Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany.
J Chem Phys. 2021 Oct 7;155(13):134901. doi: 10.1063/5.0065572.
Nonlinear rheological properties of viscous indomethacin are studied in the frequency range of its structural relaxation, that is, in a range so far inaccessible to standard techniques involving medium-amplitude oscillatory shear amplitudes. The first- and third-order nonlinearity parameters thus recorded using a sequence of small and large shear excitations in a time efficient manner are compared with predictions from rheological models. By properly phase cycling the shear amplitudes, build-up and decay transients are recorded. Analogous to electrical-field experiments, these transients yield direct access to the structural relaxation times under linear and nonlinear shearing conditions. To demonstrate the broader applicability of the present approach, transient analyses are also carried out for the glass formers glycerol, ortho-terphenyl, and acetaminophen.
粘性吲哚美辛的非线性流变性质在其结构弛豫的频率范围内进行研究，即在一个到目前为止无法通过涉及中振幅振荡剪切幅度的标准技术来访问的范围内。使用小和大剪切激励的序列以有效的方式记录的一阶和三阶非线性参数与流变学模型的预测进行了比较。通过适当的相循环剪切幅度，记录了建立和衰减瞬变。类似于电场实验，这些瞬变为线性和非线性剪切条件下的结构弛豫时间提供了直接的访问。为了证明本方法的更广泛适用性，还对玻璃形成剂甘油、邻三联苯和醋氨酚进行了瞬变分析。
