Formation of o‐Phenylenediamine Oligomers and their Self‐Assembly into One‐Dimensional Structures in Aqueous Medium

Summary: Uniform one‐dimensional (1D) structures of o‐phenylenediamine (oPD) oligomers are obtained by direct mix of AgNO₃ and oPD aqueous solutions at room temperature. The formation of the 1D structures involves two stages: (1) oxidation of oPD by AgNO₃, yielding individual oPD oligomers; and (2) self‐assembly of the oligomers, forming the 1D structures. Upon decreasing medium pH, the 1D structures can break‐apart to form individual oligomers, or vice versa. It is also found that both the concentration and molar ratio of reactants can influence the morphology of the structures thus formed.

Schematic illustration of the formation mechanism of 1D structures from oPD and AgNO₃, and energy‐dispersed spectrum of the precipitate.     

Solid‐State Scrolls from Hierarchical Self‐Assembly of T‐Shaped Rod–Coil Molecules

On a roll : Attachment of flexible coils to the middle of a rigid rod generates T‐shaped rod–coil molecules that self‐assemble into layers that roll up to form filled cylindrical and hollow tubular scrolls, depending on the coil length, in the solid state (see picture); the rods are arranged parallel to the layer plane.

     

Controlling Aqueous Self‐Assembly Mechanisms by Hydrophobic Interactions

We report an innovative template‐assisted synthetic protocol for the selective functionalization of terminal triple bonds in oligophenyleneethynylenes (OPE) by pre‐organization in aqueous solution. By this approach, three new OPE‐based bolaamphiphiles substituted with hydrophilic poly(2‐ethyl‐2‐oxazoline) (PEtOx) chains of different length have been synthesized. The chain length was observed to strongly influence the aqueous supramolecular polymerization: bolaamphiphiles with longer hydrophilic chains aggregate into spherical nanoparticles in a stepwise fashion, whereas 2D anisotropic platelets are formed cooperatively if shorter PEtOx chains are used. Our results demonstrate that hydrophobic interactions can be strong enough to trigger cooperative effects in aqueous self‐assembly processes.     

Drug Conjugation to Cyclic Peptide–Polymer Self‐Assembling Nanotubes

We show for the first time how polymeric nanotubes (NTs) based on self‐assembled conjugates of polymers and cyclic peptides can be used as an efficient drug carrier. RAPTA‐C, a ruthenium‐based anticancer drug, was conjugated to a statistical co‐polymer based on poly(2‐hydroxyethyl acrylate) (pHEA) and poly(2‐chloroethyl methacrylate) (pCEMA), which formed the shell of the NTs. Self‐assembly into nanotubes (length 200–500 nm) led to structures exhibiting high activity against cancer cells.     

Self‐Assembly and Disassembly of Vesicles as Controlled by Anion–π Interactions

Anion–π interactions have been widely studied as new noncovalent driving forces in supramolecular chemistry. However, self‐assembly induced by anion–π interactions is still largely unexplored. Herein we report the formation of supramolecular amphiphiles through anion–π interactions, and the subsequent formation of self‐assembled vesicles in water. With the π receptor 1 as the host and anionic amphiphiles, such as sodium dodecylsulfate (SDS), sodium laurate (SLA), and sodium methyl dodecylphosphonate (SDP), as guests, the sequential formation of host–guest supramolecular amphiphiles and self‐assembled vesicles was demonstrated by SEM, TEM, DLS, and XRD techniques. The intrinsic anion–π interactions between 1 and the anionic amphiphiles were confirmed by crystal diffraction, HRMS analysis, and DFT calculations. Furthermore, the controlled disassembly of the vesicles was promoted by competing anions, such as NO₃^?, Cl^?, and Br^?, or by changing the pH value of the medium.     

Self‐Assembly of Polyaniline/Au Composites: From Nanotubes to Nanofibers

Summary: Polyaniline (PANI)/Au composite nanotubes and nanofibers are synthesized through a self‐assembly process in the presence of camphorsulfonic acid and hydrochloric acid, as dopants, respectively. The PANI/Au composites are characterized by FT‐IR, UV‐vis, and thermogravimetric analysis to verify the incorporation of the Au nanoparticles and determine the Au content. Structural characterization is performed using SEM, TEM and X‐ray diffraction. The presence of the Au nanoparticles results in an increased conductivity and improved crystallinity of the PANI. The self‐assembly method employed here is a simple and inexpensive route to synthesize multifunctional nanotubes and nanofibers and could be extended to prepare other inorganic nanoparticle/PANI composites.

TEM image of PANI/Au nanotubes.     

