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.

     

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.

     

Multicolour Self‐Assembled Fluorene Co‐Oligomers: From Molecules to the Solid State via White‐Light‐Emitting Organogels

Five fluorene‐based co‐oligomers have been prepared to study their self‐assembly in a wide range of concentrations, from dilute solutions to the solid state. Subtle changes to the chemical structures, introduced to tune the emission colours over the entire visible range, induce strong differences in aggregation behaviour. Only two of the fluorescent co‐oligomer derivatives self‐assemble to form soluble fibrils from which fluorescent organogels emerge at higher concentrations. In contrast, the other compounds form precipitates. Mixed fluorescent co‐oligomer systems exhibit partial energy transfer, which allows the creation of white‐light‐emitting gels. Finally, a mechanism for the hierarchical self‐assembly of this class of materials is proposed based on experimental results and molecular modelling calculations.     

Gelation‐Induced Enhanced Fluorescence Emission from Organogels of Salicylanilide‐Containing Compounds Exhibiting Excited‐State Intramolecular Proton Transfer: Synthesis and Self‐Assembly

Self‐assembly structure, stability, hydrogen‐bonding interaction, and optical properties of a new class of low molecular weight organogelators (LMOGs) formed by salicylanilides 3 and 4 have been investigated by field‐emission scanning electron microscopy (FESEM), X‐ray diffraction (XRD), UV/Vis absorption and photoluminescence, as well as theoretical studies by DFT and semiempirical calculations with CI (AM1/PECI=8) methods. It was found that salicylanilides form gels in nonpolar solvents due to π‐stacking interaction complemented by the presence of both inter‐ and intramolecular hydrogen bonding. The supramolecular arrangement in these organogels predicted by XRD shows lamellar and hexagonal columnar structures for gelators 3 and 4 , respectively. Of particular interest is the observation of significant fluorescence enhancement accompanying gelation, which was ascribed to the formation of J‐aggregates and inhibition of intramolecular rotation in the gel state.     

Mesogen‐Free Supramolecular Liquid Crystalline State Formed by a Polyelectrolyte/Amphiphile Complex

Summary: The microstructure and phase transformation of a highly‐branched polyethyleneimine/octadecanoic acid (PEI(OA)_1.0) complex were investigated using a combination of DSC, XRD, optical polarised microscopy and temperature dependent FT‐IR spectroscopy. A mesogen‐free thermotropic liquid crystalline state was observed in a certain temperature region. The strong ionic interaction between  COO⁻ (from OA) and  NH (from PEI) and the hydrophobic interaction between the alkyl side chains contributes to the formation of a thermotropic liquid crystalline structure.

     

Multi‐stimuli‐responsive self‐immolative polymer assemblies

Self‐immolative polymers (SIPs) undergo depolymerization in response to the cleavage of stimuli‐responsive end‐caps from their termini. Some classes of SIPs, including polycarbamates, have depolymerization rates that depend on environmental factors such as solvent and pH. In previous work, hydrophobic SIPs have been incorporated into amphiphilic block copolymers and used to prepare nanoassemblies. However, stimuli‐responsive hydrophilic blocks have not previously been incorporated. In this work, we synthesized amphiphilic copolymers composed of a hydrophobic polycarbamate SIP block and a hydrophilic poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) block connected by a UV light‐responsive linker end‐cap. It was hypothesized that after assembly of the block copolymers into nanoparticles, chain collapse of the PDMAEMA above its lower critical solution temperature (LCST) might change the environment of the SIP block, thereby altering its depolymerization rate. Self‐assembly of the block copolymers was performed, and the depolymerization of the resulting assemblies was studied by fluorescence spectroscopy, dynamic light scattering, and NMR spectroscopy. At 20 °C, the system exhibited a selective response to the UV light. At 65 °C, above the LCST of PDMAEMA, the systems underwent more rapid depolymerization, suggesting that the increase in rate arising from the higher temperature dominated over environmental effects arising from chain collapse. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1868–1877     

pH‐Triggered Self‐Assembly of Cellulose Oligomers with Gelatin into a Double‐Network Hydrogel

Multicomponent systems for self‐assembled molecular gels provide huge opportunities to generate collective or new functions that are not inherent in individual single‐component gels. However, gelation tends to require careful and complicated procedures, because, among a myriad of kinetically trapped structures related to the degree of mixing of multiple components over a wide range of scales, from molecular level to macroscopic scale, a limited number of structures that exhibit the desired function need to be constructed. This study presents a simple method for the construction of double‐network (DN) hydrogels with improved stiffness composed of crystalline cellulose oligomers and gelatin. The pH‐triggered self‐assembly of cellulose oligomers leads to the formation of robust networks composed of crystalline nanofibers in the presence of dissolved gelatin, followed by cooling to allow for the formation of soft gelatin networks. The resultant DN hydrogels exhibit improved stiffness; the improvement in gel stiffness with double networking is comparable to that of previously reported DN hydrogels produced via a time‐consuming enzymatic reaction.     

Folding‐Induced Modulation of Excited‐State Dynamics in an Oligophenylene–Ethynylene‐Tethered Spiral Perylene Bisimide Aggregate

The excited‐state photophysical behavior of a spiral perylene bisimide (PBI) folda‐octamer ( F8 ) tethered to an oligophenylene–ethynylene scaffold is comprehensively investigated. Solvent‐dependent UV/Vis and fluorescence studies reveal that the degree of folding in this foldamer is extremely sensitive to the solvent, thus giving rise to an extended conformation in CHCl₃ and a folded helical aggregate in methylcyclohexane (MCH). The exciton‐deactivation dynamics are largely governed by the supramolecular structure of F8 . Femtosecond transient absorption (TA) in the near‐infrared region indicates a photoinduced electron‐transfer process from the backbone to the PBI core in the extended conformation, whereas excitation power‐ and polarization‐dependent TA measurements combined with computational modeling showed that excitation energy transfer between the unit PBI chromophores is the major deactivation pathway in the folded counterpart.     

Unexpected Self‐Sorting Self‐Assembly Formation of a [4:4] Sulfate:Ligand Cage from a Preorganized Tripodal Urea Ligand

The design and synthesis of tripodal ligands 1 – 3 based upon the N‐methyl‐1,3,5‐benzenetricarboxamide platform appended with three aryl urea arms is reported. This ligand platform gives rise to highly preorganized structures and is ideally suited for binding SO₄^2? and H₂PO₄^? ions through multiple hydrogen‐bonding interactions. The solid‐state crystal structures of 1 – 3 with SO₄^2? show the encapsulation of a single anion within a cage structure, whereas the crystal structure of 1 with H₂PO₄^? showed that two anions are encapsulated. We further demonstrate that ligand 4 , based on the same platform but consisting of two bis‐urea moieties and a single ammonium moiety, also recognizes SO₄^2? to form a self‐assembled capsule with [4:4] SO₄^2?: 4 stoichiometry in which the anions are clustered within a cavity formed by the four ligands. This is the first example of a self‐sorting self‐assembled capsule where four tetrahedrally arranged SO₄^2? ions are embedded within a hydrophobic cavity.     

Solution‐Processable Flower‐Shaped Hierarchical Structures: Self‐Assembly,Formation, and State Transition of Biomimetic Superhydrophobic Surfaces

Superhydrophobic surfaces inspired by biological microstructures attract considerable attention from researchers because of their potential applications. In this contribution, two kinds of microscale flower‐shaped morphologies with nanometer petals formed from the hierarchical self‐assembly of benzothiophene derivatives bearing long alkyl chains have been developed as superhydrophobic surfaces. The intermediate stages of the assemblies demonstrated a new formation mechanism for such flower‐shaped morphologies. The hierarchical morphologies of the film exhibited excellent water‐repelling characteristics as superhydrophobic surfaces, which were prepared by means of a simple solution process. The transition process from the Cassie state to Wenzel state was easily realized owing to the slight microstructural differences in the two kinds of flowers caused by their different chemical structures. The superhydrophobicity of such functional materials might be beneficial for applications in electrical devices in which the presence of water would influence their performance.     

Synthesis of a Benzenethiol‐derivatized Porphyrin for Self‐assembly

The synthesis of a benzenethiol‐derivatized porphyrin for flat‐lying self‐assembly on gold substrates is described. Acetyl protected thiol is not stable enough in Pd‐catalyzed reactions. While acrylate derivatives protected thiol group shows good tolerance in Pd‐catalyzed borylations and Suzuki‐Miyaura coupling reactions and no catalyst poisoning was observed.     

