Design Rules for Binary Bisamide Gelators: toward Gels with Tailor-Made Structures and Properties

This study intends to develop design rules for binary mixture of gelators that govern their assembly behavior and subsequently explore the impact of their supramolecular assembly patterns on the gels' rheological properties. To achieve these goals, nBA gelators with odd and even parities [n-methylene spacers between the amide groups (n = 5-10) and 17 carbons at each end] were blended at different ratios. Such bisamides with simple structures were selected to study because their different spacer lengths offer the possibility to have matching or non-matching hydrogen bonds. The results show that the assembly behavior of binary mixtures of bisamide gelators is the same in the solid and gel states. Binary mixtures of gelators, which only differ two methylene moieties in the spacer length, form compounds and co-assemble into fibers and sheets observed for (5BA)1(7BA)1 and (6BA)1(8BA)1 mixtures, respectively. Binary gelator mixtures of the same parity and a larger spacer length difference still lead to mixing for the odd parity couple (5BA)1(9BA)1), but to partial phase separation for the even parity mixture (6BA)1(10BA)1. Binary mixtures of gelators of different parities gave complete phase separation in the solid state, and self-sorted gels consisting of discrete fibers and sheets in the gels of (5BA)3(6BA)1 and (5BA)3(10BA)1. The even-even binary gels (20 wt %) consisting of co-assembled sheets show higher G' than odd-odd binary gels (20 wt %) consisting of co-assembled fibers. In general, the self-sorting of odd and even molecules into the separate primary structures results in a dramatic decrease of G' compared to the co-assembled gels (20 wt %), except for (5BA)1(9BA)1 gel (20 wt %). It might be due to larger woven spheres in (5BA)1(9BA)1 gel (20 wt %), which probably have a less entangled gel network.

The Role of Functional Groups in Tuning the Self-Assembly Modes and Physical Properties of Multicomponent Gels

We have analyzed the nature and role of functional groups on the self-assembly modes and the physical properties of multicomponent gels with structurally similar individual components. The gelation properties of individual and mixed enantiomeric compounds of biphenyl bis-(amides) of alanine (BPA) or phenylalanine (BPP) methyl ester were analyzed in various solvent/solvent mixtures. Multicomponent gels were formed by mixing the enantiomeric BPP compounds at a lower concentration, but a higher concentration was required for mixed alanine-based BPA gels. The comparison of the mechanical strength of the individual and mixed BPP compounds indicated that the mixed BPP gels displayed enhanced mechanical strength (∼2-fold increase) in p-xylene, but a weaker gel was observed in DMSO/water. However, a reverse trend was observed for BPA gels, indicating the role of functional groups in the gel network formation. X-ray diffraction analysis of the gelator and the xerogels in the solid state confirmed the formation of co-assembled networks in mixed enantiomeric gels. The stability of the gels towards anions was evaluated by analyzing the anion induced stimuli-responsive properties. These results indicate the effective modeling of the functional groups of the individual components could lead to multicomponent gels with tunable properties.

Self-Sorting in Diastereomeric Mixtures of Functionalized Dipeptides

Self-sorting in functionalized dipeptide systems can be driven by the chirality of a single amino acid, both at a high pH in the micellar state and at a low pH in the gel state. The structures formed are affected to some degree by the relative concentrations of each component showing the complexity of such an approach. The structures underpinning the gel network are predefined by the micellar structures at a high pH. Here, we describe the systems prepared from two dipeptide-based gelators that differ only by the chirality of one of the amino acids. We provide firm evidence for self-sorting in the micellar and gel phases using small-angle neutron scattering and cryo-transmission electron microscopy (cryo-TEM), showing that complete self-sorting occurs across a range of relative concentrations.

Stabilization of DNA Duplexes and Hairpins by Charge-Transfer Interactions Using DAN:NDI Pairs

Electron-rich 1,5-dialkoxynaphthalene (DAN) and electron-deficient 1,8,4,5-naphthalenetetracarboxylic diimide (NDI) are known to interact through the formation of charge-transfer complexes. The introduction of DAN and NDI into various DNA duplexes and hairpins was investigated by ultraviolet (UV) melting curve analysis. The positioning of the DAN:NDI pair was found to strongly influence the stability of DNA duplex and hairpins. In particular, while the introduction of one DAN/NDI pair in front of each other in the center of a DNA duplex led to a decrease of the thermal stability (ΔTm - 6 °C), the addition of a second pair restored or even increased the stability. In contrast, the introduction of DAN:NDI pairs at the end of a duplex always induced a strong stabilization (ΔTm up to +20 °C). Finally, a DAN:NDI pair positioned in the loop of a hairpin induced a stronger stabilization than a T4 loop (ΔTm + 10 °C). Based on charge-transfer interactions, the strong stabilizations observed allow the preparation of highly stabilized DNA nanostructures opening the way to numerous applications in nanotechnology.

