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Azobenzene-based materials have found applications in a wide variety of systems as a convenient method to induce photo-responsive behaviour through facile trans (E) to cis (Z) isomerization. Of particular interest are condensed matter systems, for which diverse assemblies have been applied in myriad ways to produce optical materials, controllable assemblies and functional surfaces. However, isomerization of azobenzene faces unique challenges in condensed systems when compared with dilute states (molecular solution and gas phase) where isomerization is best understood. In the present work, we explore recent studies looking at these challenges experienced in condensed matter phases, some solutions proposed to improve isomerization efficiency, and further give these issues wider context for the future development of light-responsive soft-matter systems.

Here we expand our recently reported Bristol–Xi'an Jiaotong (BXJ) approach using simple salts to fine-tune the porosity of conjugated microporous materials synthesized by various reaction approaches, including Buchwald–Hartwig (BH), Sonogashira–Hagihara, oxidative coupling and Suzuki cross-coupling. The surface area and the porosity of the produced conjugated microporous polyanilines (CMPAs) acquired from the non-salt-added BH coupling are optimized by the addition of inorganic salts. BXJ-salt addition provides a facile route to radically improve the BET surface area from 28 to 901 m2 g−1 for PTAPA and from 723 m2 g−1 to 1378 m2 g−1 for PAPA in a controllable manner. In addition, the surface area shows a gradual decrease with an increase in the ionic radius of salts. We furthermore show high compatibility of this approach in the synthesis of typical CMPs, further increasing the surface area from 886 to 1148 m2 g−1, 981 to 1263 m2 g−1, and 35 to 215 m2 g−1 for CMP-1, PTCT and p-PPF, respectively. More importantly, the BXJ approach also allows the broad PSD of the CMPs to be narrowed to the microporous range only, mimicking COFs and MOFs. With the porosity optimized, CO2 uptakes are dramatically improved by >300% from 0.75 mmol g−1 to 2.59 mmol g−1 for PTAPA and from 2.41 mmol g−1 to 2.93 mmol g−1 for PAPA. Careful addressing of Hansen solubility parameters (HSPs) of solvents and resulting polymers through salt addition has the potential to become an important design tool for the preparation of fully tuneable porous materials. We are currently exploring further methods to tune both structure and function in a wide range of organic porous materials.

Polymeric supra-amphiphiles are amphiphiles that are fabricated by linking polymeric segments, or small molecules and polymeric segments, by noncovalent interactions or dynamic covalent bonds. Compared with conventional amphiphilic polymers, polymeric supra-amphiphiles are advantageous in that they possess dynamic features and their preparation may be to some extent more facile. Moreover, polymeric supra-amphiphiles are endowed with richer structure and higher stability compared with small-molecule supra-amphiphiles. Owing to these properties, polymeric supra-amphiphiles have so far shown great promise as surfactants, nanocarriers and in therapies. In this tutorial review, recent work on polymeric supra-amphiphiles, from molecular architectures to functional assemblies, is presented and summarized. Different polymeric supra-amphiphile topologies and related applications are highlighted. By combining polymer chemistry with supramolecular chemistry and colloid science, we anticipate that the study of polymeric supra-amphiphiles will promote the continued development of the molecular engineering of functional supramolecular systems, and lead to practical applications, especially in drug delivery.

An addressable packing parameter approach was developed for reversibly tuning the self-assembly of oligo(aniline)-based supra-amphiphiles., We present a newly developed approach to non-covalently address the packing parameter of an electroactive amphiphile. The pH-responsive reversible switching of a tetra(aniline)-based cationic amphiphile, TANI-pentyl trimethylammonium bromide (TANI-PTAB), between self-assembled vesicles and nanowires by acid/base chemistry in aqueous solution is used to exemplify this approach. Trifluoroacetic acid (TFA) was selected as a prototypical acid to form emeraldine salt (ES) state (TANI(TFA)2-PTAB) vesicles for this new class of small-molecule supramolecular amphiphiles. UV-vis-NIR spectroscopy, transmission electron microscopy (TEM), tapping-mode atomic force microscopy (AFM), and fluorescence spectroscopy were used to investigate the reversible structural transformation from vesicles to nanowires. We show that utilising different protonic acid-dopants for TANI-PTAB can regulate the packing parameter, and thus the final self-assembled structures, in a predictable fashion. We envisage potential application of this concept as smart and switchable delivery systems.

