Polyelectrolyte complexes, 1. The effect of pH and ionic strength on the stoichiometry of model polycation—polyanion complexes

Abstract

The interactions between model polycations and polyanions have been studied using the fluorescent dye acridine orange as a probe. The dye emission at 540 nm is quenched by the addition of polyanions, a process which is reversed by the addition of certain polycations. Techniques have been developed which enable a determination of the stoichiometry of polyelectrolyte complexes so formed between three polyanions (carboxymethylcellulose, K-carrageenan and poly(styrenesu1fonate)) and two polycations [poly(L-lysine hydrobromide) and poly(p-xylylviologen dibromide)) . A one to one pairing of acidic sites with basic groups was observed over a wide range of temperature, pH and ionic strength. Deviations from unit stoichiometry in the presence of multi-charged metal ions have been interpreted as due to conformational changes in the polyanion. Results from viscosity measurements are included which suggest the neutralisation of charged groups in the polyelectrolyte complex.

Polyelectrolyte complexes. II. Specific aspects of the formation of polycation/dye/polyanion complexes

“…The release of the dye from a polyanion/ cationic dye complex by the addition of a polycation has already been reported. 15 The increasing of the free dye concentration in aqueous solution, after the addition of polycation, was in conjunction with polycation binding into the polyanion/ dye complex, in that case. The ability of the interpolyelectrolyte complexes to bind dyes was also mentioned.…”

“…It has been reported that the dye is displaced by the addition of a polycation to stoichiometric polyanion/dye complexes. 15,16 Formation of interpolyelectrolyte complexes (PECs) was extensively studied, 16 -18 but parameters that cause the formation of poly-mer/small organic compound/polymer complexes have not been as well explored. In previous articles, we reported on water-insoluble PECs containing poly(N,N-dimethyl-2-hydroxypropylene ammonium chloride), with different degrees of branching, as the cationic component and poly(sodium acrylate) (NaPA), 19 or poly(sodium 2-acrylamido-2-methylpropane sulfonate) (NaPAMPS) 20 as the anionic component.…”

Influence of Nonstoichiometry on the Viscoelastic Properties of a Polyelectrolyte Complex

“…In contrast, Michaels and co-workers found no counterions within PECs, indicating both 1:1 stoichiometry and efficient pairing . Cundall et al came to the same conclusion using fluorescent counterions for Pol – . Unfortunately, the displacement of fluorescent counterions from Pol – does not reveal excess or overcompensation by Pol + .…”

“…While preparing PECs simply by mixing polyelectrolyte, usually in aqueous solutions, is straightforward, the resulting material may not be a stoichiometric mixture with equal numbers of Pol + and Pol – . − If the PEC composition is nonstoichiometric, additional counterions are required to balance the leftover polymer charge, as shown in Scheme .…”

Nematocysts (stinging capsules of Cnidaria) as Donnan‐potential‐dominated osmotic systems

“…This procedure was repeated twice to guarantee equilibrium conditions. Immediately afterwards nematocysts were checked for red (cooperative binding of acridine orange) or green fluorescence (normal binding) [24] in a Zeiss photomicroscope I11 equipped with a 111 RS condenser, a BP 405/FT 425 filter set and a mercury HBO 50-W lamp. By this method limiting salt concentrations (concentrations which just inhibit a red fluorescence of the nematocyst interior) could be determined within a range of at least 0.1 in the log/log plot of Fig.…”