TY - JOUR A1 - Frübing, P. A1 - Krüger, H. A1 - Goering, Harald A1 - Gerhard-Multhaupt, R. T1 - Relaxation behaviour of thermoplastic polyurethanes with covalently attached nitroaniline dipoles JF - Polymer N2 - Thermoplastic polyurethanes with covalently attached nitroaniline chromophores exhibit a strong high-temperature relaxation associated with a glass transition rather than the typical frequency-independent loss due to the aggregation of polymer chains via hydrogen bonds. This relaxation behaviour suggests the formation of an amorphous structure without separation into soft-segment and hard-segment phases. In such a structure, a field-induced orientation of molecular dipoles is stabilised by the high viscosity of the material below its glass transition. The dipole orientation yields a pyroelectric effect caused by dipole-density changes upon thermal expansion and contraction. The changes in phase separation are investigated by varying the chain length of the soft-phase component and studying its influence on the calorimetric, dynamic-mechanical, and dielectrical properties. Good correlation was found between differential scanning calorimetry, dynamic-mechanical analysis and dielectric spectroscopy as well as measured and calculated pyroelectric coefficients. This leads to a uniform picture of the structural changes caused by the incorporation of nitroaniline chromophores into the polyurethane structure. KW - Thermoplastic polyurethane KW - Nitroaniline chromophore KW - Dielectric relaxation PY - 2002 DO - https://doi.org/10.1016/S0032-3861(02)00075-7 SN - 0032-3861 SN - 1873-2291 VL - 43 IS - 9 SP - 2787 EP - 2794 PB - Springer CY - Berlin AN - OPUS4-2062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -