The influence of the counterion size on the conformational behavior of a single polyelectrolyte chain in a dilute solution in low-polar media has been studied by molecular dynamics. Modeling has been performed both for small counterions, which are smaller in size than the monomer unit, and for large counterions, which are several times larger in size than the monomer unit. It has been found that the chain gyration radius R_g depends nonmonotonically on the counterion size. The minimum value of R_g is observed when the size of counterions is comparable with the size of the monomer unit. The growth of R_g with increasing size of counterions results from the increasing contribution of excluded volume interactions, whereas its growth with decreasing size of counterions is due to the formation of elongated chains of dipoles. The dependence of the multiplet structure formed in media with strong electrostatic interactions on the fraction of charged chain units and the counterion size is analyzed.

通过分子动力学研究了抗衡离子大小对低极性介质稀溶液中单个聚电解质链构象行为的影响。既对尺寸小于单体单元的小抗衡离子，又对尺寸大于单体单元的数倍的大抗衡离子进行了建模。已经发现，链回转半径R _g非单调地取决于抗衡离子的大小。当抗衡离子的尺寸与单体单元的尺寸相当时，观察到R _g的最小值。R _g的增长抗衡离子尺寸增加的原因是排除体积相互作用的增加，而抗衡离子尺寸减小的原因是偶极子长链的形成。分析了在具有强静电相互作用的介质中形成的多重结构对带电链单元分数和抗衡离子尺寸的依赖性。