Robust Stretchable Thermoplastic Polyurethanes with Long Soft Segments and Steric Semisymmetric Hard Segments

Abstract

Thermoplastic polyurethane (TPU) elastomers based on polyoxytetramethylene glycol (PTMG) with 2000 g·mol–1 as soft segments (SSs) and isocyanates as well as their reaction with butanediol as hard segments (HSs) were synthesized. The three-dimensional supramolecular networks were constructed in TPU by the formation of physical HSs-rich domains via microphase separation, hydrogen bonding, and microcrystallization, which are dominated by the chemical structure of HSs. The robust stretchable TPU with an excellent tensile strength of 32 MPa and elongation of 1378% at break could be successfully prepared, and no crystallization happened to keep the elasticity even at a low temperature (−90 °C) when the steric semisymmetric bis­(4-isocyanatocyclohexyl)­methane (HMDI) was introduced into HSs-rich domains. The crystallinity and ordered hydrogen bonding content decreased in HSs-rich domains with increases in steric hindrance and asymmetry of diisocyanates. A new approach was developed to construct the high-performance TPUs by introducing long PTMG SSs for the flexibility and elasticity and steric semisymmetric HMDI hard segments.

Mechano-responsive hydrogen-bonding array of thermoplastic polyurethane elastomer captures both strength and self-healing

“…On the contrary, the FT-IR spectrum of C-IP-SS shows four bands associated with carbonyl (C = O) groups (Fig. 4a ); free (non-H-bonded) carbonyl groups of hard and soft segments (1741 cm −1 ), H-bonded carbonyl groups between hard and soft segments (1718 cm −1 ), and H-bonded carbonyl groups between hard segments (1692 cm −1 ) 55 , 56 . The shoulder peak at a lower frequency (1645 cm −1 ) corresponds to sterically hindered ester carbonyl groups that neighbor SS units 57 .…”

Green Synthesis of Waterborne Polyurethane for High Damping Capacity

“…In this work, isophorone diisocyanate (IPDI) was chosen as the hard segment in a PU chain, which can supply a large number of hydrogen bonds, provide sufficient mobility of chain segments, and maintain excellent mechanical properties. [ 23,43 ] Poly (tetramethylene oxide glycol) (PTMG) was introduced as a flexible polyol. The addition of polyether modified polydimethylsiloxane (PDMS) improves the hydrophobic properties of PU and reduces the damping temperature of PU.…”

“…The elastic modulus increases from 8.8 to 133.3 MPa and the strength also increases from 1.1 MPa to 4.7 MPa, owing to the fact that the hard segments create physically cross‐linking domains by forming hydrogen bonds. [ 43 ]…”

Mechano-responsive hydrogen-bonding array of thermoplastic polyurethane elastomer captures both strength and self-healing

“…On the contrary, the FT-IR spectrum of C-IP-SS shows four different bands associated with carbonyl (C = O) groups that are assigned to ester groups that neighbor SS units (1645 cm − 1 ), those that are not Hbonded or are in disordered soft segments (1741 cm − 1 ), are involved in H-bonding between hard and soft segments (1718 cm − 1 ), and H-bonded between hard segments (1692 cm − 1 ) ( Fig. 3a) 51,52 . As a result, the band at 1718 cm − 1 due to H-bonding between hard and soft segments is as strong as the band at 1692 cm − 1 associated with H-bonding between hard segments.…”