Influence of Electrostatic Interactions on the Release of Charged Molecules from Lipid Cubic Phases

The release of positive, negative, and neutral hydrophilic drugs from pH responsive bicontinuous cubic phases was investigated under varying conditions of electrostatic interactions. A weak acid, linoleic acid (LA), or a weak base, pyridinylmethyl linoleate (PML), were added to the neutral monolinolein (ML) in order to form lyotropic liquid-crystalline (LLC) phases, which are negatively charged at neutral pH and positively charged at acidic pH. Release studies at low ionic strength (<i>I</i> = 20 mM) and at different pH values (3 and 7) revealed that electrostatic attraction between a positive drug, proflavine (PF), and the negatively charged LLC at pH = 7 or between a negative drug, antraquinone 2-sulfonic acid sodium salt (AQ2S), and the positively charged LLC at pH = 3 did delay the release behavior, while electrostatic repulsion affects the transport properties only to some extent. Release profiles of a neutral drug, caffeine, were not affected by the surface charge type and density in the cubic LLCs. Moreover, the influence of ionic strength was also considered up to 150 mM, corresponding to a Debye length smaller than the LLC water channels radius, which showed that efficient screening of electrostatic attractions occurring within the LLC water domains results in an increased release rate. Four transport models were applied to fit the release data, providing an exhaustive, quantitative insight on the role of electrostatic interactions in transport properties from pH responsive bicontinuous cubic phases

Bent-Core Based Main-Chain Polymers Showing the Dark Conglomerate Liquid Crystal Phase

We report the synthesis and characterization of main-chain liquid-crystalline polymers via the hydrosilylation polyaddition of a divinyl terminated bent-core mesogenic monomer and tetramethyldisiloxane. Interestingly, these bent-core main-chain polymers form the “dark conglomerate” mesosphase (DC) in broad ranges of temperature. This unique chiral isotropic fluid phase induced from achiral molecules vitrifies keeping at room temperature the chiral domains characteristics of this mesophase. Furthermore, while electric fields switch the bent-core moieties at the molecular level, strong electric fields are able to change the lamellar structure of the DC to a conventional SmCP phase

Scale-up of Nanoparticle Synthesis by Flame Spray Pyrolysis: The High-Temperature Particle Residence Time

The scale-up of nanoparticle synthesis by a versatile flame aerosol technology (flame spray pyrolysis) is investigated numerically and experimentally for production of ZrO₂. A three-dimensional computational fluid dynamics model is developed accounting for combustion and particle dynamics by an Eulerian continuum approach coupled with Lagrangian description of multicomponent spray droplet atomization, transport, and evaporation. The model allows the extraction of the high-temperature particle residence time (HTPRT) that is governed by the dispersion gas to precursor liquid mass flow ratio as well as the flame enthalpy content. The HTPRT is shown to control the primary particle and agglomerate size, morphology, and even ZrO₂ crystallinity in agreement with experimental data. When the HTPRT is kept constant, the production rate for ZrO₂ nanoparticles could be scaled up from ∼100 to 500 g/h without significantly affecting product particle properties, revealing the HTPRT as a key design parameter for flame aerosol processes

Polynuclear Iron(II)–Aminotriazole Spincrossover Complexes (Polymers) In Solution

Polynuclear spincrossover (SCO) complexes prepared by the combination of [Fe­(DMF)₆]²⁺ and NH₂trz (NH₂trz = 4-amino-1,2,4-triazole) were studied (2ns^– = counterion 2-naphthalenesulfonate). It is demonstrated that these [Fe­(NH₂trz)₃]­(2ns)₂ complexes can be dissolvedcontrary to common reported experiencein <i>N</i>,<i>N</i>-dimethylformamide (DMF) and, therefore, can be conveniently processed by simple means. The resulting solutions were examined with UV/vis and X-ray absorption spectroscopy (XANES and EXAFS) as well as with small-angle X-ray scattering (SAXS). At a molar NH₂trz/Fe²⁺ ratio of 3/1, corresponding to the stoichiometric ratio of the ideal coordination compound, [Fe­(NH₂trz)₃]²⁺ in the low-spin state was found to be in equilibrium with polynuclear species in the high-spin state. The equilibrium can be shifted virtually completely to the side of low-spin Fe²⁺ by an excess of the ligand. The polymer therewith formed contains 100 or more Fe²⁺ ions and is of a pronounced rigid-rod structure, with Fe–Fe distances around 3.32 Å (in comparison to 3.94 Å of the polynuclear species in the high-spin state). Reversible spin crossover takes place in solution upon a temperature increase to around 60 °C; this process is associated with a shift in equilibrium toward species shorter than the initial polynuclear species