Pathway Complexity in Supramolecular Copolymerization and Blocky Star Copolymers by a Hetero-Seeding Effect

This study unravels the intricate kinetic and thermodynamic pathways involved in the supramolecular copolymerization of the two chiral dipolar naphthalene monoimide (NMI) building blocks (O-NMI and S-NMI), differing merely by a single heteroatom (oxygen vs sulfur). O-NMI exhibits distinct supramolecular polymerization features as compared to S-NMI in terms of its pathway complexity, hierarchical organization, and chiroptical properties. Two distinct self-assembly pathways in O-NMI occur due to the interplay between the competing dipolar interactions among the NMI chromophores and amide-amide hydrogen (H)-bonding that engenders distinct nanotapes and helical fibers, from its antiparallel and parallel stacking modes, respectively. In contrast, the propensity of S-NMI to form only a stable spherical assembly is ascribed to its much stronger amide-amide H-bonding, which outperforms other competing interactions. Under the thermodynamic route, an equimolar mixture of the two monomers generates a temporally controlled chiral statistical supramolecular copolymer that autocatalytically evolves from an initially formed metastable spherical heterostructure. In contrast, the sequence-controlled addition of the two monomers leads to the kinetically driven hetero-seeded block copolymerization. The ability to trap O-NMI in a metastable state allows its secondary nucleation from the surface of the thermodynamically stable S-NMI spherical "seed", which leads to the core-multiarmed "star" copolymer with reversibly and temporally controllable length of the growing O-NMI "arms" from the S-NMI "core". Unlike the one-dimensional self-assembly of O-NMI and its random co-assembly with S-NMI, which are both chiral, unprecedentedly, the preferred helical bias of the nucleating O-NMI fibers is completely inhibited by the absence of stereoregularity of the S-NMI "seed" in the "star" topology.

Supramolecular Recognition of Phosphodiester-Based Donor and Acceptor Oligomers Forming Gels in Water

Inspired by automated DNA synthesis, electron-rich dialkoxynaphthalene (DAN) donor and electron-deficient naphthalene-tetracarboxylic diimide (NDI) acceptor phosphodiester-linked homohexamers were synthesized by the phosphoramidite method. Two types of hexamers were prepared, one with only one phosphodiester between the aromatics (i.e., DAN or NDI) and a second with two phosphodiesters around a propanediol between the aromatics, leading to the latter more flexible and more hydrophilic hexamers. The folding properties of these homohexamers alone or mixed together, in water only, were studied by UV-visible absorption spectroscopy and atomic force microscopy (AFM). AFM imaging revealed that a 1:1 mixture of hexaDAN and hexaNDI formed fibers by charge transfer donor-acceptor recognition leading to a hydrogel after drying. The organization of the resulting structures is strongly dependent on the nature of the complementary partner, leading to the formation of mono- or multilayer hydrogel networks with different compactness.

Crystallization-Driven Controlled Two-Dimensional (2D) Assemblies from Chromophore-Appended Poly(L-lactide)s: Highly Efficient Energy Transfer on a 2D Surface

A rational approach towards precision two-dimensional (2D) assemblies by crystallization-driven self-assembly (CDSA) of poly(L-lactides) (PLLAs), end-capped with dipolar dyes like merocyanine (MC) or naphthalene monoimide (NMI) and hydrophobic pyrene (PY) or benzene (Bn) is described. PLLA chains crystallize into diamond-shaped platelets in isopropanol, which forces the terminal dyes to assemble into a 2D array on the platelet surface by either dipolar interactions or π-stacking and exhibit tunable emission. Dipolar dyes play a critical role in imparting colloidal stability and structural uniformity to the 2D crystals, which is partly compromised for hydrophobic ones. Co-crystallization between NMI- and PY-labeled PLLAs yields similar diamond-shaped co-platelets with highly efficient (≈80 %) Förster Resonance Energy Transfer on the 2D surface. Further, the "living" CDSA method confers enlarged, segmented block co-platelets using one of the homopolymers as "seed" and the other as "unimer".

