Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 32: Polymer dynamics
CPP 32.1: Vortrag
Mittwoch, 9. März 2005, 11:15–11:30, TU C130
Time resolved FTIR-Spectroscopy on Segmental Reorientation of Nematic Elastomers Under External Mechanical Fields — •Michael Tammer1, Jianjun Li1, Ansgar Komp2, Heino Finkelmann2, and Friedrich Kremer1 — 1Universität Leipzig, Institut für Experimentelle Physik I, Linnéstr. 5, 04103 Leipzig — 2Albert-Ludwigs-Universität Freiburg, Institut für Makromolekulare Chemie, Stefan Meier-Str. 31, 79104 Freiburg
Time dependent polarized Fourier Transform Infrared (FTIR) spectroscopy is employed to study the segmental orientation and mobility of liquid crystalline elastomers (LCEs) with monodomain structure in response to external mechanical fields parallel and perpendicular to the nematic director. The reorientation and order parameter of the molecular moieties referring to the backbone, the spacer molecules and the mesogens are analyzed in detail. For parallel stretching, nearly no angular excursion is observed while the order parameter as measured by the IR dichroism of the different molecular segments is changed. For strain applied perpendicular to the mesogen orientation, a threshold is found in the reorientation process which varies strongly with the network density. Under sufficient high strain the network is no longer stable, i.e. a continuous reorientation is found while the order parameter dramatically decreases.