的油墨的可行性提供明确的评估，同时加深我们对科学上有趣的和技术上重要的潜在现象的理解。

The goal of the proposed research is to investigate a new concept for preparing multi-component organic thin films with engineered molecular-scale organization and composition using liquid crystal (LC)-based inks combined with patterned anchoring alignment stamps. The central idea is to couple molecular order and composition in a multicomponent self-assembled monolayer (SAM) deposited from a nematic ink to a pattern on a stamp through an elastic strain field produced by competitive LC anchoring at the stamp- and SAM surfaces. The concept resembles strained heteroepitaxial growth at a solid-solid interface, except that the strain field is provided by a nematic LC, rather than the substrate, and results from anchoring and elastic forces, rather than an epitaxial mismatch. Despite the fact that LC elastic constants are much weaker than those of most solids, by selecting systems with an appropriate balance of energies we show how the LC can nevertheless have a significant influence, while affording considerable flexibility in structural and compositional control.The research is motivated by both fundamental interests and the practical importance of developing alternative approaches for creating chemically functionalized surfaces with designer architectures at nanometre to micron length scales. In addition to furthering our basic understanding of LC-surface interactions, phase behaviour, and pattern formation in organic thin films, the techniques to be developed in this work represent a step toward preparing materials with tailored physical and chemical properties, potentially useful for applications ranging from controlled wetting and adhesion, to chemical sensing and LC display technology.The concepts we propose to investigate represent a fundamentally new approach for using macroscopic influences to harness and control self-assembly at the molecular-scale, drawing upon ideas from LC science and multiphase systems. To carry out the work, an interdisciplinary collaboration is proposed between Prof. David Patrick, the Visiting Fellow and expert in LCs and LC-surface interactions, and Dr. Stuart Clarke, an expert in multiphase systems and the physical chemistry of organic thin films. Dr. Patrick, who is a Professor of Chemistry and Director of the Advanced Materials Science and Engineering Centre at Western Washington University, is a pioneer in unconventional uses of thermotropic LC solvents to prepare organized materials, while Clarke's group at Cambridge specialises in the molecular-scale properties of multi-component and multi-phase systems. The collaboration will combine these two areas of study.While at Cambridge, the Visiting Fellow will interact with other groups in the Chemistry Department and BP Institute, as well as those at several other universities across the UK, who will benefit from the expertise he brings in these novel approaches. Longer term, the proposed research will lay the foundations for a sustained collaboration that can continue after Patrick returns to his home institution.The proposed experimental programme would produce a comprehensive picture of the relationships between film composition and structural properties, LC forces, and the thermodynamics of monolayer formation in self-assembled monolayers deposited using LC inks. Although great deal of attention has been given to understanding the influence surfaces exert on LCs, including surfaces decorated with SAMs, the reverse situation-that is, LCs influencing surfaces-has hardly been considered at all. Taken together, the results of these experiments should provide a definitive assessment of the feasibility of LC-based inks, while deepening our understanding of the scientifically interesting and technologically important underlying phenomena.