Effect of large amplitude oscillatory shear (LAOS) on the dielectric response of 1,4-cis-polyisoprene》.pdf

Polymer 47 (2006) 7282e7288 /locate/polymer Effect of large amplitude oscillatory shear (LAOS) on the dielectric response of 1,4-cis-polyisoprene S. Hofl a, F. Kremer b, H.W. Spiess a, M. Wilhelm a,c,*,1, S. Kahle a,* ¨ a Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany b Universita¨t Leipzig, Institut fu¨r Experimentelle Physik I, Linne´str. 5, 04103 Leipzig, Germany c Technische Universita¨t Darmstadt, Institut fu¨r Maschinenbau, Hochschulstr. 1, 64289 Darmstadt, Germany Received 10 February 2006; received in revised form 20 March 2006; accepted 24 March 2006 Available online 7 July 2006 Abstract The dielectric response of 1,4-cis-polyisoprene under applied mechanical oscillatory shear with various shear amplitudes was investigated. For this purpose, a special setup was constructed which enables to measure dielectric spectra under the influence of large amplitude oscillatory shear (LAOS); the setup is explained in detail. A strong influence of the shear amplitude on the dielectric relaxation strength was observed if the dielectric normal mode was mechanically affected. With increasing amplitude the relaxation strength decreased while the mean relaxation time, the width and asymmetry basically remained unchanged. We interpret this process as an orientational phenomenon of the end-to-end-vectors which results in a decreasing fluctuation amplitude of the polarization fluctuations. 2006 Elsevier Ltd. All rights re