The fabrication of a supra-amphiphile for dissipative self-assembly

Triply Adaptive Libraries of Dynamic Covalent Macrocycles: Switching between Sorted and Unsorted States

Dynamic noncovalent and covalent chemistries have enabled the constitutional modulation of chemical entities within chemical dynamic systems. The switching between order and disorder, i.e., self-sorted and unsorted states of constitutional dynamic libraries, remains challenging. Herein, we study the adaptive behaviors of a dynamic library of imine macrocycles generated from dialdehydes and diamines, seeking ways to exert control over sorting and unsorting processes. The distribution of constituents in the present library of dynamic macrocycles is modulated in response to internal and external effectors (e.g., time, metal cations, and chemical fuels), resulting in the transient amplification of self-sorted constituents in out-of-equilibrium states. The present study showcases higher complexity in systems subject to multiple adaptation through the dynamic interconversion between singularity/order and diversity/disorder.

Innovative Real-Time Flow Sensor Using Detergent-Free Complex Emulsions with Dual-Emissive Semi-Perfluoroalkyl Substituted Α-Cyanostilbene

In this study, the potential of complex emulsions is investigated as transducers in sensing applications. Complex emulsions are stabilized without external detergents by developing a novel α-cyanostilbene substituted with PEG and semi-perfluoroalkyl chain (CNFCPEG). CNFCPEG exhibits unique variable emission properties depending on its aggregation state, allowing dual blue and green emissions in complex emulsions with hydrocarbon-in-fluorocarbon-in-water (H/F/W) morphology. The green excimer emissions result from the self-assembly of CNFCPEG at the fluorocarbon/water interface, while the blue emission observed is due to aggregation in the organic phase. A novel flow-injection method is developed by incorporating complex emulsions with CNFCPEG into multiple-well flow chips (MWFC). Iodine is successfully detected in a mobile aqueous solution by monitoring morphology changes. The findings demonstrate that self-stabilized complex emulsions with MWFC hold great promise for real-time sensing without costly instruments.

Role of Fast and Slow Inhibitors in Oscillatory Rhythm Design

In biological or abiotic systems, rhythms occur, owing to the coupling between positive and negative feedback loops in a reaction network. Using the Semenov-Whitesides oscillatory network for thioester hydrolysis as a prototype, we experimentally and theoretically analyzed the role of fast and slow inhibitors in oscillatory reaction networks. In the presence of positive feedback, a single fast inhibitor generates a time delay, resulting in two saddle-node bifurcations and bistability in a continuously stirred tank reactor. A slow inhibitor produces a node-focus bifurcation, resulting in damped oscillations. With both fast and slow inhibitors present, the node-focus bifurcation repeatedly modulates the saddle-node bifurcations, producing stable periodic oscillations. These fast and slow inhibitions result in a pair of time delays between steeply ascending and descending dynamics, which originate from the positive and negative feedbacks, respectively. This pattern can be identified in many chemical relaxation oscillators and oscillatory models, e.g., the bromate-sulfite pH oscillatory system, the Belousov-Zhabotinsky reaction, the trypsin oscillatory system, and the Boissonade-De Kepper model. This study provides a novel understanding of chemical and biochemical rhythms and suggests an approach to designing such behavior.

Multiple iodide autocatalysis paths of chemo-hydrodynamical patterns in the Briggs-Rauscher reaction

Autocatalytic feedback is often regarded as the core step for the chemo-hydrodynamical patterns in the nonlinear reaction system. The Briggs-Rauscher (BR) reaction shows sequential chemo-hydrodynamical patterns with three states, i.e. labyrinth, high iodine state, and rotating dendritic patterns. The short-lived labyrinth patterns, depending on [Mn²⁺]₀, the ratio of [CH₂(COOH)₂]₀ and [KIO₃]₀ and light intensities, result from iodide autocatalytic loop, which has three paths (involving Mn²⁺-induced radical reactions, the oxidation of iodomalonic compounds, and light-induced radical reactions, respectively). The high iodine state appears in a high ratio of [CH₂(COOH)₂]₀ and [KIO₃]₀, relating to the autocatalytic path involving the oxidation of iodomalonic compounds. The light-induced radical autocatalytic path can act as a convenient control parameter to modulate the patterns in the first stage by increasing the iodine radicals. The dendritic patterns in the third stage result from the Marangoni effect caused by the evaporation of the solutions and reactions between H₂O₂ and iodine-containing species, which is independent of [CH₂(COOH)₂]₀ and [Mn²⁺]₀. This work contributes to a better understanding of the complex spatiotemporal patterns in the chemo-hydrodynamical system.