Manipulating the Self-Assembly of Multicomponent Low Molecular Weight Gelators (LMWGs) through Molecular Design

Multicomponent low molecular weight gelators (LMWGs) may self-assemble by co-assembly (CA), social self-sorting (SSS), or narcissistic self-sorting (NSS). Understanding the nuances of the self-assembly processes is important to predict the behavior of multicomponent organogels. Here, we investigate the effect of molecular structure on self-assembly in a series of amino-acid based bicomponent LMWGs that differ in headgroup and alkyl chain length. Packing preference of the organogels was determined using differential scanning calorimetry, nuclear magnetic resonance spectroscopy and small angle X-ray scattering. From 66 bicomponent samples we found 50 CA, 14 SSS and 2 NSS. Furthermore, we performed statistical analysis to investigate the role of hydrophobicity and chain length on the overall pathway of self-assembly for these systems. We found the hydrophobicity of the headgroup strongly affected the assembly preference of the organogel, but alkyl chain length only played a small role.

Tuning the donor-acceptor interactions in phase-segregated block molecules

The assembly of donor-acceptor molecules via charge transfer (CT) interactions gives rise to highly ordered nanomaterials with appealing electronic properties. Here, we present the synthesis and bulk co-assembly of pyrene (Pyr) and naphthalenediimide (NDI) functionalized oligodimethylsiloxanes (oDMS) of discrete length. We tune the donor-acceptor interactions by connecting the pyrene and NDI to the same oligomer, forming a heterotelechelic block molecule (NDI-oDMSPyr), and to two separate oligomers, giving Pyr and NDI homotelechelic block molecules (Pyr-oDMS and NDI-oDMS). Liquid crystalline materials are obtained for binary mixtures of Pyr-oDMS and NDI-oDMS, while crystallization of the CT dimers occurred for the heterotelechelic NDI-oDMS-Pyr block molecule. The synergy between crystallization and phase-segregation coupled with the discrete length of the oDMS units allows for perfect order and sharp interfaces between the insulating siloxane and CT layers composed of crystalline CT dimers. We were able to tune the lamellar domain spacing and donor-acceptor CT interactions by applying pressures up to 6 GPa on the material, making the system promising for soft-material nanotechnologies. These results demonstrate the importance of the molecular design to tune the CT interactions and stability of a CT material.

Colored Janus Nanocylinders Driven by Supramolecular Coassembly of Donor and Acceptor Building Blocks

Janus nanocylinders exhibit nanometric dimensions, a high aspect ratio, and two faces with different chemistries (Janus character), making them potentially relevant for applications in optics, magnetism, catalysis, surface nanopatterning, or interface stabilization, but they are also very difficult to prepare by conventional strategies. In the present work, Janus nanocylinders were prepared by supramolecular coassembly in water of two different polymers functionalized with complementary assembling units. The originality of our approach consists in combining charge transfer complexation between electron-rich and electron-poor units with hydrogen bonding to (1) drive the supramolecular formation of one-dimensional structures (cylinders), (2) force the two polymer arms on opposite sides of the cylinders independently of their compatibility, resulting in Janus nanoparticles, and (3) detect coassembly through a color change of the solution upon mixing of the functional polymers.

Self-assembly of amphiphilic aryl-squaramides in water driven by dipolar π–π interactions

Amphiphilic aryl-squaramides self-assemble via unprecedented dipolar π–π interactions forming well-defined supramolecular aggregates and self-consistent hydrogels in water

Sequential Assembly of Mutually Interactive Supramolecular Hydrogels and Fabrication of Multi-Domain Materials