Cluster‐Based Self‐Assembly Route toward MoO3 Single‐Walled Nanotubes

MoO₃ has a unique rigid double‐layer structure, which makes it a real challenge to prepare nanotubular structures. The controlled synthesis of MoO₃ single‐walled nanotubes (SWNTs) is achieved through a cluster‐based self‐assembly route on the dodecanethiol/water interface. Various factors are studied at length, including precursor type, reaction time, temperature, pH value, and their influence on the morphology of products. The concept of “self‐assembly—from simple clusters to nanostructures” is proposed here based on preliminary results from the synthesis of MoO₃ SWNTs, which provides a new aspect for traditional synthetic chemistry of nanomaterials and polyoxometalates.     

Dendronized Triangular Oligo(phenylene ethynylene) Amphiphiles: Nanofibrillar Self‐Assembly and Dye Encapsulation

Triangular‐shaped oligo(phenylene ethynylene) amphiphiles 1 a and 1 b decorated in their periphery with two‐ and four‐branched hydrophilic triethyleneglycol dendron wedges, have been synthesized and their self‐assembling properties in solution and onto surfaces investigated. The steric demand produced by the dendritic substituents induces a face‐to‐face rotated π stacking of the aromatic moieties. Studies on the concentration and temperature dependence confirm this mechanism and provide binding constants of 1.2×10⁵ and 1.7×10⁵ M ^?1 in acetonitrile for 1 a and 1 b , respectively. Dynamic and static light scattering measurements complement the study of the self‐assembly in solution and demonstrate the formation of rod‐like supramolecular structures in aqueous solution. The nanofibers formed in solution can be efficiently transferred onto surfaces. Thus, TEM images reveal the presence of strands of various thickness, with the most common being several micrometers long and with diameters of around 70 nm. Some of these nanofibers present folded edges that are indicative of their ribbon‐like nature. Interestingly, compound 1 b can also form thick filaments with a rope‐like appearance, which points to a chiral arrangement of the fibers. AFM images under highly diluted conditions also reveal long fibers with height profiles that fit well with the molecular dimensions calculated for both amphiphiles. Finally, we have demonstrated the intercalation of the hydrophobic dye Disperse Orange 3 within the filaments and its subsequent release upon increasing the temperature.     

Self‐Assembly of Amphiphilic Nanocrystals

Amphiphilic hybrid materials are formed from polymer‐coated semiconductor nanoparticles that simulate a surfactant‐like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.

     

Controllable Peptide–Dendron Self‐Assembly: Interconversion of Nanotubes and Fibrillar Nanostructures

Roll up : A peptide–dendron hybrid (PDH) is capable of self‐assembling into either a soluble nanotube or an amyloid‐like fibrillar network. The structures interconvert on adjusting the salt concentration or pH value. Their hydrophobic interfaces efficiently encapsulate hydrophobic molecules in water which can then be released by lowering the pH value.

     

Cover Picture: Solid‐State Scrolls from Hierarchical Self‐Assembly of T‐Shaped Rod–Coil Molecules (Angew. Chem. Int. Ed. 9/2009)

Solid scrolls are reversibly formed by self‐assembly of rod‐shaped molecules with laterally attached coil units, in contrast to the layered structures formed from self‐assembly of planar molecules. As described by M. Lee and co‐workers in their Communication on page 1664 ff., the core structure of the scrolls, which are either filled cylinders or hollow tubes, can be controlled by variation of the length of the coil unit. The cover picture shows aligned tubular scrolls displaying well‐defined in‐plane ordering of the rod segments.

     

Engineering Hierarchical Nanostructures by Elastocapillary Self‐Assembly

Surfaces coated with nanoscale filaments such as silicon nanowires and carbon nanotubes are potentially compelling for high‐performance battery and capacitor electrodes, photovoltaics, electrical interconnects, substrates for engineered cell growth, dry adhesives, and other smart materials. However, many of these applications require a wet environment or involve wet processing during their synthesis. The capillary forces introduced by these wet environments can lead to undesirable aggregation of nanoscale filaments, but control of capillary forces can enable manipulation of the filaments into discrete aggregates and novel hierarchical structures. Recent studies suggest that the elastocapillary self‐assembly of nanofilaments can be a versatile and scalable means to build complex and robust surface architectures. To enable a wider understanding and use of elastocapillary self‐assembly as a fabrication technology, we give an overview of the underlying fundamentals and classify typical implementations and surface designs for nanowires, nanotubes, and nanopillars made from a wide variety of materials. Finally, we discuss exemplary applications and future opportunities to realize new engineered surfaces by the elastocapillary self‐assembly of nanofilaments.     

Reversible Scrolling of Two‐Dimensional Sheets from the Self‐Assembly of Laterally Grafted Amphiphilic Rods

Deep‐water scrolls: It is demonstrated that amphiphilic rods containing lateral flexible chains self‐assemble into two‐dimensional sheets in aqueous solution (see picture). Remarkably, the sheets roll up reversibly into tubular scrolls upon heating, as confirmed by cryo‐transmission electron microscopy and fluorescence microscopy.