The effect of steam on chemical structure and mechanical properties of renewable poly(ether-block-amide)s (PEBAs) is investigated by different characterization techniques, i.e. FT-IR, TGA, DSC, DMA, and BES. Steam sterilization is a mandatory process for materials used in medical applications. This process, employed during clinical practice and replicated in this study, affects polymer structure and morphology. Steam induces an increase of polyamide (PA) crystallinity in PEBAs with a majority of PA domains, due to the conformational transition from -helix to parallel and anti-parallel -sheet, with stronger hydrogen bonding. In PEBAs with longer polyether (PE) blocks, steam induces an increase of random PA domains and the formation of a more extended hydrogen bonding network between ether and amide moieties of the two segments. As a consequence of these microdomain conformational variations, relevant changes occur in molecular relaxations as demonstrated by DMA and BES results. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 409-418