Nanoscopic Force Sensitivity of Polydiacetylene 2D Layered Composites with Guest Molecules

Abstract

Abstract2D polydiacetylene (PDA) layered composites with added guest molecules have demonstrated an excellent tunable mechanochromic properties toward the development of mechanochromic force sensors in energy‐related and medical applications. However, its force sensitivity at the nanoscale is left uncharacterized due to a lack of technique to conveniently apply forces to the 2D films in different directions, limiting the quantitative understanding of the sensitivity‐tuning mechanism. In this work, the quantitative friction force microscopy combined with fluorescence microscopy is introduced to measure the force sensitivity of the PDA layered composites with guest organic amines at the nanoscale. Intercalating nonylamine and 1‐aminodecane increase the sensitivity of 10,12‐pentacosadiynoic acid by 127% and 111%, respectively, whereas adding n‐tridecaylamine and stearylamine reduce it by 77% and 86%. This force sensitivity at the nanoscale is inversely correlated to the thermochromic temperature and the Young's moduli of the films, suggesting that the softer film has both higher force‐ and thermo‐sensitivity.