Solvent Permeation, Swelling Profiles and Mechanical Properties of Thin Polymer Films

本研究将研究薄硅氧烷和环氧树脂 聚合物膜将作为线性链被旋转浇铸到 各种衬底（蓝宝石、BK 7玻璃和二氧化硅）， 厚度为50 nm至几微米，然后交联 以形成刚性结构。该研究特别关注 这些薄膜吸收溶剂的机制，以及如何 溶剂的渗透和溶胀影响了 膜与基底的结合，以及膜力学。 溶剂渗透将使用总内标法进行研究。 反射荧光（TIRF），一种技术，其中 将其上粘附有膜的基底放置在 光学棱镜，并且激光束以掠射角撞击 到基底/聚合物膜表面， 指数衰减的倏逝波 通过电影。通过改变入射角， 可以实现穿透深度。使用TIRF，两种类型的 将进行实验。 第一，A的扩散 游离染料进入平衡溶胀膜或部分溶胀膜， 溶胀的膜之后，将发色团放置在膜上， 染料。由倏逝波引起的辐射导致 发色团发出荧光，并通过检测总 作为渗透函数的膜的荧光 深度（通过改变掠射角），染料浓度 可以通过去卷积来计算（参见，当量3）。通过重复 作为时间函数的TIRF角度， 可以构建染料的浓度分布。 在 第二种类型的实验，聚合物网络的一个 未溶胀的膜将被标记。然后电影的正面 暴露于渗透溶剂，并且由于膜溶胀， 对于溶剂吸收，聚合物链将变形， 标签的浓度将变化。 同样，通过利用时间 解决TIRF成角，时间依赖性浓度 可以计算标签的配置文件，并从中了解 膨胀过程中标签的空间分布 可以得到的动态力学响应 膜将被测量，并且显微硬度计将被 用于确定聚合物膜和膜之间的结合， 衬底

This research will study thin siloxane and epoxy polymeric films which will be spin cast as linear chains onto a variety of substrates (sapphire, BK7 glass, and silica) to thicknesses of 50 nm to several microns, and then crosslinked to form a rigid structure. The study focuses specifically on the mechanisms by which these films uptake solvent, and how solvent permeation and swelling affects the adhesion of the film to the substrate, and the membrane mechanics. Solvent permeation will be studied using total internal reflectance fluorescence (TIRF), a technique in which the substrate onto which the film is adhered is placed on an optical prism, and a laser beam impinges at a grazing angle to the substrate /polymer film surface producing an exponentially decaying evanescent wave which penetrates through the film. By varying the angle of incidence, different penetration depths can be achieved. Using TIRF, two types of experiments will be undertaken. In the first, diffusion of a free dye into an equilibrium swollen film or a partially swollen film will be followed by placing a chromophore on the dye. The radiation due to the evanescent wave causes the chromophore to fluoresce, and by detection of the total fluorescence of the film as a function of the penetration depth (by changing the grazing angle), the dye concentration can be computed by deconvolution (cf. eq. 3). By repeating the TIRF angling as a function of time, the time dependent concentration profile of the dye can be constructed. In the second type of experiment, the polymer network of an unswollen film will be tagged. The face of the film will then be exposed to a permeating solvent, and as the film swells due to the solvent uptake, the polymer chains will deform and the concentration of the tag will vary. Again, by using time resolved TIRF angling, the time dependent concentration profile of the labels can be computed, and from these, insight into the spatial distribution of the labels during swelling can be obtained. The dynamical mechanical response of the membrane will be measured, and a microhardness tester will be used to determine the bond between the polymer film and the substrate.