Conductometric properties of linear polyelectrolytes in poor-solvent condition: The necklace model

Abstract

We present a set of low-frequency electrical conductivity measurements of solutions of differently charged, salt-free polyelectrolytes in poor- and in good-solvent conditions, in the semidilute concentration regime. The data have been analyzed and discussed in light of the necklace model for hydrophobic polyelectrolytes recently proposed by Dobrynin et al. [Macromolecules 29, 2974 (1996)] that predicts the chains to collapse into spheroidal cores connected by narrow strings. By varying the quality of the solvent, we have measured the polyion equivalent conductance lambda(p) in an extended concentration range in the semidilute regime and have demonstrated that this parameter is influenced by the polyion chain conformation, giving further support, when the poor-solvent condition prevails, to the picture of a string of electrostatic blobs. On the contrary, in good-solvent condition, the electrical conductivity data are in reasonable good agreement with the picture of an extended chain consisting of a collection of electrostatic blobs. These electrical conductivity measurements, in light of scaling theory, furnish new experimental support for the necklace model for hydrophobic polyions in poor solvents.

Transport properties of some cationic polysaccharides

“…For example, the question whether counterion condensation is a threshold phenomenon is still a matter of debate. According to some authors there is a critical value for ξ [26][27][28][29], but according to the others the counterion condensation can also occur below ξ c [21,30,31]. The investigation of transport properties, such as viscosity and conductivity, is very useful in the study of polyion-counterion interactions in dependence on some experimental variables affecting the polyion charge density.…”

“…These interactions are strongly sensitive to some parameters such as the chain length, the charge density, the polyelectrolyte concentration, the counterion type, the ionic strength, the solvent polarity, etc. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Perhaps the most significant parameter affecting the solution properties of a polyelectrolyte is the linear charge density whose importance has been promoted by Manning in his counterion condensation theory [24,25].…”

Does Electrical Conductivity of Linear Polyelectrolytes in Aqueous Solutions Follow the Dynamic Scaling Laws? A Critical Review and a Summary of the Key Relations

“…We confine ourselves to one's own measurements [4,5,8,12], but in the recent literature many other appropriate examples can be easily found.…”

“…The second example is taken from reference [12]. We have investigated the electrical behavior of poly(N-methyl-2-vinyl pyridinium chloride) [PMVP-Cl] at two different charge densities in two different solvents, i.e., pure water (poor-solvent condition) and ethylene glycol (good-solvent condition).…”

“…In this review, we summarize the main results and collect the relevant expressions governing the electrical conductivity of a polyelectrolyte solution in different experimental conditions, on the basis of a series of our own papers, appeared in the last few years [4][5][6][7][8][9][10][11][12][13][14][15][16].…”