Smectic rheology |
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| Authors: | Dr Ralph H Colby Christopher K Ober Jeffery R Gillmor Richard W Connelly Tony Duong Giancarlo Galli Michele Laus |
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| Institution: | (1) Department of Materials Science and Engineering, The Pennsylvania State University, 16802 University Park, Pennsylvania, USA;(2) Department of Materials Science and Engineering, Cornell University, 14853-1501 Ithaca, New York, USA;(3) Imaging Research and Advanced Development, Eastman Kodak Company, 14650-2109 Rochester, New York, USA;(4) Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, Via Risorgimento 35, 56100 Pisa, Italy;(5) Dipartimento di Chimica Industriale e dei Materiali, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy |
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| Abstract: | We have studied the oscillatory shear response of three thermotropic smectic-A liquid crystalline materials with no external aligning field (other than the necessary presence of rheometer plates). Two are polymers (one main-chain and one side-chain) and the other is a small molecule smectic. All three exhibit the classical linear response to oscillatory shear characteristic of a viscoelastic solid at sufficiently small strain amplitudes and frequencies. However, for strain amplitudes exceeding a small critical value, these materials exhibit a strongly nonlinear response to strain, which is characterized in detail. While the low-strain moduli and the critical strain of the three smectics are considerably different, the nonlinear response has some universal character which is presumably related to the low energy for the formation of defects in smectic liquid crystals. |
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| Keywords: | Smectic modulus strain amplitude yield stress yield strain |
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