Construction of transient supramolecular polymers controlled by mass transfer in biphasic systems

Inspired by life assembly systems, the construction of transient assembly systems with spatiotemporal control is crucial for developing intelligent materials. A widely adopted strategy is to couple the self-assembly with chemical reaction networks. However, orchestrating the kinetics of multiple reactions and assembly/disassembly processes without crosstalk in homogeneous solutions is not an easy task. To address this challenge, we propose a generic strategy by separating components into different phases, therefore, the evolution process of the system could be easily regulated by controlling the transport of components through different phases. Interference of multiple components that are troublesome in homogeneous systems could be diminished. Meanwhile, limited experimental parameters are involved in tuning the mass transfer instead of the complex kinetic matching and harsh reaction selectivity requirements. As a proof of concept, a transient metallo-supramolecular polymer (MSP) with dynamic luminescent color was constructed in an oil-water biphasic system by controlling the diffusion of the deactivator (water molecules) from the water phase into the oil phase. The lifetime of transient MSP could be precisely regulated not only by the content of chemical fuel, but also factors that affect the efficiency of mass transfer in between phases, such as the volume of the water phase, the stirring rate, and the temperature. We believe this strategy can be further extended to multi-compartment systems with passive diffusion or active transport of components, towards life-like complex assembly systems.

Temporally programmed polymer - solvent interactions using a chemical reaction network

Out of equilibrium operation of chemical reaction networks (CRNs) enables artificial materials to autonomously respond to their environment by activation and deactivation of intermolecular interactions. Generally, their activation can be driven by various chemical conversions, yet their deactivation to non-interacting building blocks remains largely limited to hydrolysis and internal pH change. To achieve control over deactivation, we present a new, modular CRN that enables reversible formation of positive charges on a tertiary amine substrate, which are removed using nucleophilic signals that control the deactivation kinetics. The modular nature of the CRN enables incorporation in diverse polymer materials, leading to a temporally programmed transition from collapsed and hydrophobic to solvated, hydrophilic polymer chains by controlling polymer-solvent interactions. Depending on the layout of the CRN, we can create stimuli-responsive or autonomously responding materials. This concept will not only offer new opportunities in molecular cargo delivery but also pave the way for next-generation interactive materials.

Insights into Chemically Fueled Supramolecular Polymers

Supramolecular polymerization can be controlled in space and time by chemical fuels. A nonassembled monomer is activated by the fuel and subsequently self-assembles into a polymer. Deactivation of the molecule either in solution or inside the polymer leads to disassembly. Whereas biology has already mastered this approach, fully artificial examples have only appeared in the past decade. Here, we map the available literature examples into four distinct regimes depending on their activation/deactivation rates and the equivalents of deactivating fuel. We present increasingly complex mathematical models, first considering only the chemical activation/deactivation rates (i.e., transient activation) and later including the full details of the isodesmic or cooperative supramolecular processes (i.e., transient self-assembly). We finish by showing that sustained oscillations are possible in chemically fueled cooperative supramolecular polymerization and provide mechanistic insights. We hope our models encourage the quantification of activation, deactivation, assembly, and disassembly kinetics in future studies.

An autonomously oscillating supramolecular self-replicator

A key goal of chemistry is to develop synthetic systems that mimic biology, such as self-assembling, self-replicating models of minimal life forms. Oscillations are often observed in complex biological networks, but oscillating, self-replicating species are unknown, and how to control autonomous supramolecular-level oscillating systems is also not yet established. Here we show how a population of self-assembling self-replicators can autonomously oscillate, so that simple micellar species repeatedly appear and disappear in time. The interplay of molecular and supramolecular events is key to observing oscillations: the repeated formation and disappearance of compartments is connected to a reaction network where molecular-level species are formed and broken down. The dynamic behaviour of our system across different length scales offers the opportunities for mass transport, as we demonstrate via reversible dye uptake. We believe these findings will inspire new biomimetic systems and may unlock nanotechnology systems such as (supra)molecular pumps, where compartment formation is controlled in time and space.

