The supramolecular structure essentially determines the properties of organic thin films. Therefore, it is of utmost importance to understand the influence of molecular structure modifications on supramolecular structure formation. In this article, we demonstrate how to tune molecular orientations of amphiphilic 4-hydroxy thiazole derivatives by means of the Langmuir-Blodgett (LB) technique and how this depends on the length of an alkylic spacer between the thiazole chromophore and the polar anchor group. Therefore, we characterize their corresponding supramolecular structures, thermodynamic, absorption, and fluorescence properties. Particularly, the polarization-dependence of the fluorescence is analyzed to deduce molecular orientations and their possible changes after annealing, i.e., to characterize the thermodynamic stability of the individual solid state phases. Because the investigated thiazoles are amphiphilic, the different solid state phases can be formed and be controlled by means of the Langmuir-Blodgett (LB) technique. This technique also allows to deduce atomistic supramolecular structure motives of the individual solid phases and to characterize their thermodynamic stabilities. Utilizing the LB technique, we demonstrate that subtle molecular changes, like the variation in spacer length, can yield entirely different solid state phases with distinct supramolecular structures and properties.

The supramolecular structures and their constituents essentially determine the optoelectronic properties of thin films. The introduction of amphiphilicity to the constituents and interface assembly is one established technique to control supramolecular structures and resulting material properties. To yield amphiphilicity, rather hydrophobic chromophores are linked to hydrophilic head groups via flexible alkyl chains. In the present work, we investigate whether replacement of the alkyl linkers by a phenylene linker, that is, replacing an electrically isolating moiety with a potentially semiconducting one, increases the conductivity through the resulting layers. After investigating the influence of the linker on molecular properties of the 2-(4-N,N-dimethylaminophenyl)-4-hydroxy-5-nitrophenyl-1,3 thiazoles exemplarily used in this work, we produce supramolecular structures by means of the Langmuir–Blodgett (LB) technique. Atomic force microscopy (AFM) and UV–vis absorption spectroscopy reveal that thin films made from the more rigid thiazole bearing the arylic linker feature a more homogeneous and stable supramolecular structure as compared to those made from the thiazole dye containing the flexible alkylic linker. Finally, conductive AFM (cAFM) results disclose that the LB films made from the thiazole bearing the π-conjugated arylic linker are less conductive than their counterparts based on the alkylic linkers. In the latter layers, the alkylic linkers provide sufficient motional degrees of freedom to allow for supramolecular rearrangement upon electrical operation during cAFM measurements, hence yielding supramolecular structures featuring increased conductivity with successive cAFM measurements. This work highlights the importance of supramolecular structures for optoelectronic properties by presenting a case where supramolecular effects excel the property changes introduced by molecular modifications.

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Longevity of complex organic devices critically depends on the supramolecular integrity of the constituting layers and interfaces. Because the latter are soft matter, they can structurally respond to perturbation of their supramolecular structure by relaxing back to a thermodynamically favorable state. To use this response for self‐healing of optoelectronically active layers and particularly interfaces, the degraded dyes in these layers need to be exchanged with non‐degraded ones. Here, we present a dye layer interfaced between a solid surface and a dye reservoir that autonomously self‐heals after photo‐degradation of single molecules to restore its optical function. Surface sensitive in situ photothermal deflection spectroscopy reveals that this supramolecular self‐healing approach critically depends on the thermodynamic stability of the layer, the chemical change of the dye upon degradation, and the medium dissolving the degraded dye and providing the reservoir dyes. Hence, the interplay of these parameters is key to successfully using this supramolecular self‐healing approach to thin layers and interfaces in organic device for increased sustainability of organic optoelectronics and related fields.

The supramolecular structure essentially determines the properties of organic thin films. In this work, we systematically investigate the influence of the chromophore on the supramolecular structure formation at air–water interfaces by means of the Langmuir–Blodgett technique. Therefore, we focus on the recently introduced class of double-anchor T-shaped amphiphilic dyes, namely, 4-hydroxy-thiazole chromophores that are centrally equipped with an amphiphilicity-inducing hexanoic acid. The thiazoles contain hydrophilic subphase-anchor groups in the 2-position (4-N,N-dimethylaminophenyl (Am), 2-pyridyl (Py), and 4-nitrophenyl (Ni)), whereas the chromophores are systematically extended in the 5-position with various substituents. The combination of the Langmuir technique with online fluorescence measurements revealed that the π–π interactions that are pronounced in the case of 4-methoxybiphenyl derivatives yield the most distinct supramolecular structures. Whereas in the case of Py and Ni derivatives ordered J-type supramolecular structures in microdomains are formed, the Am derivative forms ordered supramolecular structures that are more homogeneous, which are, however, not stabilized by J-type dipolar interactions. Because of the synergetic π–π and dipolar stabilizations, the Ni derivative bearing the 4-methoxybiphenyl unit forms exceptionally stable quasi-two-dimensional Langmuir monolayers reaching very high surface pressures beyond 60 mN/m without any sign of disturbance of the Langmuir monolayer.

Equipping a thiazole dye with push and pull moieties adds dipolar intermolecular interactions and two hydrophilic anchors to a centrally anchored π-stacking and otherwise mono-amphiphilic dye.

Linear dyes are molecular mimics of dipole antennas that receive UV–vis light. In this work the assembly of linear dyes via the Langmuir technique to achieve uniform dye alignment for optically anisotropic molecular dipole antenna arrays is presented. The molecular orientations in these arrays are quantified from Langmuir isotherms, topography data, and from polarization‐ and angle‐dependent UV–vis transmission spectra. It is achieved the smallest angles by which the transition dipole moment orientation deviates from vertical alignment (16°–30°) in the antenna arrays that have been reported in literature so far. The resulting maximum absorption contrast between grazing and vertical incidence amounts to 75%. This high optical anisotropy enables application as anisotropic receiver arrays in optical communication, as optical layers for privacy applications, or other applications building on dichroic dye layers.

Thin functional layers on surfaces or interfaces determine their function when integrated into systems and devices. Such functional layers are synthesized frequently via self-assembly of molecular monolayers (SAMs). To study...