The influence of processing conditions on the thin film microstructure is a fundamental question that must be understood to improve the performance of solution-processed organic electronic materials. Using grazing-incidence X-ray diffraction, we have studied the structure of thin films of a tetra(aniline)-surfactant complex prepared by drop-casting from five solvents (hexane, chloroform, tetrahydrofuran, dichloromethane and ethanol), selected to cover a range of polarities. We found that the structure, level of order and degree of orientation relative to the substrate were extremely sensitive to the solvent used. We have attempted to correlate such solvent sensitivity with a variety of solvent physical parameters. Of particular significance is the observation of a sharp structural transition in the thin films cast from more polar solvents; such films presented significantly greater crystallinity as measured by the coherence length and paracrystalline disorder parameter. We attribute this higher structural order to enhanced dissociation of the acid surfactant in the more polar solvents, which in turn promotes complex formation. Furthermore, the more polar solvents provide more effective screening of (i) the attractive ionic interaction between oppositely charged molecules, providing greater opportunity for dynamic reorganisation of the supramolecular aggregates into more perfect structures; and (ii) the repulsive interaction between the positively charged blocks permitting a solvophobic-driven aggregation of the aromatic surfaces during solvent evaporation.

An environmentally friendly method is developed to explore the self-assembly of Ph/NH2-capped tetra(aniline), TANI, nanowires in acidic aqueous media with ultrasonic irradiation. Ultrasonic irradiation is demonstrated to be an effective method to achieve self-assembled thermodynamic equilibrium for nanostructure formation in only 2 minutes. Further assembly, i.e., the formation of thicker TANI nanowires in acidic solution left undisturbed for 96 h without the addition of any organic solvent, is also investigated. The self-assembly behaviour of TANI is studied using FT-IR, Raman, UV-Vis spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Investigations suggest that extra hydrogen bonding associated with the protonation, electrostatic interactions and π–π stacking interaction are important for the self-organization of TANI nanowires. Furthermore, the assembly behaviour of TANI nanowires is dependent on the properties of the dopant, including size and concentration, and reflected in the conductivity of the assembled structures. These results provide insight to understand and tune the self-assembly behaviour of nanostructured oligo(aniline)s in complex dopant-containing systems, and form the basis for further detailed mechanistic studies.

The controlled formation of MOF-based superstructures with well-defined nanoscale sizes and exquisite morphologies represents a big challenge, but can trigger a new set of properties distinct from their bulk counterparts. Here we report on the use of a self-assembled organic object to template the first example of a nanoscale metal–organic framework (MOF) with a helical morphology. Two prototypical MOFs (HKUST-1 and MIL-100) were used to exemplify the growth of such materials on supramolecular assemblies. Interestingly, it was found that, dependent on the nature of the precursors, not only could well-defined helical MOF nanotubes be facilely fabricated, but novel helical bundle nanostructures could also be formed. These resultant MOF superstructures show additional optical properties and could be used as precursors for the preparation of chiral nanocarbons.

Conjugated microporous polytriphenylamine networks with surface areas of 530 m2 g−1 were synthesized via Buchwald–Hartwig coupling, resulting in high CO2 uptake (up to 6.5 wt%) and CO2–N2 selectivity (75) at 1 bar and 303 K.

A reversible, critical phase separation induced by UV light at 350 nm has been achieved by doping a small amount of photosensitive surfactant into an AOT-stabilised water-in-decane microemulsion. The initial and separated phases were analysed by small-angle neutron scattering (SANS), which suggests irradiation produces two coexisting water-in-oil microemulsions with relative droplet concentrations of 1 : 3. To better understand the effect of the photosurfactant, drop shape analysis tensiometry was used, showing a change in the effectiveness of the interfacial film under different irradiation conditions.

