报告题目：charge partitioning in asymmetric diblock polyampholyte chains and polyelectrolyte complexes

报 告 人：Zuowei Wang (School of Mathematical and Physical Sciences)

报告时间：2015年5月21日(星期四)上午10：00-11:30

报告地点：嘉定园区学术活动中心302房间

报告摘要：

Complexation of oppositely charged macromolecules finds important applications in many scientific and engineering areas. Typical examples are the association of DNA with polycations used in gene therapy and the layer-by-layer assembly of oppositely charged polyelectrolytes (PE) for fabricating multilayer films.　In this work, we report computer simulation and scaling theory studies of the structural properties of single diblockpolyampholyte(PA) chains and complexes formed by a pair oppositely charged polyelectrolytes as a function of the electrostatic interaction strength and charge asymmetry.In the weak association cases where the electrostatic interaction energy between two nearest charges is no larger than kBT, three structural transition regimes are identified with the increase of the charge asymmetry. The diblock PA chains and the PE complexes are found to collapse into globular structures at low charge asymmetric cases, which can be described as the dense packing of oppositely charged electrostatic blobs, then transfer into tadpole-like structures each having an overcharged globular head and one- (PA chains) or two-(PE complexes) single-strand polyelectrolyte tails containing part of the extra charges in the intermediate asymmetric regime. In the high charge asymmetric regime, the globular head stretches into a double-strands structure due to the strong polarization effect.　The structural transitions in the strong association cases can also be divided into three regimes, but for the diblock PA chains the intermediate charge asymmetric regime is characterized by a tadpole structure with a globular head and a double-strand tail. Theoretical models based on the concept of electrostatic blobs and electrostatic energy of capacitors have been developed to describe these structural transitions. One essential result we revealed is that the overcharging in the globular or double-strands heads follows a universal behaviour, regardless of the electrostatic interaction strengths.