AbstractInfrared spectra of monodisperse (DP ≤ 35) and polydisperse (average DP ≤ 45) oligo(ethylene glycol)s are recorded for melts and for solids over a temperature range (+70°C to ‐80°C). Spectra in the hydroxyl stretching region show that the solid monodisperse oligomers with DP ≤ 25 at temperatures well below the melting point have highly ordered lamella end surfaces with hydroxyl groups from adjacent lamellae hydrogen bonded in long chains, whereas the solid polydisperse oligomers of comparable chain length have disordered lamella end surfaces with hydroxyl‐ether as well as hydroxyl‐hydroxyl hyd