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Thermoplastic segmented polyurethanes which are based on poly(tetramethylene oxide) (PTMO) soft segment, linear symmetric para-phenylene diisocyanate (pPDI), and chain extended with 1,4-butanediol (BD) are discussed. The effect of variation of the soft and hard segment molecular weights as well as the overall hard segment content on structure–property behavior is investigated. Together, atomic force microscopy (AFM) and dynamic mechanical analysis (DMA) clearly establish the presence of a unique ordered thread-like microphase separated structure that displays considerable order. This thread-like microphase structure is similar to that of the “single molecule” hard segment systems reported earlier from our laboratory [1] , [2] , [3] , [4] . In addition, small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS) and ambient temperature tensile testing results help to better define the nature of the hard and soft domains.

Segmented, nonchain extended polyurethanes and polyureas based on PTMO soft segments (SS) and hard segments (HSs) based on only single molecules of a diisocyanate were synthesized. Type and nature of the diisocyanate was systematically varied in order to analyze the effect of HS symmetry and type of linkage between the HS and SS on the structure‐property relationship of these segmented copolymers. Results showed that the increased symmetry of the diisocyanates allows a more efficient packing of the HSs which leads to a microphase‐separated structure with the crystalline hard ribbon or thread‐like domains percolated throughout the SS matrix, even with a low HS content (ca. 13 wt.%). The service window of these segmented copolymers was significantly influenced by the symmetry and type of linkage between the HS and SS. Most copolymers also showed evidence of strain hardening accented by the strain induced crystallization of the PTMO SS.

New novel segmented polyurethane and polyurea copolymers have been synthesized without chain extenders and the structure-property behavior of these systems has been investigated. It is shown that by the proper choice of diisocyanate and its symmetry, one can obtain highly microphase separated systems without chain extenders and that the materials also display useful mechanical behavior. In particular, it is shown that due to the bidentate hydrogen bonding achieved in the segmented ureas, a significant modulus “service temperature window” is also obtained. It is also verified that not only can strong microphase separation be obtained with low weight fraction hard segment content (14%) but that the hard phase, which is comprised of monodisperse “single molecule” units, also displays a percolated thread-like structure throughout the dominant soft segment material — the latter being based on ca. 1000g/mol polytetramethylene oxide.

Thermoplastic segmented polyurethane and polyurea copolymers whose monodisperse hard segments are based on only a single diisocyanate molecule are discussed. The solid-state structure-property behavior of these materials demonstrates that a proper selection of the level of symmetry and/or cohesiveness of the hard microdomains may allow elimination of the traditional requirement of chain extension to obtain melt processable segmented urethanes, and more specifically, urea copolymers with useful structural properties.