Study of the structure dependent behavior of polyelectrolyte in water

We examine the effect of pendant architecture on linear polyelectrolytes in solution using molecular dynamics simulations. A comparison is done between the standard bead-spring polyelectrolyte system and a system which has the charged beads pendant to neutral backbone beads. Recent simulations of ionomer melts have found significant differences in the structure between the two architectures, but we find the structure is not dramatically affected by the different geometry. In general, the backbone architecture is slightly more compact than the pendant architecture. The counterion condensation is typically larger for the backbone systems, which yields the more compact structures. Only when both the Bjerrum length is much larger than the spacing between charges and the spacing between pendants is twice the backbone bead spacing, is the peak in the monomer-counterion radial distribution function larger for the pendant architecture. The radius of gyration for the pendant remains larger than backbone architecture because of the extra excluded volume of the pendant.