Precise structural analysis of multiphase polymeric nanocomposites remains a challenge even in the presence of high-quality X-ray diffraction data. This contribution thus addresses our attempt to formulate a combined analytical strategy for obtaining the atomic-resolution structure of multicomponent polymeric solids with complex nanodomain architecture. In this strategy, through the application of T₁-filtered solid-state NMR spectroscopy, the individual components are successively distinguished and selected, and the corresponding ¹H, ¹³C, and ¹⁵N isotropic chemical shifts are explicitly assigned. Thereafter, using an automated protocol allowing for processing and statistical analysis of large data sets, the experimentally determined NMR parameters are systematically compared with those DFT-calculated for the representative set of crystal structure predictions. Particular attention is devoted to the analysis of NMR parameters of hydrogen-bonded protons which are responsible for molecular packing. As a result of this search, the structures of micro- and nanosized crystallites dispersed in the polymeric matrix are determined and independently verified by the measurements of through-space dipolar couplings. The potential of this strategy is demonstrated on injectable polyanhydride microbeads consisting of a mixture of microcrystalline decitabine and nanocrystalline sebacic acid, both incorporated in the semicrystalline polymeric matrix of poly(sebacic acid). Through the synergistic interplay between the measurements, calculations, and the statistical analysis, we have developed an integrated approach providing structural information that is challenging to elucidate using conventional diffraction approaches. This combination of experimental and theoretical approaches enables one to determine the structural arrangements of molecules in situations which are not tractable by conventional spectroscopic techniques.

中文翻译：

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确定聚合物微珠内微和纳米晶体固体的原子分辨结构的有效策略：域编辑NMR晶体学

即使存在高质量的X射线衍射数据，多相聚合物纳米复合材料的精确结构分析仍然是一个挑战。因此，这一贡献解决了我们试图制定一种组合分析策略以获得具有复杂纳米域结构的多组分聚合物固体的原子分辨率结构的尝试。在此策略中，通过应用T ₁过滤的固态NMR光谱，可以连续区分和选择各个组分，并相应地选择¹ H，¹³ C和¹⁵明确指定了N个各向同性化学位移。此后，使用允许对大数据集进行处理和统计分析的自动化协议，将实验确定的NMR参数与DFT计算得出的代表晶体结构预测集的参数进行系统地比较。特别注意分析负责分子堆积的氢键质子的NMR参数。作为该搜索的结果，确定了分散在聚合物基质中的微米和纳米级微晶的结构，并通过对空间偶极耦合的测量来独立地对其进行验证。这种策略的潜力在可注射的聚酸酐微珠上得到了证明，该微珠由微晶地西他滨和纳米晶癸二酸的混合物组成，两者都掺入了聚癸二酸的半结晶聚合物基体中。通过测量，计算和统计分析之间的协同相互作用，我们开发了一种集成的方法，该方法可提供结构信息，而使用常规衍射方法难以阐明这些结构信息。实验方法和理论方法的这种结合使人们能够确定在常规光谱技术难以控制的情况下分子的结构排列。我们已经开发出一种集成的方法，该方法可提供结构信息，而使用传统的衍射方法难以阐明这些结构信息。实验方法和理论方法的这种结合使人们能够确定在常规光谱技术难以控制的情况下分子的结构排列。我们已经开发出一种集成的方法，该方法可提供结构信息，而使用传统的衍射方法难以阐明这些结构信息。实验方法和理论方法的这种结合使人们能够确定在常规光谱技术难以控制的情况下分子的结构排列。