Conformational Study of Polyelectrolytes under solvophilic and solvophobic conditions

The scaling theory for polyelectrolyte solutions¹ predicts the conformation of polyelectrolytes under different conditions. A partially collapsed necklace conformation of polyelectrolytes under solvophobic conditions has been experimentally reported², in agreement with earlier theoretical and simulation work. Though similar conformations have been predicted under some solvophilic environments at low dielectric constants (ε), experimental studies on the influence of solvent permittivity on polyelectrolyte conformation have not been performed.



Here, we use small-angle scattering behaviour to study the structure of polystyrene sulfonate in solution under solvophobic and solvophilic conditions. We show that a transition from a scaling of the correlation length (ξ) with concentration from ξ ≈ c^-1/2 to ξ ≈ c^-1/3 occurs as the dielectric constant of the solvent is lowered beyond ε ≈ 25, indicating the partial collapse of PSS chains. This transition is observed under solvophobic and solvophilic conditions. In the latter case, where monomer-monomer interactions are repulsive, chain collapse is thought to arise from attractive forces originating between condensed counterions³.

References:

1. Dobrynin, A., Colby, R. and Rubinstein, M., 1995. Macromolecules, 28(6), pp.1859-1871.

2. Spiteri, M.N., Williams, C.E. and Boué, F., 2007. Macromolecules, 40(18), pp.6679-6691.

3. Jeon, J. and Dobrynin, A.V., 2007. Macromolecules, 40(21), pp.7695-7706.