A two-component self-sorting hydrogel based on acylhydrazide and carboxylic acid derivatives of 1,3:2,4-dibenzylidene-d-sorbitol (DBS-CONHNH₂ and DBS-COOH) is reported. A heating-cooling cycle induces the self-assembly of DBS-CONHNH₂ , followed by the self-assembly of DBS-COOH induced by decreasing pH. Although the networks are formed sequentially, there is spectroscopic evidence of interactions between them, which impact on the mechanical properties and significantly enhance the ability of these low-molecular-weight gelators (LMWGs) to form gels when mixed. The DBS-COOH network can be switched "off" and "on" within the two-component gel through a pH change. By using a photo-acid generator, the two-component gel can be prepared combining the thermal trigger with photo-irradiation. Photo-patterned self-assembly of DBS-COOH within a pre-formed DBS-CONHNH₂ gel under a mask yields spatially controlled multi-domain gels. Different gel domains can have different functions, for example, controlling the rate of release of heparin incorporated into the gel, or directing gold nanoparticle assembly. Such photo-patterned multi-component hydrogels have potential applications in regenerative medicine or bio-nano-electronics.

Self-assemblies of nucleolipid supramolecular synthons show unique self-sorting and cooperative assembling process

The inherent control of the self-sorting and co-assembling process that has evolved in multi-component biological systems is not easy to emulate in vitro using synthetic supramolecular synthons. Here, using the basic component of nucleic acids and lipids, we describe a simple platform to build hierarchical assemblies of two component systems, which show an interesting self-sorting and co-assembling behavior. The assembling systems are made of a combination of amphiphilic purine and pyrimidine ribonucleoside-fatty acid conjugates (nucleolipids), which were prepared by coupling fatty acid acyl chains of different lengths at the 2'-O- and 3'-O-positions of the ribose sugar. Individually, the purine and pyrimidine nucleolipids adopt a distinct morphology, which either supports or does not support the gelation process. Interestingly, due to the subtle difference in the order of formation and stability of individual assemblies, different mixtures of supramolecular synthons and complementary ribonucleosides exhibit a cooperative and disruptive self-sorting and co-assembling behavior. A systematic morphological analysis combined with single crystal X-ray crystallography, powder X-ray diffraction (PXRD), NMR, CD, rheological and 3D X-ray microtomography studies provided insights into the mechanism of the self-sorting and co-assembling process. Taken together, this approach has enabled the construction of assemblies with unique higher ordered architectures and gels with remarkably enhanced mechanical strength that cannot be derived from the respective single component systems.

Charge transfer liquid: a stable donor–acceptor interaction in the solvent-free liquid state

A new charge transfer solvent-free liquid having high stability even with donor–acceptor ratio of 1000 : 1 is demonstrated.

Chiral Assembly Preferences and Directing Effects in Supramolecular Two-Component Organogels

The impact of chirality on the self-assembly of supramolecular gels is of considerable importance, as molecular-scale programming can be translated into nanostructuring and ultimately affect macroscopic performance. This paper explores the effect of chirality on the assembly of two-component gels comprised of a second-generation dendritic lysine peptide acid, containing three chiral centres, and an amine. This combination forms an acid⁻amine complex that assembles into nanofibres through peptide-peptide hydrogen bonds, leading to organogels. With achiral amines, a racemic mixture of l,l,l and d,d,d dendritic peptide acids surprisingly forms the best gels-more commonly, mixing enantiomers suppresses gelation. Thermodynamic studies demonstrate that depending on the amine, the greater stability of heterochiral gels can either be entropically or enthalpically driven. With amines possessing "R" chirality, the l,l,l peptide acid consistently forms more effective gels than its d,d,d analogue. Furthermore, in mixed gels, l,l,l sometimes imposes its assembly preference onto d,d,d. In summary, this paper demonstrates a rare example in which heterochiral gels are preferred, and also explores directing effects when each component in a two-component gel is chiral.

How should multicomponent supramolecular gels be characterised?

We discuss the current state of characterising multicomponent low molecular weight gels across all length scales, and the effectiveness of the different techniques that have been used.

Supramolecular gelatons: towards the design of molecular gels

The concept of supramolecular gelatons for the design of gels was proposed and described.

