Polyurethanes containing a crystalline polyol and semiflexible urethane segments

Ultradrawing semicrystalline polymers is an intriguing approach to develop stiff, strong, and tough polymeric fibers. In the research field of polyurethane copolymer elastomers the term “soft segment” usually refers to the medium molecular weight glycol while the term “hard segment” stands for the urethane rich or isocyanate‐short glycol segments. Here we investigate the influence of semiflexible segment content in the urethane rich phase on the mechanical properties and morphology of polyurethanes synthesized with a crystalline polyol as a “soft” segment. Materials with lower semiflexible urethane segment content developed stiffer and stronger materials upon drawing. This was related to greater soft segment crystallization along the draw direction. Materials with a higher fraction of semiflexible urethane segments were more elastic (higher yield strains and strengths) but exhibited more brittle‐like fracture.