Synthesis and characterization of an ultra-soft poly(carbonate urethane)

• Ultra-soft poly(carbonate urethane).
• SAXS data evidences a characteristic domain size of 44.88.
• In tensile set experiments strain recovery averaged 96–98%, while the strain to break exceeded 500.
• Hydrogen bonding imparts partial self-healing properties to the polymer.

A high performance, thermoplastic polyurethane elastomer was synthesized with methylene bis(4-cyclohexylisocyanate), 1,4-butanediol as a chain extender and a polycarbonate polyol containing 1,6-hexanediol and 3-methyl-1,5-pentanediol. SAXS data evidences an interdomain “center-to-center” distance of 45 Å. DSC traces evidence one glass transition temperature and weak melting region. Surprisingly, the material is ultra-soft with a Shore A hardness of 64, but does not undergo any blocking. DMA analysis reveals a low temperature secondary relaxation and the glass to rubber transition followed by a rubbery plateau. In tensile set experiments strain recovery averaged 96–98%. The PCPU exhibits partial self-healing after rupture without the addition of additives or imbedded healing agents. Self-healing is attributed to interdiffusion and hydrogen bonding mechanism, where rehealing is possible. FTIR measurements characterize hydrogen bonding.

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