Interplay between nematic ordering and thermomechanical response in a side-chain liquid single crystal elastomer containing pendant azomesogen units

Photoactive materials based on azobenzene derivatives exhibit interesting properties related to the reversible photo-isomerisation between the trans and cis isomers of the azo-compound. In this work we report the preparation and physical-chemical characterization of Liquid Single Crystal Elastomers (LSCEs) containing azobenzene derivative side-chain mesogens as co-monomer. The interplay between the orientational ordering and mechanical response in the nematic phase is investigated by thermomechanical measurements as well as by deuteron NMR spectroscopy. We demonstrate that local nematic order can be reliably probed in azo-LSCEs using low molar mass deuterated cyanobiphenyl nematogen in low concentrations. No phase separation of the dopant is observed. The nematoelastic coupling eav(T)∝Sav(T) between the effective sample deformation and average nematic order parameter is present over a wide temperature range even in the systems with relatively large heterogeneity of the nematic order and misaligned nematic domains.

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