Salamanca Fernando M, Zepeda-Rodríguez Zenen, Diñeiro Laura, Escrivá Marina M, Herrero Rebeca, Navarro Rodrigo, Valentín Juan L
Instituto de Ciencia y Tecnología de Polímeros (ICTP-CSIC), Juan de la Cierva 3, 28006 Madrid, Spain.
Polymers (Basel). 2023 Oct 11;15(20):4058. doi: 10.3390/polym15204058.
Low-field time-domain proton Nuclear Magnetic Resonance (NMR) spectroscopy is an attractive and powerful tool for studying the structure and dynamics of elastomers. The existence of crosslinks and other topological constraints in rubber matrices (entanglements and filler-rubber interactions, among others) renders the fast segmental fluctuations of the polymeric chains non-isotropic, obtaining nonzero residual dipolar couplings, which is the main observable of MQ-NMR experiments. A new software, Multiple quantum nuclear magnetic resonance analyzer for Elastomeric Networks v2 (MEW2), provides a new tool to facilitate the study of the molecular structure of elastomeric materials. This program quantitatively analyzes two different sets of experimental data obtained in the same experiment, which are dominated by multiple-quantum coherence and polymer dynamics. The proper quantification of non-coupled network defects (dangling chain ends, loops, etc.) allows the analyzer to normalize the multiple quantum intensity, obtaining a build-up curve that contains the structural information without any influence from the rubber dynamics. Finally, it provides the spatial distribution of crosslinks using a fast Tikhonov regularization process based on a statistical criterion. As a general trend, this study provides an automatic solution to a tedious procedure of analysis, demonstrating a new tool that accelerates the calculations of network structure using H MQ-NMR low-field time-domain experiments for elastomeric compounds.
低场时域质子核磁共振（NMR）光谱法是研究弹性体结构和动力学的一种有吸引力且强大的工具。橡胶基体中交联键和其他拓扑约束（如缠结和填料 - 橡胶相互作用等）的存在，使得聚合物链的快速链段波动呈现非各向同性，从而获得非零的残余偶极耦合，这是MQ - NMR实验的主要可观测值。一种新的软件，弹性体网络多量子核磁共振分析仪v2（MEW2），为促进弹性体材料分子结构的研究提供了一种新工具。该程序定量分析在同一实验中获得的两组不同的实验数据，这些数据主要由多量子相干和聚合物动力学主导。对未耦合的网络缺陷（悬垂链端、环等）进行适当的量化，使分析仪能够对多量子强度进行归一化，得到一条包含结构信息且不受橡胶动力学影响的累积曲线。最后，它基于统计标准，通过快速的蒂霍诺夫正则化过程提供交联键的空间分布。总的来说，这项研究为一个繁琐的分析过程提供了一种自动解决方案，展示了一种新工具，该工具利用低场时域H MQ - NMR实验加速了弹性体化合物网络结构的计算。
