National Synchrotron Radiation Laboratory, Anhui Provincial Engineering Laboratory of Advanced Functional Polymer Film, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei 230026, China.
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.
Rev Sci Instrum. 2022 Mar 1;93(3):033905. doi: 10.1063/5.0080767.
An in situ stretching instrument combined with low field nuclear magnetic resonance (LF-NMR) was designed and developed, namely, Rheo-Spin NMR. The time resolved stress-strain curve together with the corresponding NMR signal can be simultaneously obtained. The Rheo-Spin NMR contains the functional modules, including (1) the in situ stretching module, (2) the NMR signal acquisition module, and (3) the cavity of the NMR positioning module. The unique ring-like shape of the sample is used to replace the traditional dumbbell sample due to limited space in the NMR probe, and the whole ring-like sample will be deformed during the uniaxial stretching process, which avoids the generation of interference signals from the undeformed sample. The designed stretching assembly made by zirconia ceramics is manufactured to match and stretch the ring-like samples. The strain rate can be tuned within the range of 10-10 s with the maximum stretching ratio λ of ∼3.8. The in situ stretching experiments combined with LF-NMR were carried out successfully with natural rubber of different fractions of carbon black. The time-resolved T relaxometry was adopted to evaluate segmental relaxation during uniaxial deformation which, for the first time, provides the direct and in situ molecular dynamics information. The Rheo-Spin NMR is promising to provide more in-depth insights into the structure and dynamics evolution of polymer products under real service conditions.
一种结合了低场核磁共振（LF-NMR）的原位拉伸仪器，即 Rheo-Spin NMR，被设计和开发出来。可以同时获得时分辨力的应力-应变曲线和相应的 NMR 信号。Rheo-Spin NMR 包含功能模块，包括（1）原位拉伸模块、（2）NMR 信号采集模块、（3）NMR 定位模块的腔室。由于 NMR 探头中的空间有限，采用独特的环形样品代替传统的哑铃形样品，整个环形样品在单轴拉伸过程中发生变形，从而避免了未变形样品产生干扰信号。设计的由氧化锆陶瓷制成的拉伸组件用于匹配和拉伸环形样品。应变率可以在 10-10 s 的范围内调节，最大拉伸比 λ约为 3.8。成功地对不同炭黑分数的天然橡胶进行了原位拉伸实验和 LF-NMR 实验。采用时分辨 T2 弛豫测量法来评估单轴变形过程中的分子段松弛，这首次提供了直接的原位分子动力学信息。Rheo-Spin NMR 有望为聚合物产品在实际使用条件下的结构和动力学演化提供更深入的见解。
