Shear modulus of polydomain, mono-domain and non-mesomorphic side-chain elastomers: Influence of the nematic order |
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Authors: | P Stein N Aßfalg H Finkelmann P Martinoty |
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Institution: | (1) Laboratoire de Dynamique des Fluides Complexes, Université Louis Pasteur, 4 rue Blaise Pascal, 67070 Strasbourg Cedex, France, FR;(2) Institut für Makromoleculare Chemie, Stefan Meier Str. 31, 79104 Freiburg, Germany, DE |
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Abstract: | We investigate the behavior of the complex shear modulus of a series of elastomers including mono-domain and poly-domain liquid
crystal samples, and a non-mesomorphic sample. We find that the dynamics of the glass transition are strongly modified by
the nematic order. This result explains why the truly elastic response of liquid crystal elastomers can only be observed in
the isotropic phase at very high temperatures and at very low frequencies. Between the elastic regime and the glassy state,
the elastomers have a visco-elastic regime, which is characterized by a Rouse-like behavior for mono-domain and poly-domain
samples, and by a Zimm-like behavior for the non-mesomorphic sample. We also show that the mono-domain sample exhibits marked
anisotropy of the shear-modulus G
′. This anisotropy, which is observed for the first time, is a function of frequency and is inverted between low and high frequencies,
due to relaxation effects of the orientational order.
Received 28 January 2000 and Received in final form 16 October 2000 |
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Keywords: | PACS 83 80 Dr Elastomeric polymers – 61 30 -v Liquid crystals – 83 10 Nn Polymer dynamics |
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