Collapse of Linear Polyelectrolyte Chains in a Poor Solvent: When Does a Collapsing Polyelectrolyte Collect its Counterions?

Abstract

In order to better understand the collapse of polyions in poor solvent conditions the effective charge and the solvent quality of the hypothetically uncharged polymer backbone need to be known. In the present work this is achieved by utilizing poly-2-vinylpyridine quaternized to 4.3% with ethylbromide. Conductivity and light scattering measurements were utilized to study the polyion collapse in isorefractive solvent/non-solvent mixtures consisting of 1-propanol and 2-pentanone, respectively, at nearly constant dielectric constant. The solvent quality of the uncharged polyion could be quantified which, for the first time, allowed the experimental investigation of the effect of the electrostatic interaction prior and during polyion collapse, by comparing to a newly developed theory.Although the Manning parameter for the investigated system is as low as l B /l = 0.6 (l B the Bjerrum length and l the mean contour distance between two charges), i.e. no counterion binding should occur, a qualitative interpretation of the conductivity data revealed that the polyion chain already collects its counter ions when the dimensions start to shrink below the good solvent limit but are still well above the θ-dimension.

Charge regularization in phase separating polyelectrolyte solutions

“…[39][40][41][42][44][45][46][47][49][50][51][53][54][55][56] A particular example is the case of aqueous solutions of sodium polystyrene sulfonate containing some divalent salts such as barium chloride. 39,40,47,51,55 The system now becomes more complex with many components: polymer, counterion, cation, and anion of the added salt and solvent.…”

“…There have also been manifestations of the same effect in several other situations involving brushes 24,25 and single chains. 23,[26][27][28][29][30] In addition to these theoretical arguments, computer simulations [31][32][33][34][35][36][37][38] and experiments [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] have shown clearly that the effective charge of the polymer varies as the experimental variables change.…”

50th Anniversary Perspective: A Perspective on Polyelectrolyte Solutions

“…As a straightforward example, consider the coil-to-globule transition of a flexible polyelectrolyte chain as the temperature is lowered or the dielectric constant is lowered or salt concentration is increased. 44 The coil-to-globule transition of an uncharged polymer is addressed in terms of attractive two-body interaction (with the Flory–Huggins χ parameter being larger than 0.5) and a stabilizing (repulsive) three-body interaction parameter w 3 . When w 3 is higher, lower temperature is required to induce the coil-to-globule transition.…”

Regimes of electrostatic collapse of a highly charged polyelectrolyte in a poor solvent

“…It is more challenging, however, to study a collapsed state of a flexible PE in a poor solvent [35][36][37][38][39][40][41] since, unlike in a good solvent, there exist additional attractive interactions between monomers which compete with the repulsive part of electrostatic interactions. The valency of counterions determines the number of counterions condensed inside the collapsed globule and hence affects the monomer-monomer distance and thereby modifies the attractive volume interactions.…”