We developed a simple one-pot method to fabricate electroactive tetra(aniline)-based microcapsules, which exhibit a wide range of pH response by self-assembly. In this procedure, the microcapsules are prepared by the facile dialysis-induced self-assembly of tetra(aniline), TANI, doped with acetic acid (HAc), onto the oil-in-water droplet interface. The chemical structure of the shell is characterized by FT-IR and UV-Vis spectroscopy. The electrochemical properties, self-assembly and pH response of microcapsule dispersions are further investigated by cyclic voltammetry, optical and electron microscopy, dynamic light scattering and aqueous electrophoresis. The size of the microcapsules increases gradually from 1.25 μm to 2.93 μm when the concentration of HAc changes from 12 M to 14 M and higher (to become glacial acetic acid). Furthermore, we show that aggregation and stability of the microcapsules can be controlled through changes in pH. This strategy appears to be a general scheme for producing other oligo(aniline)-based microcapsules.

Here we report on our investigations into the aggregation behaviour and optoelectronic properties of organic (semi)conductor-containing π-conjugated rod–coil–rod triblock materials. The facile synthesis of these rod-like tetra(aniline) (TANI) containing materials was achieved by a one-step condensation reaction of mono-functional phenyl/NH2 end-capped TANI and di-functional aliphatic diacyl chloride substrates. Simple variation of the n-alkyl spacer chain length impacted on the intermolecular amide-mediated H-bonding interactions and allowed fine-tuning of dc-conductivity values over two orders of magnitude for thin films of plasticized and CSA-doped supported thin films. Initial investigations into the production of anisotropic functional structures yielded micrometer-sized spherical (vesicular or solid spheres) isotropic functional structures. This approach is identified as an area for further exploration.

Self-assembly of cationic bolaamphiphiles is usually reported to form one-dimensional (1D) or zero-dimensional (0D), rather than two-dimensional (2D) structures. Here we have found a facile counterion-directed structure switch for such amphiphilic moieties. 0D/1D structures formed by self-assembly of cationic bolaamphiphiles can be converted into 2D planar structures by a simple counterion change to tosylate. As indicated by the single crystal structure and variable-temperature NMR studies, the strong binding between tosylate counterions and cationic headgroups drives the formation of 2D planar structures. It is highly anticipated that this approach may present as a simple methodology to control the stacking of the embedded conjugated cores in bolaamphiphiles, therefore modulating optoelectronic properties and function in such assemblies.

The self-assembly behaviour, structure, and consequently the electronic properties of electroactive organic molecules can differ significantly from those of the bulk material when confined to thin films. Here we have examined the self-organised in-plane and out-of-plane structures of aniline oligomers in thin films using surface-sensitive grazing-incidence X-ray scattering (GIXS). Thin films of the aniline tetramer (TANI) and octamer (OANI) were prepared both in their native emeraldine base (EB) oxidation state and in the doped emeraldine salt (ES) state (combined with the acid surfactant bis(ethyl hexyl)phosphate (BEHP)), using a simple drop-casting and solvent annealing process. It was found that the presence of the acid surfactant induced self-organisation into highly ordered structures. The details of these structures, such as the morphology, orientation relative to the underlying substrate and the degree of orientation were found to depend on the molecular architecture of the oligomer. The BEHP-doped TANI system formed a highly oriented hexagonal unit cell (lattice parameters: a = b = 2.53 nm, c = 2.91 nm, γ = 120°), whereas the BEHP-doped OANI complex adopted a randomly oriented lamellar structure (d-spacing = 2.25 nm). Such detailed structural information reveals that the self-assembly behaviour and the packing of oligomer–BEHP complexes, when confined to thin films, are indeed different to that of the bulk phase materials. Furthermore, the molecular architecture of the oligomers directly influenced the structural changes of the doped films in response to in situ thermal treatment. These results demonstrate that through a simple processing route the morphology of electroactive oligomer films can be tailored by molecular design. These findings are important to future applications where thin film structure is a crucial consideration for device function and performance.

In this communication we present the facile preparation and characterisation of thermotropic liquid-crystalline materials from the ionic self-assembly of a charged perylenediimide derivative and oppositely charged surfactants.

