Morávková Zuzana, Podešva Jiří, Shabikova Valeriia, Abbrent Sabina, Dušková-Smrčková Miroslava
Institute of Macromolecular Chemistry, Czech Academy of Sciences, 162 00 Prague, Czech Republic.
Molecules. 2025 Mar 21;30(7):1410. doi: 10.3390/molecules30071410.
Urea groups appear in many biomolecules and polymers. They have a significant impact on the properties of the materials because of their inherent strength and for their ability to participate in hydrogen bonds. Typically, in classical urea-based polymer materials, the urea groups occur in their ,'-disubstituted state. Recently, bis-aspartates have been introduced as a novel type of hindered amine resins providing, upon crosslinking with (poly)isocyanates, the polyurea-polyaspartate thermosets (PU-ASPE) for coatings, sealants, polyelectrolytes, and other applications. These materials contain ,''-trisubstituted urea linkages in their structures. However, the infrared (IR) characterization of trisubstituted urea groups has not been documented in sufficient detail. Consequently, studies on the structure of aspartate-based polyurea materials often rely on data from ,'-disubstituted ureas, which can lead to inaccurate conclusions. This study presents a detailed evaluation of the possible urea H-bonding states, focusing on the difference between the di- and trisubstituted species. Particularly, the attributions of the IR spectra to urea-based hydrogen bonding states are presented both in neat materials and their solutions. To systematize this study, we initially focus on a simple trisubstituted urea model system, tributyl urea (3BUA), and compare its spectral response with disubstituted -butyl-'-cyclohexyl urea (1B1CHUA) and trisubstituted -butyl-','-dicyclohexyl urea (1B2CHUA), to elucidate their hydrogen-bonding fingerprints. This research provides a thorough understanding of the IR response of the di- and trisubstituted urea species and their structural characteristics in urea-containing materials.
脲基存在于许多生物分子和聚合物中。由于其固有的强度以及参与氢键的能力，它们对材料的性能有重大影响。通常，在传统的基于尿素的聚合物材料中，脲基以其α,α'-二取代状态存在。最近，双天冬氨酸酯作为一种新型受阻胺树脂被引入，与（聚）异氰酸酯交联后可得到用于涂料、密封剂、聚电解质及其他应用的聚脲-聚天冬氨酸酯热固性材料（PU-ASPE）。这些材料的结构中含有α,α'',α''-三取代脲键。然而，关于三取代脲基的红外（IR）表征尚未有足够详细的记录。因此，对基于天冬氨酸的聚脲材料结构的研究往往依赖于α,α'-二取代脲的数据，这可能导致不准确的结论。本研究对可能的脲氢键状态进行了详细评估，重点关注二取代和三取代物种之间的差异。特别是，在纯材料及其溶液中都给出了红外光谱对基于尿素的氢键状态的归属。为了使这项研究系统化，我们首先关注一个简单的三取代脲模型体系，三丁基脲（3BUA），并将其光谱响应与二取代的α-丁基-α'-环己基脲（1B1CHUA）和三取代的α-丁基-α'',α''-二环己基脲（1B2CHUA）进行比较，以阐明它们的氢键指纹。这项研究全面了解了二取代和三取代脲物种在含脲材料中的红外响应及其结构特征。
