低聚壳聚糖几何结构和物理化学属性的理论研究  

Theoretical study on geometry and physical and chemical properties of oligochitosan

作　　者：李鑫[1] 张梁[1] 羊梦诗[1] 储修祥[2] 徐灿[3] 陈亮[2] 王悦悦[2] 

机构地区：[1]浙江农林大学工程学院,临安311300 [2]浙江农林大学理学院,临安311300 [3]兰州大学磁学与磁性材料教育部重点实验室,兰州730000

出　　处：《物理学报》2014年第7期255-261,共7页Acta Physica Sinica

基　　金：国家杰出青年科学基金(批准号:50925103);浙江省教育厅科研基金(批准号:Y201225803);2014年浙江省新苗人才计划项目资助的课题~~

摘　　要：运用密度泛函B3LYP/6-31G+(d)方法对gg构象的低聚壳聚糖进行了结构优化、频率计算和电子结构,并用更高精度的WB97XD/6-311+G(d,p)方法计算了平均结合能及零点能校正,分析了热力学性质.结果表明,由于低聚壳聚糖中的氢键作用,使其形成螺旋结构;聚合度的增加,使平均结合能随之下降,结构的稳定性增强;在降解过程中,均为放热反应,验证了利用降温来提高降解产率的实验的可行性;此外,聚合度的增加,使能隙减小且快速收敛于聚合度为7的6.99 eV,稳定的反应活性与实验相符;HOMO、LUMO的电子密度分布表明,化学活性集中在C2位的氨基、C6位的羟基以及链的两端位置.该结果对低聚壳聚糖模型的建立和低聚壳聚糖降解过程、活性位置以及物理化学属性的尺寸依赖等现象的研究有着指导意义.By using the density functional theory with B3LYP/6-31G＋（d） we compute the optimization, vibration frequencies, electron structures of gg conformation of oligochitosans, and study the average binding energies and the zero-point energy corrections using WB97XD method. We also analyze the thermodynamic properties of oligoehitosans. Results show that the hydrogen-bond makes the oligochitosan become spiral; average binding energies tend to decrease and stability tends to improve with the increasing degree of polymerization （DP）; the water degradation of oligochitosan is an exothermic reaction, so it is feasible to reduce the temperature to improve the degradation yield in experiment; in addition, the energy Eap of oligochitosan quickly converges to 6.99 eV with the increase of DP; furthermore, the value of DP7 oligochitosan is in accordance with the convergence value. The HOMO and LUMO of oligochitosan show that chemical activity is mainly distributed in C2 amino, C6 hydroxyl groups, and both ends of oligochitosan chain. These results have instructive significance on the modeling, and can provide a theoritical basis for degradation process, chemical activity position, and size-dependence in physical chemical properties of oligochitosan.

关 键 词：低聚壳聚糖 几何结构 尺寸效应 电子性质 

分 类 号：O469[理学—凝聚态物理]