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

Abstract

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 T NI and the mechanical stress σ 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.