弱电场驱动下高分子链在周期管道内输运的模拟研究

Simulation Study on the Migration of Polymer in Periodic Channels Under Weak Driving Force

采用Langevin动力学方法模拟研究了弱电场驱动下高分子链在无限长周期管道中的输运过程.管道由长度相等的α和β两部分周期排列而成,其中高分子链与α管道间存在相互吸引作用,而与β管道间存在纯排斥作用.模拟结果表明,高分子链在输运过程中存在明显的受限阶段,其逃离受限的方式与管道宽度有关且满足不同的规律.对于窄管道,高分子链在输运过程中呈直线伸展构型且运动具有"蛇爬行"特征.高分子链逃离受限过程伴随着整条链的运动,从而导致迁移率随高分子链长呈周期变化,而且在迁移率极值位置,高分子链投影长度与管道半周期之间存在简单的整数倍关系.对于宽管道,高分子链在输运过程中出现弯折构型且运动具有"蠕虫运动"特征.当链长比较长时,高分子链可通过链前端部分的伸长逃离受限,从而导致迁移率与高分子链长度无关.模拟结果可能有助于利用周期管道对不同长度的高分子链进行分离及可控输运.

The migration of polymer in periodical channels under weak electrical driving force was studied by Langevin dynamics simulation. The channel was patterned alternately by part α and part β with the same length. The interaction between polymer and channel α was attractive,while that between polymer and channelβ was purely repulsive. The results show that there are obvious trapped stages during the migration of polymer in periodical channels. The manner for polymer escaping from the trapped stage is dependent on the channel width. For narrow channel case,polymer keeps linear configuration and the movement seems like snake motion during the migration. The escape of polymer from the trapped stage needs the participation of the whole polymer,resulting that the mobility changes periodically with polymer length. At positions of the extreme point of the mobility,there are simple relations between the projected length of polymer and the period of the channel. For wide channel case,polymer keeps hair-pin or coil configuration and the movement seems like worm motion during the migration. Specially,when polymer is long,polymer can escape from the trapped stage by elongating the head part of the polymer,leading to the independent of the mobility on polymer length. The results may be helpful for polymer separation and controlled movement by using periodic channels.