Synergistic surfactant blends are disclosed. In one aspect, the blend comprises an anionic surfactant and a metathesis-based cationic surfactant comprising a quaternized derivative. The quaternized derivative is a quaternized fatty amine, quaternized fatty amidoamine, imidazoline quat, or esteramine quat made from a metathesis-derived C10-C17 monounsaturated acid or its ester derivative. Also disclosed are synergistic surfactant blends comprising a cationic surfactant and a metathesisbased anionic surfactant comprising a sulfonated derivative. The sulfonated derivative is a fatty ester sulfonate, fatty acid sulfonate, sulfoestolide, fatty amide sulfonate, sulfonated fatty ester alkoxylate, imidazoline quat sulfonate, sulfonated amidoamine oxide, or sulfonated amidoamine betaine. The synergistic blends have a negative value or a reduced interfacial tension (IFT) when compared with an expected IFT value calculated from the individual surfactant components. Blends of the invention also exhibit surprisingly favorable solubility profiles.
