淀粉系高吸水性树脂反应中间体稳定性及反应活性的量子化学研究

运用abinitioUHF方法和DFTUB3LYP方法在6-31G基组水平下对淀粉系高吸水性树脂反应中间体的模型体系进行几何构型优化.针对每类自由基对应得到的两种典型的构象异构体(1_a,1_b和2_a,2_b),进行稳定性和反应活性分析.构型1_a和2_b的总能量相对较低.比较4个模型体系的前线分子轨道,构型1_a的能隙较小,同时HOMO能量较高,易给出电子,LUMO能量较低,易得电子,有利于电子转移,因而有较好的反应活性.自由基自旋密度主要集聚在C2或C3上,未有较大弥散,同时也是前线MO主要布居位置和重要的反应活性部位.对构型1_a与丙烯酸模型分子形成的复合物分析表明,两者的反应未经过过渡态,在瞬间即可完成.

Quantum Chemistry Study on Stability and Reactivity of Reactive Intermediate of Starch Super-water-absorbent Resin

The model geometries of reactive intermediates of the super-water-absorbent resin were determined by using ab inito UHF and density functional theory UB3LYP with 6-31G basis sets. The stability and reactivity of the two kinds of typical conformation isomers(1a, 1b and 2a, 2b) with their free radicals are obtained and analyzed. The calculation results show that the total energy of isomers 1a or 2b is lower. The energy gap of isomer 1a is smaller comparing with the frontier molecular orbitals of four model systems. HOMO energy of 1a is higher, so it is easy to lose electrons. LUMO energy is lower and it is easy to receive electrons, which benefits the charge transfer. The spin density of free radical mostly concentrates on C2 or C3 and has no large diffusion. They are the key part of reactivity. The analysis to the complex with isomer 1a and acrylic acid molecule indicate that the polymerization reaction is easy to finish because of giving out heat.