The sensitivity of donor - acceptor charge transfer to molecular geometry in DAN - NDI based supramolecular flower-like self-assemblies

A charge-transfer (CT) complex self-assembled from an electron acceptor (NDI-EA: naphthalene diimide with appended diamine) and an electron donor (DAN: phosphonic acid-appended dialkoxynapthalene) in aqueous medium. The aromatic core of the NDI and the structure of DAN1 were designed to optimize the dispersive interactions (π-π and van der Waals interactions) in the DAN1–NDI-EA self-assembly, while the amino groups of NDI also interact with the phosphonic acid of DAN1 via electrostatic forces. This arrangement prevented crystallization and favored the directional growth of 3D flower nanostructures. This molecular geometry that is necessary for charge transfer to occur was further evidenced by using a mismatching DAN2 structure. The flower-shaped assembly was visualized by scanning electron and transmission electron microscopy. The formation of the CT complex was determined by UV-vis and cyclic voltammetry and the photoinduced electron transfer to produce the radical ion pair was examined by femtosecond laser transient absorption spectroscopic measurements.

Multi-component hybrid hydrogels - understanding the extent of orthogonal assembly and its impact on controlled release

This paper reports self-assembled multi-component hybrid hydrogels including a range of nanoscale systems and characterizes the extent to which each component maintains its own unique functionality, demonstrating that multi-functionality can be achieved by simply mixing carefully-chosen constituents. Specifically, the individual components are: (i) pH-activated low-molecular-weight gelator (LMWG) 1,3;2,4-dibenzylidenesorbitol-4',4''-dicarboxylic acid (DBS-COOH), (ii) thermally-activated polymer gelator (PG) agarose, (iii) anionic biopolymer heparin, and (iv) cationic self-assembled multivalent (SAMul) micelles capable of binding heparin. The LMWG still self-assembles in the presence of PG agarose, is slightly modified on the nanoscale by heparin, but is totally disrupted by the micelles. However, if the SAMul micelles are bound to heparin, DBS-COOH self-assembly is largely unaffected. The LMWG endows hybrid materials with pH-responsive behavior, while the PG provides mechanical robustness. The rate of heparin release can be controlled through network density and composition, with the LMWG and PG behaving differently in this regard, while the presence of the heparin binder completely inhibits heparin release through complexation. This study demonstrates that a multi-component approach can yield exquisite control over self-assembled materials. We reason that controlling orthogonality in such systems will underpin further development of controlled release systems with biomedical applications.

Self-sorted Oligophenylvinylene and Perylene Bisimide Hydrogels

We describe two component hydrogels with networks composed of self-sorted fibres. The component gelators are based on 1,4-distyrylbenzene (OPV3) and perylene bisimide (PBI) units. Self-sorted gels can be formed by a slow decrease in pH, which leads to sequential assembly. We demonstrate self-sorting by NMR, rheology and small angle X-ray scattering (SAXS). Photoconductive xerogels can be prepared by drying these gels. The wavelength response of the xerogel is different to that of the PBI alone.

Supramolecular Copolymers: Structure and Composition Revealed by Theoretical Modeling

Supramolecular copolymers, non-covalent analogues of synthetic copolymers, constitute a new and promising class of polymers. In contrast to their covalent counterparts, the details of their mechanism of formation, as well as the factors determining their composition and length, are still poorly understood. Here, the supramolecular copolymerization between two slightly structurally different benzene-1,3,5-tricarboxamide (BTA) monomers functionalized with either oligodimethylsiloxane (oDMSi) or alkyl side chains is unraveled by combining experimental and theoretical approaches. By applying the "sergeant-and-soldiers" approach using circular dichroism (CD) experiments, we are able to obtain detailed insights into the structure and composition of these supramolecular copolymers. Moreover, we observe an unexpected chiral induction upon mixing two independently CD-silent solutions of the achiral (soldier) and chiral (sergeant) monomers. We find that the subtle differences in the chemical structure of the two monomers impact their homopolymerization mechanism: whereas alkyl-BTAs cooperatively self-assemble, oDMSi-BTAs self-assemble in an isodesmic manner. The effect of these mechanistic differences in the supramolecular copolymerization process is investigated as a function of the composition of the two monomers and explicitly rationalized by mathematical modeling. The results show that, at low fractions of oDMSi-BTA sergeants (<10 mol%), the polymerization process is cooperative and the supramolecular helicity is biased toward the helical preference of the sergeant. However, at higher fractions of oDMSi-BTA sergeant (>25 mol%), the isodesmic assembly of the increasing amounts of sergeant becomes more dominant, and different species start to coexist in the copolymerization process. The analysis of the experimental data with a newly developed theoretical model allows us to quantify the thermodynamic parameters, the distribution of different species, and the compositions and stack lengths of the formed supramolecular copolymers existing at various feed ratios of the two monomers.

