AbstractBlock oligomers of general formula CH3(CH2)nO[CH2CH2O]9(CH2)nCH3wheren= 0 to 25 have been prepared. All blocks are monodisperse. Examination of their crystallinity (by differential scanning calorimetry, X‐ray scattering, infra‐red and Raman spectroscopy) shows that, within defined limits (n>9, crystallisation temperature high), the block oligomers can crystallise completely. A likely structure is 7/2 helical monoclinic oxyethylene blocks and planar zigzag low density methylene blocks, with the oxyethylene helices normal to the lamella end‐planes and the methylene chains t