Polymer-Anionic Surfactants Interactions: Effects on Microstructure and Rheology Bingquan Li Center for Particulate & Surfactant Systems IAB Meeting Columbia University, NY August

Introduction Understand and determine the relation of such interactions with different surfactant head groups, and Study the effect on properties of practical importance, e.g. rheology Cationic Polymers: Thickening, conditioning… Mixture of Anionic Surfactants: Cleansing, foaming… Competitive or one dominant interactions? Objective Microstructure? Properties?

Materials Cationic polymer Jaguar c-14 (MW 300k) pH 10 (surfactants fully ionized) l 25 O C l Mixture at 1:1 mole ratio Experimental conditions Anionic surfactants l Sodium laurate l Sodium dodecyl sulfate

Structure and Properties of Complex Investigated Phase change Turbidity Size of complex Light scattering Surface activity Surface tension Charge of complex Zeta potential Polarity of complex Fluorescence Effect on the Rheology

Laurate SDS Mixture Polymer 0.1% pH O C Size of Polymer-Surfactant Complex Increased complex size suggests stronger binding between SDS and polymer.

Less polarity of complex also suggests stronger binding of SDS than Laurate. Effect of SDS in the mixture is dominant. Polarity of Polymer-Surfactant Complex pyrene I 3 /I 1 solvent polarity dependent Polymer 0.1% pH O C

Shear rate 200 1/sec Polymer 0.1% Laurate 5.3% pH 10 Polymer contribution to the viscosity decreased at lower temp. Effect of Temp. Increase on the Viscosity

With Polymer Laurate Polymer 0.1% Laurate 5.3% pH 10 Shear rate 200 1/sec Target Temp. 13 O C Effect of Temp. Decrease on the Viscosity Phase changes in different form: stars vs. fibrils. Polymer surfactant complex could act as nucleates. Time dependent?

1.Measure viscosity with time when reached at 17 O C ; 2.Shear rate at 200 1/sec. Viscosity of Polymer-Laurate System with Time Time needed for the system to reached the equilibrium structure. Polymer 0.1% Laurate 5.3% pH 10

Effect of Polymer on the Time Dependent Viscosity Polymer slowed the kinetics of the system; Higher temperature, stronger the effect is. Polymer 0.1% Laurate 5.3% pH 10 Polymer free Laurate 5.3% pH 10

Summary In surfactant mixture, cationic polymer interaction with SDS is stronger than with Laurate. Phase of surfactant solution changes with temperature by forming fibrils, while by forming stars in the presence of polymer. The kinetics of the surfactant solution is slowed by the polymer, the extent of which is temperature dependent.

Investigate the interactions between polymer and surfactants at different pH. Study surfactants of different headgroups, e.g. sodium laureth sulfate. Understand polymer-surfactant mixtures interactions in the presence of zwitterionic surfactant. Future Plan Unilever Dr. Ananth Acknowledgement Thank You !