有机分子超薄膜的结构对摩擦的影响

摘要

Molecular dynamics simulation is used to study the friction of mixed Langmuir-Blodgett film composed of hydrocarboxylic acid（C_nH_（2n＋1）COOH,n = 12,13,14,15,16,17） and the C_（17）H_（31）COOH,in order to investigate the influence of the structure on friction.The results show that the restiction of long chain molecules by the neighbor molecules increases and the monolayers become more steady as n increases,while the shear pressure between the monolayers decreases and reaches a minimum when n = 17.The hydrogen-bond formed in the mixed monolayers is the main reason why the monolayers become more steady,espatially,the hydrogenbonds are most steady when n = 16,but the monolayer composed that just of C_（17）H_（31）COOH molecules has the best sliding effect; there is no hydrogen-bond between the two monolayers.The shear pressure is hardly affected by the molecular deformation.%采用分子动力学方法,模拟了由脂肪酸C_nH_（2n＋1）COOH和C_（17）H_（31）COOH（n=12,13,14,15,16,17）组成的混合单层Langmuir-Blodgett（LB）膜间的摩擦特性,探究了膜结构的变化对超薄膜的摩擦的影响.结果显示.在滑动过程中,随着n的增加,膜内分子的运动受到邻近分子的约束逐渐增加,膜结构的稳定性也逐渐增加,其剪切压逐渐减小,n=17时的剪切压最小.在两单层膜之间无氢键形成;而混合膜内的分子之间形成的氢键是单层膜结构稳定的主要因素,其中n=16时形成的氢键最稳定,但全部由相同C_（17）H_（31）COOH分子组成的单层膜的滑动效果最好.分子的弯曲形变能对剪切压影响非常小.