Aliphatic flexible spacer length controls photomechanical response in compact, ordered liquid crystalline polymer networks

Publication date: 20 December 2017
Source:Polymer, Volume 133
Author(s): Amir Skandani, J. Arul Clement, Stephanie Tristram-Nagle, M. Ravi Shankar
The aliphatic spacer length connected to the rigid mesogenic cores is shown to control the structural organization and mechanical actuation in response to light-stimulus in azobenzene-functionalized liquid crystalline polymers networks. The spacer lengths in the mesogenic host (non-photochromic) and in the photo-active azobenzene-functionalized cross linker are parametrically varied to create monodomain liquid crystalline samples. A suite of thermomechanical, photomechanical and structural characterization is used to characterize the binary co-polymers. The photomechanical responses are compared by calculating a figure-of-merit – Photocompliance (Cp). This parameter, Cp, which characterizes the incremental strain generated in response to unit intensity of irradiation (W/cm²), is found to correlate strongly with the Sxray order parameter and the D-spacings. We show that compact (smaller D) and higher ordering of the mesogens that result in copolymers with longer flexible spacers manifest greater photomechanical activity.

Graphical abstract

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