Lipids when dissolved in water have been shown to self-assemble and form a broad spectrum of complex microstructures which include isotropic micellar and microemulsion phases and liquid crystalline lamellar, hexagonal, and bicontinuous cubic phases. The phase behavior of the monoolein-water system as a function of a polymerizable monomer (acrylamide) and an oil (dodecane) was studied. It is found that with increasing acrylamide concentration, the cubic phases of monoolein are destabilized and replaced by the lamellar phase. This effect was then reversed by adding dodecane to the system. The observed behavior is explained using the surfactant parameter alpha = v/al. It is found that acrylamide interacts with the monoolein head group and increases the head group area a (smaller alpha), while dodecane partitions between the hydrophobic tails and increases the values of v/l and alpha, thus reversing the effects of acrylamide.