The structures of poly[oxy(N-alkylsulfonylmethyl)ethylene]s (ASE-Ns) were examined with X-ray, IR, DSC, and polarized optical microscopy. The structures of ASE-Ns were strongly dependent on the alkyl side-chain length. ASE-2 and ASE-3, the shortest ones, were amorphous materials. ASE-4 and ASE-5 showed nematic characteristics. ASE-6-ASE-12 had smectic A structures. ASE-14 and ASE-16 could be labeled as more ordered structures higher than smectic A (probably smectic B or smectic E). The d-spacings of the first small-angle reflections were double the most extended side-chain length and linearly increased with a slope of 2.50 Angstrom per methylene unit, regardless of the structural phases. The maintenance of the double-layered structure in all ASE-Ns may be due to the strong dipole-dipole interactions at both sides of the layers against the main chain for all amorphous, nematic, and smectic phases of ASE-Ns. The double-layered structure was maintained above the isotropic temperature, indicating that dipole-dipole interactions were not destroyed although the alkyl side chains melted during the isotropic transition. (C) 2004 Wiley Periodicals, Inc.