Insights into the behaviour of hydrophobically modified ethoxylated urethane polymers in soft and hard colloid formulation

Hydrophobically modified ethoxylated urethane polymers (HEUR) are used as viscosity modifiers in various formulations, e.g. cosmetics, paints. The HEURS show a complex behaviour in solution owing to the interaction between the hydrophobic segments present in the polymer and other formulation components. Since HEUR containing formulations are complex and multi-component, binary mixtures of HEURs with other formulation components e.g. surfactant, particles and oil were initially examined. The study was then expanded to model ternary formulations - polymer/ sodium dodecylsulphate (SDS)/latex and polymer/SDS/oil. The main techniques used here were nuclear magnetic resonance and small-angle neutron scattering. The HEUR showed evidence of strong interaction with SDS, where the SDS interacts both with the polymer hydrophilic and hydrophobic segments. The effect of varying the HEUR architecture on the behaviour of polymer in solution and the interaction with SDS has been explored by studying three different polymers, C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10, and C18-L-(EO200-L)7-C18. It has been concluded that the linkers play an important role in the behaviour of the polymer, where the polymer that possess more linkers show higher viscosity and lower diffusion coefficient at fixed concentration. The key polymer investigated here C6-L-(EO100-L)9-C6 showed weak adsorption to a hydrophobic (polystyrene-butylacrylate) latex. Decreasing the hydrophobicity of the particles turned off the adsorption of the polymer. The addition of SDS to the polymer/latex mixture further weakened the polymer adsorption to the hydrophobic latex. It was therefore concluded that the polymer/SDS interaction was stronger than polymer/latex interaction. Finally, the three same polymers with different architectures were used to stabilise a model emulsion dodecane in water in which the oil droplets were stabilised in the polymer network. The addition of SDS to the emulsion shows a synergistic effect for the oil solubilisation. Evidence of SDS interaction with the polymer in the emulsion has been observed. This work developed insights into the interaction of the HEUR in model formulation by highlighting the key interactions and factors in the formulation