Supramolecularly Cross-Linked Nanogel by Merocyanine Pendent Copolymer

Directional dipole-dipole interaction mediated antiparallel dimerization of merocyanine dye (MD) has been explored for maneuvering supramolecular assembly of MD-conjugated flexible macromolecules leading to a cross-linked nanogel. The MD-functionalized copolymer was synthesized by a newly developed organocatalytic transesterification strategy for postpolymerization functionalization of poly(pentafluorophenyl acrylate) (polyPFPA)-based reactive copolymer. Presence of ∼35% pendant MD attached to a coil-like polymer chain leads to spontaneous formation of highly emitting cross-linked nanogel with efficient container property and appreciable stability in toluene owing to strong dimerization propensity among the MD. Considering the significance of MD in the context of nonlinear optics and photovoltaics, these results not only enrich the toolbox for engineering macromolecular assembly, but also open up new possibilities for future organic materials.

Bimodal self-assembly of an amphiphilic gelator into a hydrogel-nanocatalyst and an organogel with different morphologies and photophysical properties

We design a flexible, amphiphilic LMWG consisting of donor and acceptor π-chromophores which self-assembles into a hydrogel and an organogel with different nano-morphologies. Different mechanisms of self-assembly evolve charge transfer (CT) emission in the hydrogel and LMWG-based emission in the organogel. Moreover, the hydrogel-nanostructure with surface exposed amide groups is explored for catalyzing Knoevenagel condensation reaction.

Supercoiled fibres of self-sorted donor-acceptor stacks: a turn-off/turn-on platform for sensing volatile aromatic compounds

To ensure the comfortable survival of living organisms, detection of different life threatening volatile organic compounds (VOCs) such as biological metabolites and carcinogenic molecules is of prime importance. Herein, we report the use of supercoiled supramolecular polymeric fibres of self-sorted donor-acceptor molecules as "turn-off/turn-on" fluorescent sensors for the detection of carcinogenic VOCs. For this purpose, a C3-symmetrical donor molecule based on oligo(p-phenylenevinylene), C3OPV, and a perylene bisimide based acceptor molecule, C3PBI, have been synthesized. When these two molecules were mixed together in toluene, in contrast to the usual charge transfer (CT) stacking, supramolecular fibres of self-sorted stacks were formed at the molecular level, primarily driven by their distinct self-assembly pathways. However, CT interaction at the macroscopic level allows these fibres to bundle together to form supercoiled ropes. An interfacial photoinduced electron transfer (PET) process from the donor to the acceptor fibres leads to an initial fluorescence quenching, which could be modulated by exposure to strong donor or acceptor type VOCs to regenerate the respective fluorescence of the individual molecular stacks. Thus, strong donors could regenerate the green fluorescence of C3OPV stacks and strong acceptors could reactivate the red fluorescence of C3PBI stacks. These supercoiled supramolecular ropes of self-sorted donor-acceptor stacks provide a simple tool for the detection of donor- or acceptor-type VOCs of biological relevance, using a "turn-off/turn-on" fluorescence mechanism as demonstrated with o-toluidine, which has been reported as a lung cancer marker.

Self-sorting regioisomers through the hierarchical organization of hydrogen-bonded rosettes

The self-assembly of two regioisomeric hydrogen-bonding naphthalenes was studied in mixed states in different polarity solvents. The regioisomers co-assemble to form heteromeric rosettes in chloroform. Upon injecting this solution into methylcyclohexane the heteromeric rosettes kinetically form amorphous aggregates, which over time differentiate into thermodynamically stable distinct nanostructures through self-sorting.

Charge-Transfer Supra-Amphiphiles Built by Water-Soluble Tetrathiafulvalenes and Viologen-Containing Amphiphiles: Supramolecular Nanoassemblies with Modifiable Dimensions

In this study, multidimensional nanoassemblies with various morphologies such as nanosheets, nanorods, and nanofibers are developed via charge-transfer interaction and supra-amphiphile self-assembling in aqueous phase. The charge-transfer interactions between tetrathiafulvalene derivatives (TTFs) and methyl viologen derivatives (MVs) have been confirmed by the characteristic charger-transfer absorption. (1) H NMR and electrospray ionizsation mass spectrometry (ESI-MS) analyses also indicate supra-amphiphiles are formed by the combination of TTFs and MVs head group through charge-transfer interaction and Coulombic force. X-ray single crystal structural studies, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) reveal that both linkage pattern of TTFs in hydrophilic part and alkane chain structure in hydrophobic part have significant influence on nanoassemblies morphology and microstructure. Moreover, gold nanoparticles (AuNPs) are introduced in the above supramolecular nanoassemblies to construct a supra-amphiphile-driven organic-AuNPs assembly system. AuNPs could be assembled into 1D-3D structures by adding different amount of MVs.

