The adsorbed layers of polyoxyethylene n-alkyl ether surfactants C12E4, C14E4, and C16E4 at the LEAN surface have a headgroup layer that is thin and compact (only similar to 30 vol % EAN). The headgroups do not adopt a preferred orientation and are disordered within the ethylene oxide layer. Alkyl tails contain a significant number of gauche defects indicating a high degree of conformational disorder. The thickness of the tail layer increases with increasing alkyl chain length, while the headgroup layer shows little change. Lowering the C12E4 concentration from 1 to 0.1 wt % decreases the adsorbed amount, and the headgroup layer becomes thinner and less solvated, whereas C14E4 and C16E4 adsorbed layers are unaffected by dilution over the same concentration range. The C16E4 layer thickness increases and area per molecule decreases on warming to 60 degrees C, but the adsorbed layer structures of C12E4 and C14E4 are unchanged. Both effects are attributed to surfactant solubility.