Squid Suckerin Biomimetic Peptides Form Amyloid-like Crystals with Robust Mechanical Properties

We present the self-assembly of fibers formed from a peptide sequence (<b>A1H1</b>) derived from suckerin proteins of squid sucker ring teeth (SRT). SRT are protein-only biopolymers with an unconventional set of physicochemical and mechanical properties including high elastic modulus coupled with thermoplastic behavior. We have identified a conserved peptide building block from suckerins that possess the ability to assemble into materials with similar mechanical properties as the native SRT. <b>A1H1</b> displays amphiphilic characteristics and self-assembles from the bottom-up into mm-scale fibers initiated by the addition of a polar aprotic solvent. <b>A1H1</b> fibers are thermally resistant up to 239 °C, coupled with an elastic modulus of ∼7.7 GPa, which can be explained by the tight packing of β-sheet-enriched crystalline building blocks as identified by wide-angle X-ray scattering (WAXS), with intersheet and interstrand distances of 5.37 and 4.38 Å, respectively. A compact packing of the peptides at their Ala-rich terminals within the fibers was confirmed from molecular dynamics simulations, and we propose a hierarchical model of fiber assembly of the mature peptide fiber

Hierarchically Structured Microfibers of “Single Stack” Perylene Bisimide and Quaterthiophene Nanowires

Organic nanowires and microfibers are excellent model systems for charge transport in organic semiconductors under nanoscopic confinement and may be relevant for future nanoelectronic devices. For this purpose, however, the preparation of well-ordered organic nanowires with uniform lateral dimensions remains a challenge to achieve. Here, we used the self-assembly of oligopeptide-substituted perylene bisimides and quaterthiophenes to obtain well-ordered nanofibrils. The individual nanofibrils were investigated by spectroscopic and imaging methods, and the preparation of hierarchically structured microfibers of aligned nanofibrils allowed for a comprehensive structural characterization on all length scales with molecular level precision. Thus, we showed that the molecular chirality resulted in supramolecular helicity, which supposedly serves to suppress lateral aggregation. We also proved that, as a result, the individual nanofibrils comprised a single stack of the π-conjugated molecules at their core. Moreover, the conformational flexibility between the hydrogen-bonded oligopeptides and the π–π stacked chromophores gave rise to synergistically enhanced strong π–π interactions and hydrogen-bonding. The result is a remarkably tight π–π stacking inside the nanofibrils, irrespective of the electronic nature of the employed chromophores, which may render them suitable nanowire models to investigate one-dimensional charge transport along defined π–π stacks of p-type or n-type semiconductors

Diyne-Functionalized Fullerene Self-Assembly for Thin Film Solid-State Polymerization

C₆₀ fullerene derivatives bearing aliphatic chains can self-assemble into versatile supramolecular structures. Cross-linking of such self-assembled morphologies is an attractive approach to enhance the structural stability of these self-organized structures. We describe the synthesis of a C₆₀ functionalized with a single alkyl chain bearing a diacetylene moiety. In a thin film, the molecule self-assembles into lamellar arrays. The character of the side chain attached to the fullerene is key to the observed packing ability. The stabilization proceeds through solid-state polymerization of the diacetylene moieties. By blending the fullerene derivative with a cyanine dye, various nanostructured fullerene morphologies are obtained that can be selectively stabilized by thermal polymerization. These films can serve as basis for nanostructured fullerene scaffolds that can find applications in optics and electronics

