The use of an automatic, continuous mixing (ACM) technique, coupled with multiangle static light scattering, refractometric, and viscometric detectors allowed detailed measurements of electrostatic effects in polyelectrolyte solutions to be made while varying ionic strength [I], and polyelectrolyte concentration. A linear polyelectrolyte, sodium hyaluronate (HA) was used. The behavior of second and third virial coefficients, A 2 and A3, the angular scattering envelope, and the reduced viscosity were determined simultaneously. The crossover regime from where interparticle effects dominate the scattering to where single particle form factors dominate is clearly seen and is rationalized by a simple pair correlation function. Good agreement is found for polymer dimensions and A2 using a combination of electrostatic persistence length and electrostatic excluded volume theories, with no adjustable parameters. The contribution to [I] from the HA counterions is observed via the electroviscous effect, a reduced viscosity crossover phenomenon, and an unusual scattering minimum vs polyelectolyte concentration at low [I].

An automatic, continuous-mixing technique is introduced to measure light scattering and viscosity simultaneously over a wide range of solute concentrations in multicomponent systems. Behavior along arbitrary curves in component coordinates can be monitored. This technique is used to investigate the association and electrostatically based excluded-volume interactions that arise in solutions of interacting neutral polymers and charged micelles. In this study, the ionic surfactant sodium dodecyl sulfate (SDS) and a neutral polymer poly(vinylpyrrolidone) (PVP) were chosen. The SDS confers pseudopolyelectrolyte properties on the polymer/micelle aggregates (PSA), such as electrostatically enhanced second and third virial coefficients A2 and A3, respectively. The presence of a large A3 is directly observed as a well-defined maximum in scattering intensity versus [PVP] under saturating SDS conditions. The electrostatically enhanced three-body effects represented by A3 in light scattering are nearly 3 orders of magnitude greater than the corresponding three-body terms in viscosity. A viscosity effect reminiscent of the electroviscous effect seen for linear polyelectrolytes is observed, but it occurs under very different PSA concentration and solution ionic strength conditions.

The effect of added electrolyte (AE) valence and species on polyelectrolytes was studied using automatic, continuous mixing (ACM), allowing measurements over composition gradients. The second virial coefficient A 2 was decomposed into contributions from an electrostatically sensitive meansquare gyration radius 〈S 2 〉 and an external electrostatic field. 〈S 2 〉 matched predictions of combined electrostatic persistence length and excluded-volume theories, without adjustable parameters. A2 was modeled via an equivalent, soft-core, expansible, charged sphere. Whereas the scaling behavior of 〈S 2 〉, intrinsic viscosity [η], and A2 was the same for all AE, the prefactors strongly depended on AE symmetry and valence. At given ionic strength 〈S 2 〉, [η], A2, effective linear charge density, and expansible sphere surface potential are less for divalent than monovalent AE. Different ion species for a given valence class showed second-order effects following a Hoffmeister series. ACM should also prove valuable for investigating AE-induced phase transitions in polyelectrolytes like DNA and proteins.

A phenomenon was observed near the critical micelle concentration (cmc) of surfactants using static light scattering. This consists of an unexpected peak in light scattering as the concentration varies between zero and above the cmc. This work studied three different surfactants: the two ionic surfactants hexadecyltrimethylammonium bromide (CTABr) and sodium dodecyl sulfate (SDS) and the nonionic surfactant Triton X-100. Peaks were observed for all three under different conditions such as varying ionic strengths and different concentration paths. These peaks are real, are reproducible, and appear to have static properties.

Using automatic, continuous online monitoring of polymerization reactions (ACOMP) the final, divergent growth phase (FDGP) of the condensation polymerization of dimethylamine, epichlorohydrin, and ethylenediamine was monitored, which produced a highly ramified, polyelectrolytic polyamine. The weight average mass, M w, increased exponentially during the FDGP, whereas weight averaged intrinsic viscosity [η]w increased slowly, reaching a plateau. Multi-detector gel permeation chromatography (GPC) revealed that polymers of mass 20 000 to 106 are branched and self-similar, but above this mass, [η] increases less strongly with M. This appears to be due to higher order ramification, a precursor to gelation. The ACOMP trends in M w and [η]w provide direct online evidence of this process. It is shown computationally that a mere increase in polydispersity cannot explain this behavior. GPC showed the mass distribution becomes highly asymmetric as conversion increases. A plausible kinetic model for the distribution asymmetry is introduced, and a complementary model for the effects of higher order ramification on [η]w.