0000000000113637
AUTHOR
Murugappan Muthukumar
Apparent Molar Mass of a Polyelectrolyte in an Organic Solvent in the Low Ionic Strength Limit As Revealed by Light Scattering
The apparent molar mass of a partially quaternized poly-2-vinylpyridines (degree of quaternization 4.3% < Q < 35%) in 1-propanol is measured by light scattering at low ionic strength (10–6 M < cs < 10–3 M) as a function of polyion repeat unit concentration (7 × 10–5 monomol/L < cm,p < 4 × 10–2 monomol/L). No dialysis was applied prior to measurements. The apparent molar mass under “salt-free” conditions is smaller than the true molar mass by an order of magnitude, while approaching the true value at higher ionic strength. Concomitant data on the dependence of scattering intensity on scattering wave vector show that the dilute polyelectrolyte solutions are strongly correlated. A recent theor…
The Electrostatic Expansion of Linear Polyelectrolytes: Effects of Gegenions, Co-ions, and Hydrophobicity
The molar mass and ionic strength dependence of the dimensions of hydrophobically modified poly(vinylpyridinium) cations are demonstrated to be almost perfectly described by a theoretical expression derived on the basis of only excluded volume considerations. Generally, the effective charge density of the polyions decreases significantly with increasing hydrophobicity and with increasing polarizability of the gegenions. Unexpectedly, the intrinsic excluded volume effect which becomes dominating at high ionic strength not only depends on the hydrophobicity of the polyion but also significantly increases with decreasing polarizability of the gegenions (i.e., if the iodide gegenions are replac…
Collapse of Linear Polyelectrolyte Chains in a Poor Solvent: When Does a Collapsing Polyelectrolyte Collect its Counterions?
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/nonsolvent 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 intera…