β‐cyclodextrin‐based polymeric nano‐receptor: the self‐assembly of cyclodextrin‐appended comb‐copolymer

Well‐defined β‐cyclodextrin (β‐CD)‐appended biocompatible comb‐copolymer ethyl cellulose‐graft‐poly (ε‐caprolactone) (EC‐g‐PCL) was synthesized via the combination of ring‐opening polymerization (ROP) and click chemistry. The resulting products were characterized by ¹H NMR, FT‐IR spectroscopy, and GPC. The synthesized comb‐copolymer could assemble to micelles, with the surface covered by β‐CD. The inclusion with ferrocene derivation was investigated by cyclic voltammetric (CV) experiments, which indicated the potential application of the micelles as nano‐receptors for molecule recognization and controlled drug release. Copyright © 2011 John Wiley & Sons, Ltd.     

Fluorescence Detection of Microcapsule‐Type Self‐Healing,Based on Aggregation‐Induced Emission

An extrinsic self‐healing coating system containing tetraphenylethylene (TPE) in microcapsules was monitored by measuring aggregation‐induced emission (AIE). The core healing agent comprised of methacryloxypropyl‐terminated polydimethylsiloxane, styrene, benzoin isobutyl ether, and TPE was encapsulated in a urea‐formaldehyde shell. The photoluminescence of the healing agent in the microcapsules was measured that the blue emission intensity dramatically increased and the storage modulus also increased up to 10⁵ Pa after the photocuring. These results suggested that this formulation might be useful as a self‐healing material and as an indicator of the self‐healing process due to the dramatic change in fluorescence during photocuring. To examine the ability of the healing agent to repair damage to a coating, a self‐healing coating containing embedded microcapsules was scribed with a razor. As the healing process proceeded, blue light fluorescence emission was observed at the scribed regions. This observation suggested that self‐healing could be monitored using the AIE fluorescence.

     

Metal‐Folded Single‐Chain Nanoparticle: Nanoclusters and Self‐Assembled Reduction‐Responsive Sub‐5‐nm Discrete Subdomains

Easy access to discrete nanoclusters in metal‐folded single‐chain nanoparticles (metal‐SCNPs) and independent ultrafine sudomains in the assemblies via coordination‐driven self‐assembly of hydrophilic copolymer containing 9% imidazole groups is reported herein. ¹H NMR, dynamic light scattering, and NMR diffusion‐ordered spectroscopy results demonstrate self‐assembly into metal‐SCNPs (>70% imidazole‐units folded) by neutralization in the presence of Cu(II) in water to pH 4.6. Further neutralization induces self‐assembly of metal‐SCNPs (pH 4.6–5.0) and shrinkage (pH 5.0–5.6), with concurrent restraining residual imidazole motifs and hydrophilic segment, which organized into constant nanoparticles over pH 5.6–7.5. Atomic force microscopy results evidence discrete 1.2 nm nanoclusters and sub‐5‐nm subdomains in metal‐SCNP and assembled nanoparticle. Reduction of metal center using sodium ascorbate induces structural rearrangement to one order lower than the precursor. Enzyme mimic catalysis required media‐tunable discrete ultrafine interiors in metal‐SCNPs and assemblies have hence been achieved.     

Synthesis and self‐assembly behavior study of α,ω‐dicarboxyl‐poly(ethylene glycol)–permethyl‐6‐amino‐6‐deoxy‐β‐cyclodextrin‐monoamide: A new β‐cyclodextrin conjugate

A new type of amphiphilic macromolecule was synthesized through the attachment of a poly(ethylene glycol) chain to a permethyl‐amino‐β‐cyclodextrin ring. The structure of the product was studied with 1D and 2D NMR experiments and with MALDI‐TOF MS. The resulting comet‐shaped molecule showed self‐assembly behavior in polar solvents. The presence of supramolecular structures in aqueous media was detected with dynamic light scattering and proven also by 2D NOESY and DOSY experiments. The supramolecular structures that formed could serve as starting materials for new types of drug delivery bioconjugates containing two independent dopable sites, that is, the cyclodextrin ring and the core of the supramolecular structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5149–5155, 2007