外力诱导吸附高分子单链的拉伸分子动力学研究

采用拉伸分子动力学方法研究聚乙烯单链在真空中从一个强吸附表面被拉伸的动力学过程. 当聚乙烯单链从中间1/3处被拉伸时，通过理想弹簧可测量其平均力〈f〉，发现在拉力与拉伸距离的曲线上出现了两个平台，这与实验结果非常一致，同时研究了在这个过程中链的形状变化情况，发现形状变化经历了四个阶段. 当聚乙烯单链的一端与吸附表面成一定倾斜角拉伸时，发现通过理想弹簧测量到的平均吸附力〈f〉与倾斜角θ在θ>20°的范围里总保持线性关系，并且其斜率随着拉伸速度的增加而增 关键词： 拉伸分子动力学 聚乙烯链 吸附现象

Steered molecular dynamics investigation of force-induced detachment of adsorbed single polymer chains

The dynamics of the detachment of single polyethylene (PE) chain from a strongly adsorbing surface in vacuum is investigated by steered molecular dynamics method. When the chain is pulled from the monomer of N/3 (here N is the chain length), there are two force plateaus for the curve of the average force 〈f〉 probed by the ideal spring as a function of pulling distance Z，which agrees well with the experimental results. There are four different stages during the detachment of single polyethylene (PE) chains. As the chains are pulled in an inclined direction from one end, there exist always a linear relationship for average force probed by the ideal spring vs inclination angle θ for θ>20 degrees Furthermore, the slope of the line increases with the pulling velocity. However, for θ<20 degrees, the average force probed by the ideal spring tends to a fixed value of 780pN.