Nematic elastomers, 1. Effect of the spacer length on the mechanical coupling between network anisotropy and nematic order

Abstract

The influence of the spacer length was investigated for the correlation between the network anisotropy and the order parameter of the mesogenic units. Stress-optical measurements show that a closer coupling of the mesogenic moieties to the polymer backbone results in an increased interaction between the mechanical field and the mesogenic groups. The correlation between the phase transformation temperature TNI and the mechanical stress cr is represented using both, our experimental measurements and the derivation from the Landau-de Gennes (LDG) formulation.From our results, it is possible, for the first time, to estimate the cross-coupling coefficient U between the order parameter and the strain of a nematic elastomer. The analysis of the elastic properties of the elastomers suggests that non-linear coefficients might become important to obtain quantitative agreement between theory and experiment.CCC 0025-1 16)</91/$05.00

Thermal diffusion and bending kinetics in nematic elastomer cantilever

“…This direct coupling between physical conformation and order parameter has been theoretically predicted a long time ago [2], and then comprehensively demonstrated by simultaneous measurements of length and order using diffraction techniques [3,4,5].…”

Nematic Elastomers: The Dependence of Phase Transformation and Orientation Processes on Crosslinking Topology

“…The order parameter as derived by the Haller extrapolation is shown at the right axis of Figure 9. A shift in the phase transformation temperature with increasing stress, as observed for other elastomers, [13] cannot be observed within the experimental error of the temperature of DT = 1 K.…”

“…The correlation between the results of the stress-optical experiments and the coupling coefficient U is derived in the following part. In the paranematic phase the order parameter S is [13] …”

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