1991
DOI: 10.1002/macp.1991.021920522
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Nematic elastomers: The influence of external mechanical stress on the liquid‐crystalline phase behavior

Abstract: As a result of an error in the evaluation programme, the values represented in Figs. 5, 6, 7 and 8 for the birefringence and mechanical stress are not correct. The correct values of the measurements are represented in the new Figs. 5 , 6, 7 and 8.The new Fig. 5 shows the plot of birefringence against the applied stress for different temperatures. The theory of Kuhn and Grun predicts for conventional rubbers a linear relation between birefringence and stress. There is no deviation from this linearity until th… Show more

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Cited by 9 publications
(6 citation statements)
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“…Stress-optical measurements on SG-LCP networks have proved successful in detecting the dramatic increase in the ratio of the birefringence to the stress that is expected as T -* T"i. 18 Here we present the first results of flow birefringence measurements on SG-LCP melts (Figure 5). These show that the stress-optic ratio in the isotropic phase rises dramatically as the material is cooled toward the transition.…”
Section: Discussionmentioning
confidence: 92%
See 1 more Smart Citation
“…Stress-optical measurements on SG-LCP networks have proved successful in detecting the dramatic increase in the ratio of the birefringence to the stress that is expected as T -* T"i. 18 Here we present the first results of flow birefringence measurements on SG-LCP melts (Figure 5). These show that the stress-optic ratio in the isotropic phase rises dramatically as the material is cooled toward the transition.…”
Section: Discussionmentioning
confidence: 92%
“…The ratio of birefringence to stress (the stress-optic ratio) has been found to increase strongly with approach to the isotropic-nematic transition of lyotropic rodlike LCPs20 and of SG-LCP elastomers. 18 Here we characterize the behavior of the stress-optic ratio as a function of temperature and shear frequency in the isotropic phase of the present SG-LCP.…”
Section: Introductionmentioning
confidence: 99%
“…been evidenced by the qualitative agreement of the curve shapes of L(T) (or those in the strain unit) and Q(T). 1,16,20,32 This is reasonable because Q is an index of the degree of local chain anisotropy. 1 This discussion also applies to the polydomain LCE because the local state within each nematic domain is qualitatively identical.…”
Section: ■ Results and Discussionmentioning
confidence: 99%
“…Q is generally T -dependent, increasing rapidly from zero as the T drops below T NI followed by a slower rate of increase. In the case of low-molecular-weight nematic liquid crystals, this behavior is described by a first-order phase transition, and the temperature response near the phase transition is described by the Landau–de Gennes model. , The detailed shape of the Q ( T ) curve is nontrivial, where the transition in LCEs is known to be blurred by crosslinking and becomes a critical or supercritical transition. In the case of azobenzene-based LCEs, the photomechanical response is believed to originate from the shift of Q ( T ) along the T axis, which corresponds to the shift of T NI . Indeed, supporting experimental results based on the T -dependent length have also been reported. , These studies suggest that understanding and controlling the Q ( T ) curve and its change in response to light are critical for tuning and optimizing the photomechanical responses of LCEs, such as the generated stress and strain, for soft-actuator applications.…”
Section: Introductionmentioning
confidence: 99%
“…In conventional liquid crystals, the N–I transition is strictly first order due to the underlying quadrupolar symmetry of the emerging phase, with the discontinuity in the orientational order parameter Q at the thermodynamically equilibrium transition point. In contrast, several experiments with LCEs show a smooth, continuous transition as a function of temperature, T . Some qualitative explanations for this smooth (continuous) transition have been proposed by extending the phenomenological Landau–de Gennes model.…”
Section: Introductionmentioning
confidence: 84%