Triple-shape properties of a thermoresponsive poly(ester urethane)

Thermo-mechanical investigations on a segmented poly(ester urethane) have shown that the material displays triple-shape functionality: gradual heating of programmed specimens leads first to the transformation from shape (A) to shape (B) and later from shape (B) back to permanent shape (C). In the essential two-step programming process, the first deformation state (B) is stabilized by crystallized soft segments at T < T c , the second one (A) through the polymer’s glassy state at T < T g . The transition temperatures, as analyzed for the permanent-shaped polymer via DSC, are T g ≈−49 °C and T m (onset)≈34 °C; the material crystallizes when cooled at T c (onset)≈4 °C. For the characterization of the material’s cyclic thermo-mechanical triple-shape properties, maximum deformations of ε m1 = 100% for shape (B) and ε m2 = 130% for shape (A) were tested. In cycles N = 2–5 averaged shape fixing abilities of 74% (shape A, −60 °C), 109% (shape B, 23 °C) and shape recoverabilities of 103% (A B) and 96% (B C) could be detected. Values larger than 100% indicate the occurrence of plastic deformation during the second stretching.