Hierarchically Structured Microfibers of “Single Stack” Perylene Bisimide and Quaterthiophene Nanowires

Organic nanowires and microfibers are excellent model systems for charge transport in organic semiconductors under nanoscopic confinement and may be relevant for future nanoelectronic devices. For this purpose, however, the preparation of well-ordered organic nanowires with uniform lateral dimensions remains a challenge to achieve. Here, we used the self-assembly of oligopeptide-substituted perylene bisimides and quaterthiophenes to obtain well-ordered nanofibrils. The individual nanofibrils were investigated by spectroscopic and imaging methods, and the preparation of hierarchically structured microfibers of aligned nanofibrils allowed for a comprehensive structural characterization on all length scales with molecular level precision. Thus, we showed that the molecular chirality resulted in supramolecular helicity, which supposedly serves to suppress lateral aggregation. We also proved that, as a result, the individual nanofibrils comprised a single stack of the π-conjugated molecules at their core. Moreover, the conformational flexibility between the hydrogen-bonded oligopeptides and the π–π stacked chromophores gave rise to synergistically enhanced strong π–π interactions and hydrogen-bonding. The result is a remarkably tight π–π stacking inside the nanofibrils, irrespective of the electronic nature of the employed chromophores, which may render them suitable nanowire models to investigate one-dimensional charge transport along defined π–π stacks of p-type or n-type semiconductors

Hierarchically Structured Microfibers of “Single Stack” Perylene Bisimide and Quaterthiophene Nanowires

Organic nanowires and microfibers are excellent model systems for charge transport in organic semiconductors under nanoscopic confinement and may be relevant for future nanoelectronic devices. For this purpose, however, the preparation of well-ordered organic nanowires with uniform lateral dimensions remains a challenge to achieve. Here, we used the self-assembly of oligopeptide-substituted perylene bisimides and quaterthiophenes to obtain well-ordered nanofibrils. The individual nanofibrils were investigated by spectroscopic and imaging methods, and the preparation of hierarchically structured microfibers of aligned nanofibrils allowed for a comprehensive structural characterization on all length scales with molecular level precision. Thus, we showed that the molecular chirality resulted in supramolecular helicity, which supposedly serves to suppress lateral aggregation. We also proved that, as a result, the individual nanofibrils comprised a single stack of the π-conjugated molecules at their core. Moreover, the conformational flexibility between the hydrogen-bonded oligopeptides and the π–π stacked chromophores gave rise to synergistically enhanced strong π–π interactions and hydrogen-bonding. The result is a remarkably tight π–π stacking inside the nanofibrils, irrespective of the electronic nature of the employed chromophores, which may render them suitable nanowire models to investigate one-dimensional charge transport along defined π–π stacks of p-type or n-type semiconductors

Hierarchically Structured Microfibers of “Single Stack” Perylene Bisimide and Quaterthiophene Nanowires

Organic nanowires and microfibers are excellent model systems for charge transport in organic semiconductors under nanoscopic confinement and may be relevant for future nanoelectronic devices. For this purpose, however, the preparation of well-ordered organic nanowires with uniform lateral dimensions remains a challenge to achieve. Here, we used the self-assembly of oligopeptide-substituted perylene bisimides and quaterthiophenes to obtain well-ordered nanofibrils. The individual nanofibrils were investigated by spectroscopic and imaging methods, and the preparation of hierarchically structured microfibers of aligned nanofibrils allowed for a comprehensive structural characterization on all length scales with molecular level precision. Thus, we showed that the molecular chirality resulted in supramolecular helicity, which supposedly serves to suppress lateral aggregation. We also proved that, as a result, the individual nanofibrils comprised a single stack of the π-conjugated molecules at their core. Moreover, the conformational flexibility between the hydrogen-bonded oligopeptides and the π–π stacked chromophores gave rise to synergistically enhanced strong π–π interactions and hydrogen-bonding. The result is a remarkably tight π–π stacking inside the nanofibrils, irrespective of the electronic nature of the employed chromophores, which may render them suitable nanowire models to investigate one-dimensional charge transport along defined π–π stacks of p-type or n-type semiconductors