Morphology control of segmented polyurethanes by crystallization of hard and soft segments

Segmented polyurethanes (SPUs) have been designed with controlled hard to soft segment ratios. The confinement effect of the SPU blocks is induced by phase separation of the SPU segments and has been harnessed to selectively control crystallization. Hard segment (HS) concentrations greater than 50 wt.% allowed for the study of morphological changes and mechanical properties associated with confinement of the soft segment (SS). It was observed that crystallization temperature and normalized percent crystallinity were reduced with increasing HS content, creating a largely amorphous PEG SS at ambient temperature. High temperature annealing further confined the SS because the HS had more time to crystallize, which increased confinement. Considerable insight has been gained through the manipulation and characterization of the SS and HS, in an SPU, towards the design of impact absorbing and structural materials.