Automatic Continuous Mixing

Automatic Continuous Mixing was developed by us as a useful technique in studying equilibrium and quasi-equilibrium processes. The motivation is to be able to analyze complex, multi-component systems, increase the resolution of experiments, and allow for higher sample throughput.

It basically includes a programmable mixing pump, operating in step gradient mode or continuous gradient mode, connected to a flexible detector train, with a multi-angle light scattering detector, viscometer, RI and UV detectors.

Many types of characterizations are possible:

• two-component polymer solutions; Mw, A2 , A3 , [h]w are simultaneously obtained by automatic dilution of a polymer solution into the solvent . Compared to the traditional Zimm plot method, ACM has more accuracy (provides continuum of points), reduces sample preparation time, offers complete information on the polymer sample analyzed.
• polyelectrolyte effects;
• polymer - polymer interactions
• polymer - surfactant interactions;
• surfactants-aromatics;

Typical Results

• Polyelectrolyte effects: the increase in scattering as electrostatic shielding leads to the decrease in A2 and A3, and the contraction of the polyelectrolyte coil, leading to decreased viscosity.

Raw voltages during CaCl2 ramp at fixed polyelectrolyte concentration (sodium hyaluronate, 0.1mg/ml)

• Association of charged micelles with neutral polymers - due to the association with SDS micelles, the polymer becomes charged, a 'pseudopolyelectrolyte'.

[SDS] ramp into PVP salt free solution (c= 0.002 g/cm3 , Mw =2x106 g/M)

• ACM as a complementary technique for ACOMP: the bimodality in the copolyelectrolyte/neutral polymer blend (VB/Aam) affects the interparicle interactions, seen in the A2 and A3 behavior.

Kcp/I(q=0) vs. cp for a copolyelectrolyte/neutral polymer blend (VB/Aam) produced at 0.100M NaCl, at [NaCl] =0.010M. The inset shows A2 and A3 vs. ionic strength.

• ACM for interaction of aromatics and surfactants: The striking effect that the aromatic has on intermicellar interactions (left); The abrupt change in A2 as the non-ionic surfactant fills with aromatic molecules and its volume becomes saturated with them (right).

Raw light scattering voltages vs. total (aromatic+surfactant) concentration. A2 for (aromatic+surfactant) solutions vs. Caromatic.

ACM Publications appeared or in press

1. E. Bayly, J. L. Brousseau and W. F. Reed, "Continuous Monitoring of the Effect of Changing Solvent Conditions on Polyelectrolyte Conformations and Interactions", Int. J. of Pol. Charact. and Analysis 2002, 7, 1-19.

2. G. A. Sorci; W. F. Reed, "Electrostatic and Association Phenomena in Aggregates of Polymers and Micelles", Langmuir 2002, 18(2), 353-364.

3. G. A. Sorci; W. F. Reed, "Electrostatically enhanced second and third virial coefficients, viscosity and interparticle correlations for linear polyelectrolytes", Macromolecules 2002, 35(13), 5218-5227.

4. W. F. Reed, "Automatic, Continuous Mixing Techniques for Online Monitoring of Polymer Reactions and for the Determination of Equilibrium Properties", ch. 20, pp. 589-622, Handbook of Size Exclusion Chromatography and Related Techniques", 2 nd Ed., Chi-san Wu, Ed., Marcel Dekker, 2003.

5. G. A. Sorci; W. F. Reed, "Effect of ion type and valence on polyelectrolyte conformations and interactions", Macromolecules 2004, 37, 554-565.

6. N. Sahiner, A. M. Alb, R. Graves, T. Mandal, G. L. McPherson, W. F. Reed, V. T. John, "Core-shell nanohydrogels structures as tunable delivery system", Polymer 2007, 48, 704-711.

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