Abstract A detailed crystallization study of the linear n ‐polyurethane ( n ‐PUR) family for n ranging from 5 to 12 was carried out by DSC supported by polarizing optical microscopy. The study embraces crystallization of all the n ‐PUR under both nonisothermal and isothermal conditions. The odd and even series of n ‐PUR defined by the parity of the number of methylenes ( n ) contained in the polymer repeating unit are considered and separately analyzed. All the members of the two series showed a thermal behavior consistent with their chemical constitution. Isothermal crystallization data were analyzed by the kinetics Avrami approach which revealed that the “crystallizability” of n ‐PUR increases steadily with the flexibility of the polyurethane chain. Melting and enthalpy temperatures of isothermally and nonisothermally crystallized n ‐PUR were found to vary with n according to a zig‐zag plot characteristic of odd–even effect. Given the structural similitude of n ‐PUR with ( n + 2)‐nylons, results were referenced to those reported for this family of polyamides. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1368–1380, 2009