Chemical and supermolecular structures occurring in linear polyurethanes were presented and they were referred to the analysis of the reactions connected with the step-growth polyaddition process of diisocyanates and polyols. Based on the general kinetic model of the step-growth polyaddition process, which is available in papers, inclusive of our own reports published on that subject, and based on experimental verification of that model by GPC chromatography and MALDI-ToF spectrometry. the influence was discussed of reactivity specifications of the diisocyanate and polyol monomers. and of intermediate products (urethane oligomers), on the size of molecules and on molecular weight distribution in linear polyurethane products. The applicability of such research methods as SAXS, SEM, AFM and DSC for the analysis of phase structures and micro-phase separation in the linear polyurethanes was presented. Also, the influence of phase separation on thermal and mechanical properties of the polyurethane products was addressed. Special attention was paid to the influence of polarity of polyurethane chemical structures, dispersion interactions, hydrogen bonding and ionic interactions on the value of free Surface energy of polyurethane anionomers and cationomers. The effects on chemical and biological stability of those products were considered, too. Derived from the above analysis, the latest trends were provided for the applications of linear polyurethanes: as liquid crystalline materials, urethane-acrylic and polyurethane-siloxane copolymers in electronics, medicine and civil engineering, and as environmentally friendly elastomers in protective coatings produced from waterborne polyurethane dispersions. (c) 2006 Elsevier Ltd. All rights reserved.