A tetra(aniline)-alkyl diblock compound was designed, synthesized and fully characterized. By employing suitable conditions, doped, electroactive microstructures could be prepared. The microstructures were characterized in detail and their anisotropic conductivity measured for the first time.

Recent advances in the fast-growing area of block-like structures based on electroactive oligomers, with a particular focus on tetra(aniline)-based structures, are discussed in this review. We provide an overview of recent literature covering aspects of design of novel molecular architectures, synthetic strategies and theoretical investigations. Specifically, we discuss tetra(aniline)s (TANI), di- and tri-block architectures before providing details of recent computational studies. We highlight useful synthetic routes, advantages of utilising block-like structures, as well as opportunities for further exploration on both the synthetic and computational fronts.

The concept of ionic self-assembly (ISA) has been employed to design and prepare new redox-active thermotropic liquid-crystalline materials. These ordered anisotropic materials in the bulk state were constructed from the complexation of a series of polyferrocenylsilane (PFS) polyelectrolytes with several oppositely charged surfactants. The structural characterization of the self-assembled materials was performed using a variety of techniques including FTIR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarized optical microscopy (POM), small- and wide-angle X-ray scattering (SAXS and WAXS), transmission electron microscopy (TEM) and UV-vis spectroscopy. Results showed that strong coulombic attractions between the starting building blocks resulted in the formation of ordered mesostructures with average periodicities of 2–3 nm. The precise phase thickness of both the PFS and surfactant layers was quantitatively determined using a one-dimensional correlation function. Moreover, the redox properties of the mesomorphic organometallic PFS polyelectrolyte–surfactant complexes were systematically investigated using cyclic voltammetry (CV) and chemical redox methods. The versatility of this ISA technique also allowed the incorporation of a photoactive azobenzene-containing surfactant, resulting in ordered mesostructures with potential optoelectronic applications.

A series of complexes formed from anionic calix[4]resorcinarenes and cationic surfactants have been formulated and their structures and binding capacity for selected guests have been studied. Calix[4]resorcinarenes were sulfonated at the 2 position by a Mannich-type reaction. Combination of aqueous solutions of these systems with cationic quaternary ammonium surfactants led to soft precipitates, which, when isolated, were shown to be composites consisting of four surfactant molecules to each (tetraanionic) calix[4]resorcinarene. X-Ray scattering experiments demonstrated the presence of a regular lamellar liquid-crystal-like layer structure within cast films of these composites. Experiments on cast films of the composites showed that they proved capable of reversibly binding a range of compounds both from the vapour phase and aqueous solutions with some selectivity, indicating the potential of using these materials within a sensor.

A chiral supramolecular liquid-crystalline material was produced by the complexation of a cationic perylene bisimide dye (PTCDI) with an anionic chiral phosphate surfactant (BDP) via ionic self-assembly. The aggregation behaviour of the PTCDI–BDP complex was investigated in detail in solution and in the bulk state. The UV-Vis and CD results show that helical supramolecular aggregates of the complex were formed with the enhancement of π–π stacking between perylene molecules in solution (due to low solubility in poor solvents) as well as in the bulk. Thin films of the complex exhibit fan-shaped textures in polarized optical microscopy (POM) investigations, which corresponds to a columnar mesophase. X-ray diffraction analyses confirmed this phase identification. Moreover, the complex formed a nanofibrillar structure, as imaged by TEM, when cast from dilute ethanol solutions.

Noncovalent interactions have been used to modify the binding properties of two-armed diketopiperazine receptors by ionic self-assembly and induced the formation of liquid-crystalline (LC) materials. The properties of the LC material were in turn modified by binding to a selectively recognized peptidic guest.

Here we show that ionic self-assembly of simple biological tectons can be used to synthesize stable and highly ordered molecular structures. In particular, nucleotides and charged polypeptides can be assembled to form a complex analogous to DNA under relatively benign conditions. The combination of polylysine and pure dGMP leads to a fourfold ladder structure stabilizing an interior G-quartet structure by four polypeptide scaffolds. Making use of the Watson-Crick G∶C base pairing motive leads to double-stranded complexes. Interestingly, these complexes show stable DNA-like organization in aqueous solutions, as proven by gel electrophoresis and intercalation experiments.