In-Situ Optical Monitoring for Langmuir/Blodgett Deposition

为创造工程聚合物超薄膜系统(PUF)制定设计和制造方案的机会很可能取决于复杂的现场诊断技术的发展。朗缪尔/布洛杰特沉积技术为有机物在光学计算、电子和生物技术等重要新兴领域的应用奠定了基础。这些应用依赖于对材料性质的精确控制，例如活性部分的位置和取向顺序、层的交替和厚度。随着需要研究沉积的聚合物混合物和化合物以创建具有三维有序的薄膜系统，显然需要开发能够跟踪单分子层从空气/水界面提取时的弹性动力学、流体动力学和电动力学行为的方法。在这个项目中，建议在接触线以及上下休息处引入激光。二次谐波产生(SHG)是一种很有前途的探测手段，它被用来研究分子在朗缪尔层上的取向，以及表征光学高度非线性染料的完整膜系的有序性。通过比较来自朗缪尔层的倍频与在衬底上的水接触线以及后来在上部静止(干燥)位置获得的倍频，PI能够通过极化旋转测量染料部分的重定向，通过幅度变化测量面积/分子的变化，以及通过检查这些对不同分子和衬底的相同影响来测量化学降解和干燥。在最初的工作中，PI计划尝试确认这样的测量是可能的，并且动态发生在时间尺度上，这验证了进一步研究的必要性。如果这种动态变化是明显的，准确的监测可能允许微妙地调整槽条件，以改善胶片质量。这些测量将提供目前无法获得的关于早期单层和后续层之间的行为差异的有价值的信息。当朗缪尔层转变为特定沉积的单分子膜时，光返回信号将有助于建立朗缪尔层的转变历史。如果这项工作成功，它将为更多的光学和红外光谱仪开辟道路，能够检测薄液膜中构象和成键的细微变化。

The opportunity to create design and manufacturing protocols for the creation of engineered polymeric ultrathin film systems (PUFS) may well rest on the development of sophisticated, in-situ diagnostics. The Langmuir/Blodgett deposition technique offers the possibility of providing the foundation for the application of organics to important emerging fields, such as optical computing, electronics, and biotechnology. These applications depend on precise control of materials properties such as positional and orientational order of active moieties, alternation of layers, and thickness. With the need to investigate mixtures and compounds of polymers being deposited in order to create film systems possessing three-dimensional order, it has become evident that methods need to be developed capable of tracking the elastodynamic, hydrodynamic, and electrodynamic behavior of the monolayers as they are extracted from the air/water interface. It is proposed in this project to introduce laser beams at the contact line, as well as at the upper and lower resting positions. Second harmonic generation (SHG), which appears to be a very promising probe, is used here to study the orientation of molecules on the Langmuir layer, as well as to characterize the order of completed film systems of optically highly nonlinear dyes. By comparing the SHG from the Langmuir layer with that obtained at the water contact line on the substrate, and later at the upper resting (drying) position, the PI's are able to measure reorientation of the dye moiety through polarization rotation, changes in area/molecule through amplitude changes, and chemical degradation and drying by examining these same effects on different molecules and substrates. In this initial effort, the PI's plan to attempt to confirm that such measurements are possible, and that dynamics are occurring during time scales which validate the need to pursue further study. If such dynamical changes are evident, accurate monitoring may allow delicate adjustment of trough conditions for improved film quality. These measurements will provide valuable information not presently available concerning the distinctions between the behavior of the early monolayers and that of subsequent layers. The optical return signal will aid in establishing the transitional history of the Langmuir layer as it is transformed into a specific deposited monolayer. If this work is successful, it will open the way to additional optical and infrared spectroscopies capable of detecting subtle changes in conformation and bonding in thin liquid films.