Hydrogen bonding soft segment

Figure 5.16 Similar molecular structure and aggregate structure between SMPF and spider silk. A hydrogen-bonded hard segment and soft segment form a microphase separated microstructure with a crystalline hard domain and an amorphous soft phase. The amorphous phase and crystalline phase are partially oriented. Source [10] Reproduced with permission from the Royal Society...

The elasticity of thermoplastic polyurethane rubbers (which are also known as thermoplastic urethanes or TPUs) is a function of their morphology which comprises hard and soft phases. The hard phases consist of hydrogen bonded clusters of chain segments, which are linked by flexible chain segments that make up the soft phase. The hard blocks, which are the minor phase, exist as separate domains within a continuous matrix of the majority soft phase, as shown schematically in Fig. 25.9. 

Polyurethanes with a very high carboxyl (-C=0) content are also believed to start hydrogen bonding at the ether groups in the soft segment chain. 

Extensive dynamic mechanical property studies have been carried out on hydrogen-bonded (81) and nonhydrogen-bonded (60,82) polyurethanes. Several secondary relaxations were found in addition to the major hard- and soft-segment transitions. Molecular mechanisms could... 

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