A series of di-n-alkyl phosphate amphiphiles containing phenyl and phenoxy groups in the hydrophobic tails were synthesised, and their aggregation behaviour was investigated using fluorescence spectroscopy, differential scanning calorimetry, and cryo-electron microscopy. The aggregates displayed a wide variety of aggregate morphologies. The incorporation of a phenyl group into the end or in the middle of the alkyl chain lowered the main phase transition temperature, resulting in closed vesicles only above the phase transition temperature. Introducing a phenoxy group at the end of the alkyl chain resulted in open bilayer structures and bicelles.