Polymers are used to increase the viscosity of formulations to impart beneficial characteristics. To minimize the amount of polymer needed, polymers that form gels through aggregation of grafted hydrophobic groups are employed. These so-called associative polymers do however, interact with the other formulation components e.g. surfactants & particles. Thus, formulation can be challenging. Here, we study the interaction between two common components, a series of ethylene oxide based urethane polymers and the surfactant sodium dodecylsulphate. Competitive interactions between surfactant and hydrophobic moieties on the polymer lead to complex composition dependent behaviour. This study sets the background to two other proposals where we wish to examine the impact of added particles of varying surface composition. Together, these studies represent a detailed study into complex mixtures.