Quantitative and high-resolution mechanical pressure sensing functions of mechanochromic fluorenylidene-acridane†
In the field of mechanochromic materials that respond to external stimulation, although observation of mechanochromism is an essential effort, numerical data almost have not been obtained. The quantitative mechanical pressure sensing properties of mechanochromic fluorenylidene-acridane films were investigated using nanoimprinting, diffuse reflectance UV-vis spectroscopy, and Kelvin force microscopy. A linear mechanical pressure response and high spatial resolution as fine as 50 nm were observed, demonstrating the feasibility of applying fluorenylidene-acridane films in mechanical pressure measurements. Computational studies of the color change mechanisms indicate a change to a blue twisted conformer with disassembly and a return to a yellow folded conformer with assembly. An instant color change back to yellow upon contact with ethanol was demonstrated using a polyvinyl alcohol sheet and molded plastics containing fluorenylidene-acridane.