The molecular structure of a crosslinked nitrogen-rich resin made from melamine, urea, and aldehydes, and of microcapsules made from the reactive resin with multiple polymeric components in aqueous dispersion, has been analyzed by ¹³C, ¹³C{¹H}, ¹H–¹³C, ¹H, ¹³C{¹⁴N}, and ¹⁵N solid-state NMR without isotopic enrichment. Quantitative ¹³C NMR spectra of the microcapsules and three precursor materials enable determination of the fractions of different components. Spectral editing of non-protonated carbons by recoupled dipolar dephasing, of CH by dipolar DEPT, and of C–N by ¹³C{¹⁴N} SPIDER resolves peak overlap and helps with peak assignment. It reveals that the N- and O-rich resin “imitates” the spectrum of polysaccharides such as chitin, cellulose, or Ambergum to an astonishing degree. ¹⁵N NMR can distinguish melamine from urea and guanazole, NC=O from COO, and primary from secondary amines. Such a comprehensive and quantitative analysis enables prediction of the elemental composition of the resin, to be compared with combustion analysis for validation. It also provides a reliable reference for iterative simulations of ¹³C NMR spectra from structural models. The conversion from quantitative NMR peak areas of structural components to the weight fractions of interest in industrial practice is derived and demonstrated. Upon microcapsule formation, ¹⁵N and ¹³C NMR consistently show loss of urea and aldehyde and an increase in primary amines while melamine is retained. NMR also made unexpected findings, such as imbedded crystallites in one of the resins, as well as persistent radicals in the microcapsules. The crystallites produce distinct sharp lines and are distinguished from liquid-like components by their strong dipolar couplings, resulting in fast dipolar dephasing. Fast ¹H spin–lattice relaxation on the 35-ms time scale and characteristically non-exponential ¹³C spin–lattice relaxation indicate persistent radicals, confirmed by EPR. Through ¹H spin diffusion, the mixing of components on the 5-nm scale was documented.

由三聚氰胺，尿素和醛制成的交联富氮树脂的分子结构，以及由具有多种聚合物组分的反应性树脂制成的微胶囊在水分散液中的分子结构已通过¹³ C，¹³ C { ¹ H}，^{1进行了分析。} H- ¹³ C，¹ H，¹³ C { ¹⁴ N}和¹⁵ N固态NMR，无同位素富集。微胶囊和三种前体材料的定量¹³ C NMR光谱能够确定不同组分的分数。通过重耦合偶极相移来对非质子化碳进行光谱编辑，通过偶极DEPT对CH进行光谱编辑，以及通过重耦合DE对C–N进行光谱编辑¹³ C { ¹⁴ N}蜘蛛可以解决峰重叠问题，并有助于峰分配。它表明，富含N和O的树脂以惊人的程度“模仿”了诸如几丁质，纤维素或龙涎香等多糖的光谱。¹⁵ N NMR可以区分三聚氰胺与尿素和胍基，NC = O与COO，伯与仲胺。这种全面而定量的分析可以预测树脂的元素组成，并将其与燃烧分析进行比较以进行验证。它还为^13的迭代仿真提供了可靠的参考结构模型的13 C NMR光谱。得出并证明了在工业实践中从结构组分的定量NMR峰面积到感兴趣的重量分数的转换。在形成微胶囊后，¹⁵ N和¹³ C NMR始终显示出尿素和醛的损失以及伯胺的增加，同时保留了三聚氰胺。NMR还提供了出乎意料的发现，例如其中一种树脂中嵌入了微晶，以及微胶囊中的持久性自由基。微晶产生明显的清晰线条，并通过其强的偶极耦合与液体状成分区分开，从而导致快速的偶极移相。35毫秒时间尺度上快速的¹ H自旋-晶格弛豫和典型的非指数¹³C自旋-晶格弛豫表明持久的自由基，由EPR证实。通过¹ H自旋扩散，记录了5 nm规模的组分混合。