How the soft segment arrangement influences the microphase separation kinetics and mechanical properties of polyurethane block polymers

Abstract

In this work, morphological, phase transitions, microphase separation, hydrogen bonding, rheological and mechanical properties of novel thermoplastic polyurethane elastomers (TPUs) consisting of polytetrahydrofuran/ polycaprolactone (PTHF/PCL) as soft segments with different soft segment arrangements were discussed. Change in sequence of feeding as a reliable method for controlling soft segment arrangements was developed. Successful synthesizing of the TPUs was evaluated by ATR-FTIR and 13C NMR spectroscopy. AFM images indicated that the change in soft segment arrangements of TPUs with same molar ratio of ingredients led to different hard segment aggregations morphology. Time sweep experiment showed that the storage modulus evolution at 125 °C is different with 140 °C, and kinetics and extent of microphase separation was systematically found to reduce with increasing temperature. Isothermal and non-isothermal examinations have shown that using PCL and PTHF in the main chain accelerates the microphase separation process comparing sample with blend of polyurethanes containing one type of polyols. Mechanical property data indicated that the extreme enhanced elongation at break and toughness of TPU with random soft segment arrangements of PTHF/PCL is highest in comparison with other samples.