Pearl-Necklace-Like Chain Conformation of Hydrophobic Polyelectrolyte:  a SANS Study of Partially Sulfonated Polystyrene in Water

Abstract

The form factor of partially sulfonated polystyrene PSSNa (degree of sulfonation f =1, 0.72, 0.64 and 0.36), at polymer concentration 0.17M and 0.34M, without or with added salt (0 M, 0.34M, & 0.68M), is measured by Small Angle Neutron Scattering using the Zero Average Contrast method. The total scattering function is also measured, allowing us to extract the distinct interchain function and an apparent structure factor. The main result is the behavior of the form factor which shows contributions of spherical entities as well as extended chain parts. This is striking for 0.64, while for f = 0.36 the sphere contribution is more dominant. The conformation does not depend on polymer concentration. When salt is added, the sphere sizes do not vary, but the contribution Spiteri et al. Form factor of partially sulfonated polystyrene 2 attributed to the stretched parts does vary very much like for fully sulfonated PSSNa. Discussion of the interchain contribution permits to establish the level of interpenetration: solutions are interpenetrated for f= 0.64, and at the limit for f=0.36. The theoretical pearl necklace model appears very suitable to modeling the results. Comparisons are made with analytical calculation and simulation data of pearl necklace. While the respective roles of Rayleigh transition, heterogeneous architecture, and strong hydrophobicity of non sulfonated PS monomers remain under discussion, the data give an accurate three dimensional image of the pearl necklace in solution.

From a melt of rings to chromosome territories: the role of topological constraints in genome folding

“…The initial formation of territory-like regions is also observed in computer simulations and to a certain extent by scattering experiments of polyelectrolyte gels and solutions [153][154][155][156]. Upon change in solvent quality or counterion valency the systems start to shrink by chain contraction.…”

Arrangements of cationic starch of varying hydrophobicity on hydrophilic and hydrophobic surfaces

“…This is probably caused by the fact that, in low electrolyte concentration, the conformation of polymer in solution is rather extended because of the strong repulsive electrostatic interactions between the charged segments. Generally, necklace-like structures are expected to consist of highly collapsed globules separated by stretched segments or strings and the formation of these structures has been speculated to take place in systems where the compatibility between the polyelectrolyte and the solvent is poor [36,37]. Aqueous electrolyte solutions are, however, good solvents for cationic starch.…”

Kinetics of charged polymer collapse: effects of additional salt

“…In Figure 2 we present the time evolution of the conformational landscape of the PE chain of length N = 400 for three different valencies of counterions along the collapse trajectory. The collapsing of PE initiates with the formation of many small clusters connected by linear segments monomers analogous to the pearl-necklace phase described in the literature 43,48,[62][63][64][65][66][67] . The clusters then absorb the remaining monomers, resulting in the compaction of the polymer to form very few large clusters along the PE chain, typically at the two ends of the PE chain connected by bridge of monomers, reminiscent of the dumbbell-like configuration 68,69 .…”