Hoda Nazish, Kumar Satish
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Langmuir. 2007 Feb 13;23(4):1741-51. doi: 10.1021/la062088l.
The adsorption of single polyelectrolyte molecules onto surfaces decorated with periodic arrays of charged patches was studied using Brownian dynamics simulations. A free-draining, freely jointed bead-rod chain was used to model the polyelectrolyte, and electrostatic interactions were incorporated using a screened Coulombic potential with the excluded volume accounted for by a hard-sphere potential. The simulations predicted that the polyelectrolyte lies close to the adsorbing surface if the patch length, surface charge density, and screening length are sufficiently large. Chain conformations were found to be very sensitive to patch length, patch spacing, and the nature of the charge on adjacent patches. This is due both to the size of the polymer relative to patch length and spacing and to the structure of the electric field near the surface. In some cases, the component of the radius of gyration parallel to the surface can be made smaller than its free-solution value, which is contrary to what is observed for a uniformly charged surface. Isolated charged patches were also considered, and significant adsorption was observed above a critical surface charge density. The results demonstrate how polyelectrolyte conformations can be controlled by the design of the charged patches and may be useful for applications in which adsorbed polyelectrolyte films play a key role.
利用布朗动力学模拟研究了单链聚电解质分子在带有周期性排列带电斑块的表面上的吸附。使用自由排水、自由连接的珠-杆链来模拟聚电解质，并通过屏蔽库仑势纳入静电相互作用，同时通过硬球势考虑排除体积。模拟结果预测，如果斑块长度、表面电荷密度和屏蔽长度足够大，聚电解质会靠近吸附表面。发现链构象对斑块长度、斑块间距以及相邻斑块上电荷的性质非常敏感。这既归因于聚合物相对于斑块长度和间距的大小，也归因于表面附近电场的结构。在某些情况下，平行于表面的回转半径分量可以小于其在自由溶液中的值，这与在均匀带电表面上观察到的情况相反。还考虑了孤立的带电斑块，并且在临界表面电荷密度以上观察到显著的吸附。结果表明聚电解质构象如何通过带电斑块的设计来控制，并且可能对吸附聚电解质膜起关键作用的应用有用。
