Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China.
J Mol Model. 2010 Aug;16(8):1391-9. doi: 10.1007/s00894-010-0645-4. Epub 2010 Feb 16.
Hydrogen bonding among hard-hard segments and hard-soft segments in 4,4'-diphenylmethane diisocyanate (MDI)-based polyurethane was investigated theoretically by density functional theory (DFT). Both B3LYP/6-31G* and B3PW91/6-31G* methods gave good structures, reasonable Mulliken charges, binding energies, dipole moments, and good infrared (IR) spectra trends in predicting hydrogen bonding. Bond distances R(N-H...O), which were in the range of 3.005-3.028 A for the carbonyl bonded hydrogen-bond, and 3.074-3.075 A for the ester bonded hydrogen-bond, are in reasonable agreement with experimental values. Most of the carbonyl oxygen in polyurethane exists in a hydrogen-bonded form. Complex (c), with two carbonyl hydrogen bonds, features the largest dipole moment, while complex (d) with two ester hydrogen bonds, possesses the smallest dipole moment, i.e., lower than that of the isolated monomer, which may be due to the symmetry of the two monomers. These results confirm that the DFT method is a good tool with which to study weak interactions, and indicate that hydrogen bonds are indeed formed between carbonyl and N-H, or ester and N-H, with the former being stronger.
通过密度泛函理论（DFT）理论研究了 4,4'-二苯基甲烷二异氰酸酯（MDI）基聚氨酯中硬-硬段和硬-软段之间的氢键。B3LYP/6-31G和 B3PW91/6-31G方法都给出了良好的结构、合理的 Mulliken 电荷、结合能、偶极矩和良好的红外（IR）光谱趋势，可用于预测氢键。对于羰基键合的氢键，键距 R（N-H...O）在 3.005-3.028 A 范围内，对于酯键合的氢键，在 3.074-3.075 A 范围内，与实验值吻合较好。聚氨酯中大多数羰基氧都以氢键的形式存在。复合物（c）具有两个羰基氢键，具有最大的偶极矩，而具有两个酯氢键的复合物（d）具有最小的偶极矩，即低于单体的偶极矩，这可能是由于两个单体的对称性。这些结果证实了 DFT 方法是研究弱相互作用的有效工具，并表明羰基和 N-H 之间或酯基和 N-H 之间确实形成了氢键，前者更强。