Multicomponent low molecular weight gelators

We discuss the potential and challenges of multicomponent low molecular weight gels.

The effect of self-sorting and co-assembly on the mechanical properties of low molecular weight hydrogels

Self-sorting in low molecular weight hydrogels can be achieved using a pH triggered approach. We show here that this method can be used to prepare gels with different types of mechanical properties. Cooperative, disruptive or orthogonal assembled systems can be produced. Gels with interesting behaviour can be also prepared, for example self-sorted gels where delayed switch-on of gelation occurs. By careful choice of gelator, co-assembled structures can also be generated, which leads to synergistic strengthening of the mechanical properties.

Molecular assembly of amino acid interlinked, topologically symmetric, π-complementary donor-acceptor-donor triads

Amino acid interlinked pyrene and naphthalenediimide (NDI) based novel donor–acceptor–donor (D-A-D) triads are designed to exploit their topological symmetry and complementary π-character for facile charge-transfer complexation. Consequently, free-floating high-aspect-ratio supercoiled nanofibres and hierarchical helical bundles of triads are realized by modulating the chemical functionality of interlinking amino acids.

Narcissistic versus social self-sorting of oligophenyleneethynylene derivatives: from isodesmic self-assembly to cooperative co-assembly

Narcissistic versus social! The self-assembly of two structurally related oligophenyleneethynylene derivatives featuring polar or nonpolar peripheral chains is reported. Their remarkable narcissistic versus social self-sorting behaviour in aqueous media can be controlled by concentration and solvent changes.

Hydrogen-bonding induced alternate stacking of donor (D) and acceptor (A) chromophores and their supramolecular switching to segregated states

This paper reports comprehensive studies on the mixed assembly of bis-(trialkoxybenzamide)-functionalized dialkoxynaphthalene (DAN) donors and naphthalene-diimide (NDI) acceptors due the cooperative effects of hydrogen bonding, charge-transfer (CT) interactions, and solvophobic effects. A series of DAN as well as NDI building blocks have been examined (wherein the relative distance between the two amide groups in a particular chromophore is the variable structural parameter) to understand the structure-dependent variation in mode of supramolecular assembly and morphology (organogel, reverse vesicle, etc.) of the self-assembled material. Interestingly, it was observed that when the amide functionalities are introduced to enhance the self-assembly propensity, the mode of co-assembly among the DAN and NDI chromophores no longer remained trivial and was dictated by a relatively stronger hydrogen-bonding interaction instead of a weak CT interaction. Consequently, in a highly non-polar solvent like methylcyclohexane (MCH), although kinetically controlled CT-gelation was initially noticed, within a few hours the system sacrificed the CT-interaction and switched over to the more stable self-sorted gel to maximize the gain in enthalpy from the hydrogen-bonding interaction. In contrast, in a relatively less non-polar solvent such as tetrachloroethylene (TCE), in which the strength of hydrogen bonding is inherently weak, the contribution of the CT interaction also had to be accounted for along with hydrogen bonding leading to a stable CT-state in the gel or solution phase. The stability and morphology of the CT complex and rate of supramolecular switching (from CT to segregated state) were found to be greatly influenced by subtle structural variation of the building blocks, solvent polarity, and the DAN/NDI ratio. For example, in a given D-A pair, by introducing just one methylene unit in the spacer segment of either of the building blocks a complete change in the mode of co-assembly (CT state or segregated state) and the morphology (1D fiber to 2D reverse vesicle) was observed. The role of solvent polarity, structural variation, and D/A ratio on the nature of co-assembly, morphology, and the unprecedented supramolecular-switching phenomenon have been studied by detail spectroscopic and microscopic experiments in a gel as well as in the solution state and are well supported by DFT calculations.