Yan Zhiwei, Zhang Rongchun
South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter (SESM), South China University of Technology, Guangzhou, 510640, PR China.
South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter (SESM), South China University of Technology, Guangzhou, 510640, PR China; Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology, Guangzhou, 510640, PR China.
J Magn Reson. 2023 Dec;357:107597. doi: 10.1016/j.jmr.2023.107597. Epub 2023 Nov 14.
Solid-state Nuclear Magnetic Resonance (NMR) has emerged as a pivotal technique for unraveling the microstructure and dynamics of intricate polymer and biological materials. Within this context, site-specific proton spin-lattice relaxation times in the laboratory frame (T) and rotating frame (T) have become indispensable tools for investigating phase separation structures and molecular dynamics in multiphase polymer systems. Notably, the site-specific measurement of proton T and T is usually achieved via C detection in polymers, where H polarization is typically transferred to C via cross polarization (CP). Nevertheless, CP relies on the H-C heteronuclear dipolar couplings, and thus it does not work well for the mobile components. In this study, via the integration of CP and RINEPT (refocused insensitive nuclei enhanced by polarization transfer), we propose a robust approach for the measurement of site-specific proton T and T in multiphase polymers. It overcomes the limitation of CP on transferring H polarization to C in mobile components, and thus enables simultaneous determination of site-specific proton T and T in rigid and mobile components in multiphase polymers in a single experiment. Such experiment can also be used for dynamics-based spectral editing due to the dynamic selectivity of CP- and RINEPT-based polarization transfer process. The proposed experiments are well demonstrated on three typical multiphase polymer systems, poly(methyl methacrylate)/polybutadiene (PMMA/PB) polymer blend, polyurethane (PU) and polystyrene-polybutadiene-polystyrene (SBS) elastomers. We envisage the proposed experiments can be a universal avenue for structural and dynamic elucidation of multiphase polymers containing both rigid and mobile components.
固态核磁共振（NMR）已成为解析复杂聚合物和生物材料微观结构与动力学的关键技术。在此背景下，实验室坐标系（T1）和旋转坐标系（T2）中特定位置的质子自旋 - 晶格弛豫时间已成为研究多相聚合物体系相分离结构和分子动力学不可或缺的工具。值得注意的是，质子T1和T2的特定位置测量通常通过聚合物中的碳检测来实现，其中氢极化通常通过交叉极化（CP）转移到碳上。然而，CP依赖于氢 - 碳异核偶极耦合，因此对于移动组分效果不佳。在本研究中，通过将CP和RINEPT（极化转移增强的重聚焦非灵敏核）相结合，我们提出了一种用于测量多相聚合物中特定位置质子T1和T2的稳健方法。它克服了CP在将氢极化转移到移动组分中的碳上的局限性，从而能够在单个实验中同时测定多相聚合物中刚性和移动组分的特定位置质子T1和T2。由于基于CP和RINEPT的极化转移过程的动态选择性，此类实验还可用于基于动力学的光谱编辑。所提出的实验在三种典型的多相聚合物体系，即聚（甲基丙烯酸甲酯）/聚丁二烯（PMMA/PB）聚合物共混物、聚氨酯（PU）和聚苯乙烯 - 聚丁二烯 - 聚苯乙烯（SBS）弹性体上得到了很好的验证。我们设想所提出的实验可以成为阐明同时包含刚性和移动组分的多相聚合物结构和动力学的通用途径。
