Influence of alkyl substitution on the supramolecular organization of thiophene- and dioxine-based oligomers

Abstract

The interplay between the molecular structure, position and type of alkyl substituents on morphology and molecular packing is essential for the development of high-performance solution-processable organic semiconductors. This study focuses on the influence of the position and geometry of alkyl side chains on the supramolecular organization of thiophene-and dioxine-based oligomers. The structural investigation is performed by X-ray scattering for bulk and thin film samples. It is shown that attaching the side chains at the lateral position of the rigid oligomers mainly results in the formation of onedimensional stacks. On the other hand, terminal alkyl substitution increases the steric hindrance between side chains and reduces the molecular interactions lowering the sample crystallinity.

The Effect of Alkyl Substitution of Novel Imines on Their Supramolecular Organization, towards Photovoltaic Applications

“…In the case of thin-film examination, a presence of π -stacking peak indicates a highly ordered structure. In ordered structures, with few peaks visible, more planar molecules might be characterized by a (100) peak position—higher d -spacing values show higher macromolecule planarity [ 25 , 26 ]. After the assignment of Miller indexes, it has been noticed that both carbazole-consisting imines ( PAz-Carb ) have shown only a peak corresponding to the a parameter, connected to the short polymer axis, and thus with the planarity of macromolecules.…”

“…This clearly suggests the larger dimension in this axis, which suggests the enhanced planarity of this imine in respect to its counterpart substituted solely with octyloxy side chains. According to [ 25 , 26 ], spin-coated thin films exhibits lower order than solid samples, especially for high molar masses of macromolecules.…”

“…X-Ray diffraction studies have been performed using the D8 Advance diffractometer (Bruker, Karlsruhe, Germany) with Cu-Kα cathode (λ = 1.54 Å). Due to the critical angle for conjugated polymers using copper radiation being ~0.17° [ 25 , 26 ] and the layer thickness of sample (~100 nm), for 2D-GIWAXS setup, the 0.18° incidence angle has been applied, which is just above the critical angle for polymer layer and below the critical angle for glass support material. The scan rate has been 0.6°/min with scanning step 0.02° in range of 2.0° to 60° 2Θ (dwell time 2 s).…”

“…All WAXD (XRD) measurements acquired at the different Phi angle have been accumulated to obtain the representative pattern, then obtained profiles have been smoothed, using a 5-point, quadratic polynomial, the Savitzky–Golay smoothing filter. For the structural analysis, the unit cell parameter a is related to the short macromolecule axis (correlated to the planarity and side chains) and c corresponds to the long axis of polymer (the length of macromolecule), while b is related to the π-stacking period [ 25 ].…”

Structure–Property Relationships in Bithiophenes with Hydrogen‐Bonded Substituents

“…These serve both as solubilizing agents and to direct structure formation, guiding crystallization and molecular orientation in the solid state [8–14] . When terminal α,ω‐dialkyl substituents are introduced into calamitic (rod‐like) π‐conjugated compounds, the molecules typically organize into layered‐herringbone (LHB) structures, which are known to result in favorable two‐dimensional charge‐transport pathways [15] . This particular packing motif is observed in many prototypical high‐performance organic semiconductor materials based, for example, on pentacene [16] or benzothieno[3,2‐ b ][1]benzothiophene (BTBT) cores, [14, 17] among others [18–20] …”