Molecular-scale shear response of the organic semiconductor β -DBDCS (100) surface

Abstract

In this work we present friction-force microscopy (FFM) lattice-resolved images acquired on the (100) facet of the semiconductor organic oligomer (2Z,2 Z) − 3,3 -(1,4-phenylene)bis(2-(4-butoxyphenyl)acrylonitrile) (β-DBDCS) crystal in water at room temperature. Stick-slip contrast, lateral contact stiffness, and friction forces are found to depend strongly on the sliding direction due to the anisotropic packing of the molecular chains forming the crystal surface along the [010] and [001] directions. The anisotropy also causes the maximum value of the normal force applicable before wearing to increase by a factor of 3 when the scan is performed along the [001] direction on the (100) face. Altogether, our results contribute to achieving a better understanding of the molecular origin of friction anisotropy on soft crystalline surfaces, which has been often hypothesized but rarely investigated in the literature.

Thermodynamics of Oiling-Out in Antisolvent Crystallization. II. Diffusion toward Spinodal Decomposition

“…The example solute, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(4-butoxyphenyl) acrylonitrile) (DBDCS), is a fluorophore exhibiting aggregation-induced emission. Its fluorescence lifetime and quantum yield increase after aggregation, 22,23 allowing for detection of fluorescent crystal nucleation and growth against a nonfluorescent background. 20,24 DBDCS is insoluble in water (the antisolvent) and slightly soluble in 1,4-dioxane (the "good" solvent, solubility 8 g/L).…”

“…The example solute, (2 Z ,2′ Z )-2,2′-(1,4-phenylene)­bis­(3-(4-butoxyphenyl) acrylonitrile) (DBDCS), is a fluorophore exhibiting aggregation-induced emission. Its fluorescence lifetime and quantum yield increase after aggregation, , allowing for detection of fluorescent crystal nucleation and growth against a nonfluorescent background. , DBDCS is insoluble in water (the antisolvent) and slightly soluble in 1,4-dioxane (the “good” solvent, solubility 8 g/L) . Two polymorphs of DBDCS have been reported to switch under shear stress: the γ phase (green emission, fluorescence lifetime >10 ns) and the β phase (blue emission, fluorescence lifetime <6 ns). , The Jouyban–Acree model , allowed us to extract thermodynamic parameters from solubility measurement.…”

Friction Force Mapping of Molecular Ordering and Mesoscopic Phase Transformations in Layered-Crystalline Organic Semiconductor Films

“…In this study, we report that the mesoscopic phase transformation can be observed and visualized by friction force microscopy (FFM), an extended technique of static-mode AFM. The FFM detects the torsional response of the AFM cantilever on the sample surface and measures the friction properties of the sample. − As friction properties have been utilized for characterizing phase behaviors in many cases of organic − and inorganic − materials, FFM has the potential for evaluating the crystalline states of OSC films. It is found in the FFM images of spin-coated films of 2-C8-BTNT that high-friction and low-friction phases are separately formed at a mesoscopic scale during annealing processes.…”

Thermodynamics of Oiling-Out in Antisolvent Crystallization. I. Extrapolation of Ternary Phase Diagram from Solubility to Instability

“…The example solute, DBDCS ((2 Z ,2′ Z )-2,2′-(1,4-phenylene)­bis­(3-(4-butoxyphenyl) acrylonitrile), Figure ), has been previously investigated in a microfluidic system. , It is insoluble in water (the nonsolvent) but slightly soluble in 1,4-dioxane (the “good” solvent). Its fluorescence depends on the molecular arrangement, , enabling further in situ characterization of the polymorphism and the phase transitions. Two polymorphs of DBDCS have been reported: the γ phase (green emission, fluorescence lifetime >10 ns) and the β phase (blue emission, fluorescence lifetime <6 ns).…”