A simple and versatile method to tailor physicochemical properties of thermoplastic polyurethane elastomers by using novel mixed soft segments

Novel thermoplastic polyurethane elastomers (TPUs) were designed and synthesized using mixtures of poly (tetramethylene ether) glycol (PTMG) and polycaprolactone (PCL) diols as soft segments. Five block polyurethanes with different soft segment composition were studied in order to discover the impact of mixed soft segments on the properties of TPUs. The corresponding properties of these polyurethanes including phase transitions, morphology, microphase separation, hydrogen bonding, rheological and mechanical were investigated by experimental methods. Molecular dynamics simulation was also used to evaluate dynamic of hard and soft segments, hydrogen bonding and segmental interactions at atomic level. Successful synthesizing of the TPUs was evaluated by ATR-FTIR and 13C NMR spectroscopy. The results indicated that polyurethanes with higher PTMG content produce stronger hydrogen bonding, more solid like behavior, higher microphase separation and lower viscosity than polyurethanes with high PCL diol; however the most exciting outcome is the influence that mixed soft segments have on the microphase separation kinetics and mechanical properties. Isothermal and non-isothermal examinations have shown that using mixed soft segments accelerated the microphase separation process comparing samples with one type of polyols and sample containing equal compositions of each polyols has the fastest microphase separation kinetics. Microscopy images showed that this sample has the thread-like hard segment rich regions and its morphology differs from other samples. Mechanical property data indicated that the enhanced elongation at break and overall toughness of TPU at equal ratio of PCL/PTMG is highest in comparison with other samples.