Laser Surface Thermal Lensing (STL) as a Tool for Probing the Dynamic-Mechanical Properties of Polymer Thin Films: Applications in Detecting Solid-State Phase Transitions, etc.

激光表面热透镜 (STL) 作为探测聚合物薄膜动态机械性能的工具：在检测固态相变等方面的应用。

• 批准号: 9901306
• 负责人: Donald Snyder
• 金额: $ 33.9万
• 依托单位: Eastern Michigan University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9901306&HistoricalAwards=false
• 关键词: Laser; Surface; Thermal; Lensing; STL

9901306SnyderAbsorption of energy from a pulse-modulated laser beam impringing on a transparent material leads to cyclic thermal expansion and contraction of the surface exposed to the beam. This distortion of the surface forms a transient optical lens structure which can be probed by monitoring changes in a second, continuous laser beam reflected at an angle off the lens curvature. Major improvements in detection and quantitation of the reflected probe-beam developed at the EMU Experimental Laser Physics Laboratory have resulted in a highly sensitive technique, termed laser Surface Thermal Lensing (STL), for study of the thermomechanical response of surface materials. Micron-thick films or organic polymers applied over the surface of optical materials have been found to give much stronger STL signals than the glass background. Since the magnitude and phase of the STL signals should be a function of both the absorbtivity and the dynamic/mechanical properties of the polymer, it is reasonable to theorize that any changes in external conditions which affect these properties should result in detectable changes in the STL signal. This research project will study the relationship between laser STL characteristics of a polymer, its structure, mechanical properties and relevant external conditions. Methodology will involve initial study of instrument parameters such as optical bench configuration, pump-beam frequency, power and wavelength in order to optimize the STL response of suitable test polymers. The STL signal behavior will then be studied as a function of temperature for different polymers to determine the feasibility of using this technique to investigate glass-transition and other solid-state phase transitions. The effect of small organic molecules adsorbed from the gas phase into the surface layer of the polymer on the STL response of the polymer film will also be investigated to determine it plasticization effects can be quantified by changes in the STL signal.The laser STL technique has numerous potential applications in polymer structural analysis and related fields since it allows studies of dynamic/mechanical properties for polymers as processed thin films. The ability to measure glass-transition temperatures over minute areas of the polymer surface would be useful in studying structural defects due to phase-separation in commercial coating systems based on polymer blends. The sensors for airborne materials such a solvent vapors and organic pollutants. STL with tuneable infrared lasers could also allow the technique to be used as a sensitive detector for analytical spectroscopy of surface chemical composition.

9901306SNYDERABSRABS吸收能量从脉冲调节的激光束改善透明材料上的激光束会导致循环热膨胀和暴露于光束的表面收缩。表面的这种失真形成了瞬态光晶状体结构，可以通过监测第二个连续的激光束在镜头曲率上反射的连续激光束进行探测。 在EMU实验激光物理实验室开发的反射探针梁的检测和定量的重大改进，导致了一种高度敏感的技术，称为激光表面热透镜（STL），以研究表面材料的热机械响应。 已经发现，在光学材料表面上应用的微米厚膜或有机聚合物比玻璃背景具有更强的STL信号。 由于STL信号的大小和相应是聚合物的吸收率和动态/机械性能的函数，因此合理的理论是，影响这些特性的外部条件的任何变化都应导致STL信号可检测到的变化。 该研究项目将研究聚合物的激光STL特征，其结构，机械性能和相关外部条件之间的关系。 方法学将涉及仪器参数的初步研究，例如光学基准配置，泵梁频率，功率和波长，以优化合适的测试聚合物的STL响应。 然后，将研究STL信号行为作为不同聚合物的温度函数，以确定使用该技术研究玻璃转换和其他固态相变的可行性。 还将研究从气相进入聚合物表面层对聚合物膜的STL响应的影响的影响，还将研究以确定IT在STL信号的变化中可以量化IT塑性效应。激光STL技术具有在聚合物结构分析和相关领域中的众多潜在应用，因为IT允许对Polymers的处理效果进行研究。 由于基于聚合物混合物的商业涂料系统中的相分离，测量聚合物表面微小区域的玻璃转换温度的能力将有助于研究结构缺陷。 空气材料的传感器，例如溶剂蒸气和有机污染物。 具有可调红色激光器的STL还可以使该技术用作表面化学组成分析光谱的敏感检测器。