Thermochromic Compounds For High Strain Experiments

Stimuli-responsive molecules have recently emerged as ideal sensors to visualize and map the magnitude and location of stress in polymer materials subjected to high-strain rates. Because most of the effective stimuli-responsive molecules used as sensors, such as spiropyrans, suffer from intrinsic limitations – simultaneous activation by heat, light and mechanical stress, and low stability in the highly colored form – we seek to develop a stimuli-responsive system based on new thermo- and photochromic materials recently developed in our laboratory, called donor-acceptor Stenhouse adducts (DASA). Herein we focus on synthesizing other DASAs with varying electronic properties at both the amine donor group and the acceptor group with the goal of affecting the amount of energy required to activate the small molecules and modifying the absorbance wavelength of the adducts. By integrating multiple DASAs into the same polymer system, regions of higher and lower stress can potentially be observed. This will have a significant impact on our ability to understand how polymers fail when exposed to high-strain rates; information that will be critical in the design of new polymers.