Formation of 2D spherulites in Langmuir films of amphiphilic T-shaped liquid crystals

Reuter, Sascha; Amado, Elkin; Busse, Karsten; Kraska, Martin; Stühn, Bernd; Tschierske, Carsten; Kreßler, Jörg

doi:10.1016/j.jcis.2012.01.036

Cited by 13 publications

(18 citation statements)

References 63 publications

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“…Presumably, the interplay between interface alignment due to amphiphilicity and π-aggregation as well as considerable flexibility due to the supplementary chains and, to some extent, due to torsional degrees of freedom in the oligothiophene chains enable accessibility of various phases via the LB process. Such a multitude of LB-accessible phases is also known for other complex amphiphilic dyes featuring large π-systems, flexible chains, and more than one hydrophilic anchor. ,,, The lack of such a multitude of phases, i.e., the uniformity of supramolecular structures observed for the DPPs investigated in this work, is hence attributed to the dominance of ππ interactions in the two-dimensional structures produced via the LB technique.…”

Section: Resultsmentioning

confidence: 81%

“…Such a multitude of LB-accessible phases is also known for other complex amphiphilic dyes featuring large π-systems, flexible chains, and more than one hydrophilic anchor. 36,38,42,43 The lack of such a multitude of phases, i.e., the uniformity of supramolecular structures observed for the DPPs investigated in this work, is hence attributed to the dominance of ππ interactions in the two-dimensional structures produced via the LB technique.…”

Section: ■ Introductionmentioning

confidence: 87%

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Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

et al. 2021

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In this work, we present the formation of H- and J-aggregates of amphiphilic centrosymmetric diketopyrrolopyrroles containing aliphatic or aromatic amino groups. The inherent amphiphilicity of these dyes predestines their assembly at interfaces to form ordered supramolecular structures. In this work, we employed the Langmuir–Blodgett (LB) technique to generate, manipulate, and deposit such supramolecular structures. The aforementioned amines provide an additional means to control the formation of the supramolecular assemblies. In the resulting LB films, both H- and J-aggregates of the dyes can be realized, leading to very broad absorption spectra. In contrast to many reports on H- and J-aggregates, the interactions between the symmetric diketopyrrolopyrroles are controlled via interface assembly and π-stacking and not by dipolar interactions. We show that in the case of the aliphatic, but not for the aromatic amine functionalization, the usage of an acidic subphase enables the transition from H- to J-aggregate-dominated LB films via an increase in the surface pressure during deposition.

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Section: Resultsmentioning

confidence: 81%

Section: ■ Introductionmentioning

confidence: 87%

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

et al. 2021

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“…29−31 Recently, however, Reuter and co-workers reported a 2D polycrystalline spherulite texture for a Langmuir film of a small molecule: a facial p-terphenyl derivative bearing two hexadecyl chains. 36 It has been suggested that spherulite formation occurs not only by the folding of polymer chains or polymerization but also by interactions between the hydrocarbon chains of small amphiphilic molecules. If there exists a 1D interaction between the hydrocarbon chains along the fibrils, the order in the film can be evaluated by FT-IR spectroscopy, which will be discussed later in this section.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Spherulitic Crystallization in Langmuir–Blodgett Films of the Ditetradecyldimethylammonium-Au(dmit)₂ Salt

et al. 2019

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Spherulitic crystallization in Langmuir–Blodgett (LB) films of the ditetradecyldimethylammonium-Au(dmit)2 [2C14N+Me2-Au(dmit)2] salt has been characterized by polarized light microscopy, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) analyses. Analyses by differential scanning calorimetry (DSC) for the bulk crystals indicate that annealing in the temperature range of 58–100 °C may be appropriate to improve the order in the LB film. The polarized light microscopy measurement further revealed that a spherulite structure was formed after the film was annealed at 80 °C for 60 min. FT-IR spectroscopy measurements demonstrated that the order of the principal hydrocarbon chains was improved and that the rotation of CH3 groups was hindered by the annealing. Out-of-plane XRD analyses revealed that the d-spacing of the 2C14N+Me2-Au(dmit)2 LB film changed from 3.1 to 2.5 nm upon annealing. We hypothesize that a layered structure with interdigitated hydrocarbon chains, which is equivalent to or close to that of the corresponding bulk crystal, has been realized in the LB film by annealing. We consider that two different kinds of one-dimensional (1D) interactions along the a-axis are the driving forces to realize the spherulite structure in the LB system; one is an extended 1D contact due to the pronounced interdigitation of the alkyl chains of the ammonium ion, which plays a role similar to that of the folding of chains in the lamellar structures of polymers, and the other is a 1D extended sulfur–sulfur contact between Au(dmit)2 dimer pairs. So far, spherulite formation in LB films has been reported almost exclusively for polymerized materials. Here, we demonstrate that a spherulite texture can also be formed in LB films based on nonpolymerized materials via the interdigitation of hydrocarbon chains, leading to a new well-ordered state.

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“…Thus, LB layers deposited show layer pattern. [41][42][43][44] As we reduce pH of subphase to 4. Figure 8(a) shows AFM image at bent-core molecule deposited at 20 mN m −1 with subphase pH = 4, and Figure 8(b) shows AFM image at same surface pressure but pH reduced to 2.…”

Section: Imaging With Afmmentioning

confidence: 99%

Effect of pH on the control of molecular orientation in monolayer of bent-core liquid crystal materials by Langmuir–Blodgett method

et al. 2014

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Control of molecular orientation at the substrate surface is significant to understand the surface science. Langmuir films of bent-core liquid crystals having alkyl chains at both ends were deposited on silicon substrate. Studies were carried out on air-water interface by changing pH of the subphase. On compression, molecules were arranged in stacks at high pH where as uniform monolayer was formed at lower pH. Limiting area increased at low pH, which resulted in the formation of monolayer after attaining a sustainable surface pressure. Langmuir films were transferred to silicon substrate, and atomic force microscopy images showed appropriate height profiles.

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Formation of 2D spherulites in Langmuir films of amphiphilic T-shaped liquid crystals

Cited by 13 publications

References 63 publications

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

Spherulitic Crystallization in Langmuir–Blodgett Films of the Ditetradecyldimethylammonium-Au(dmit)₂ Salt

Effect of pH on the control of molecular orientation in monolayer of bent-core liquid crystal materials by Langmuir–Blodgett method

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Formation of 2D spherulites in Langmuir films of amphiphilic T-shaped liquid crystals

Cited by 13 publications

References 63 publications

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

Spherulitic Crystallization in Langmuir–Blodgett Films of the Ditetradecyldimethylammonium-Au(dmit)2 Salt

Effect of pH on the control of molecular orientation in monolayer of bent-core liquid crystal materials by Langmuir–Blodgett method

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Spherulitic Crystallization in Langmuir–Blodgett Films of the Ditetradecyldimethylammonium-Au(dmit)₂ Salt