Fourier-transform infrared (FTIR) spectroscopy is a common tool for determining, both qualitatively and quantitatively, the chemical composition of a material in the solid, liquid, or gas phase. It is additionally used as a technique to monitor the rate of chemical changes. These chemical changes can have rheological relevance, e.g., polymerization kinetics, rubber crosslinking, or epoxy curing, just to mention a few. We report the design of an IR transparent upper-plate rheological geometry used as an attenuated total reflectance (ATR) sampling tool. Additionally, we describe the technical and methodological adaption of the ATR crystal into an ARES G2 rheometer for combined FTIR and rheological measurements. In this new setup, a strain-controlled rheometer is combined with an ATR crystal and the IR beam is guided through two off-axis parabolic mirrors to the quasi-static upper plate of the rheometer to gain maximum IR sensitivity. Thereby online and directly correlated real-time FTIR spectra can be acquired while simultaneously conducting rheological measurements. This allows for in situ correlation of macroscopic rheological properties with microscopic and molecular chemical changes. These experiments are conducted for a material under controlled conditions having exactly the same sample time evolution for both measurements. To demonstrate its potential, this newly developed method was applied to correlate the polymer network formation for a free-radical copolymerization of acrylic acid and methylenebis(acrylamide) as a crosslinking agent via IR spectroscopy and the respective mechanical time evolution, in a dilute water-based solution.

中文翻译：

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Rheo-IR：通过 FTIR 光谱和应变控制流变仪中的流变特性关联化学变化的组合装置

傅里叶变换红外 (FTIR) 光谱是一种常用的工具，可用于定性和定量地确定材料在固相、液相或气相中的化学成分。此外，它还可用作监测化学变化速率的技术。这些化学变化可能具有流变学相关性，例如聚合动力学、橡胶交联或环氧树脂固化，仅举几例。我们报告了用作衰减全反射 (ATR) 采样工具的 IR 透明上板流变几何学的设计。此外，我们描述了 ATR 晶体在 ARES G2 流变仪中的技术和方法适应，用于结合 FTIR 和流变测量。在这个新设置中，应变控制流变仪与 ATR 晶体相结合，红外光束通过两个离轴抛物面镜引导到流变仪的准静态上板，以获得最大的红外灵敏度。因此，在进行流变测量的同时，可以获得在线和直接相关的实时 FTIR 光谱。这允许宏观流变特性与微观和分子化学变化的原位相关性。这些实验是在受控条件下对两种测量具有完全相同采样时间演变的材料进行的。为了证明其潜力，这种新开发的方法被应用于通过红外光谱和各自的机械时间演变，在稀水中关联丙烯酸和亚甲基双（丙烯酰胺）作为交联剂的自由基共聚的聚合物网络形成 -基于的解决方案。