Quantitative and Anisotropic Mechanochromism of Polydiacetylene at Nanoscale

Quantitative and anisotropic mechanochromism of polydiacetylene over nanoscale distances remains unaddressed even after 50 years of extensive research. This is because its anisotropic structure on substrates necessitates the application of both vertical and lateral forces (shear forces) to characterize it, whereas atomic force microscopy, which is the usual technique used to investigate nanoscale forces, is only capable of quantifying vertical forces. In this study, we address this lacuna by utilizing quantitative friction force microscopy that measures lateral forces. Our data confirm that polydiacetylene reacts only to lateral forces, F-//, and disprove the previously claimed hypothesis that the edges of the polymer crystals exhibit higher force sensitivity than the rest of the crystal. In addition, we report a correlation between mechanochromism and thermochromism, which can be attributed to the fact that both work and heat are different means of providing the same transition energy.

Automated summary

The study utilized quantitative friction force microscopy to measure the response of polydiacetylene to lateral forces, revealing the necessity of applying shear forces to characterize it at the nanoscale. The experiment confirmed the erroneous nature of the hypothesis regarding the higher force sensitivity at the edges and discovered a correlation between mechanochromism and thermochromism.