Iodine clocks: applications and untapped opportunities in materials science

Iodine clocks are fascinating nonlinear chemical systems with a glorious past and a promising future. The dynamic removal of iodine from these systems by different means can have important consequences for their reaction dynamics, and could be exploited for time-controlled autonomous dissipative self-assembly. Here, the untapped opportunities offered by iodine clocks for materials science, especially for the time-programming of supramolecular assembly and sol–gel transition, are reviewed and discussed with the hope of arousing the interest on the subject and stimulating new research directions.

pH Oscillator-Driven Jellyfish-like Hydrogel Actuator with Dissipative Synergy between Deformation and Fluorescence Color Change

Development of soft actuators with complex practical functions is significant for imitating the behaviors of living organisms. However, it is still a challenge to fabricate artificial soft actuators with jellyfish-like synergistic deformation and fluorescence color change (SDFC) and autonomous dynamic behavior, but such a system could obviously endow the classic soft actuators with more functions. Herein, we proposed to utilize tetra(4-pyridylphenyl)ethylene (TPE-4N) luminogen with pH-responsive aggregation-induced emission (AIE) to fabricate the AIE active hydrogel, which could be further employed to obtain an anisotropic bilayer soft actuator based on strong interfacial adhesion with acrylic acid (AA) gels. Furthermore, artificial flower-shape actuators showing SDFC behaviors were demonstrated. On the basis of these findings, jellyfish-inspired autonomous gel actuators driven by a pH oscillator have been fabricated, in which periodical SDFC behaviors completely regulated by the system itself without repetitive on/off switches of external stimuli were well synchronized with the pH oscillator. The described combination of nonlinear chemistry and responsive hydrogels actuator opens pathways toward out-of-equilibrium SDFC devices with autonomous behavior useful for biomimetic fields.

Transient chirality inversion during racemization of a helical cobalt(III) complex

SignificanceWe first observed a transient chirality inversion on a simple unimolecular platform during the racemization of a chiral helical complex [LCo₃A₆]³⁺, i.e., the helicity changed from P-rich (right-handed) to M-rich (left-handed), which then racemized to a P/M equimolar mixture in spite of the absence of a reagent that could induce the M helix. This transient chirality inversion was observed only in the forward reaction, whereas the reverse reaction showed a simple monotonic change with an induction time. Consequently, the M helicity appeared only in the forward reaction. These forward and reverse reactions constitute a hysteretic cycle. Compounds showing such unique time responses would be useful for developing time-programmable switchable materials that can control the physical/chemical properties in a time-dependent manner.

Supramolecular Engineering of Alkylated, Fluorinated, and Mixed Amphiphiles

The rational design of perfluorinated amphiphiles to control the supramolecular aggregation in aqueous medium is still a key challenge for the engineering of supramolecular architectures. Here we present the synthesis and physical properties of six novel non-ionic amphiphiles. We also studied the effect of mixed alkylated and perfluorinated segments in a single amphiphile and compared it with only alkylated and perfluorinated units. To explore their morphological behavior in aqueous medium, we used dynamic light scattering (DLS) and cryo-TEM/EM measurements. We further confirmed their assembly mechanisms with theoretical investigations, using the Martini model to perform large-scale coarse-grained molecular dynamics simulations. These novel synthesized amphiphiles offer a greater and more systematic understanding of how perfluorinated systems assemble in aqueous medium and suggest new directions for rational designing of new amphiphilic systems and interpreting their assembly process. This article is protected by copyright. All rights reserved.

Modulation of spatiotemporal dynamics in the bromate–sulfite–ferrocyanide reaction system by visible light

We have carried out the first systematic study of the effects of visible light on the homogenous dynamics in the bromate–sulfite–ferrocyanide (BSF) reaction. Under flow conditions, the reaction system displayed photoinduction and photoinhibition behavior, and the oscillatory period decreased with the increase of light intensity, which is due to the fact that light irradiation mainly enhanced the negative process and affected the positive feedback. The light effect on positive and negative feedback is studied by analyzing the period length of pH increasing and decreasing in detail. With the increase of light intensity, the period length of pH increasing decreases monotonically, while the period length of pH decreasing changes nonmonotonically. These results suggest that light could be used as a powerful tool to control homogenous dynamics. Results obtained from numerical simulations are in good agreement with experimental data.

The BSF reaction system displayed photoinduction and photoinhibition behavior under flow conditions. The oscillatory period decreased as the light irradiation mainly enhanced the negative process and affected the positive feedback.

Does Stochasticity Favour Complexity in a Prebiotic Peptide-Micelle System?

A primordial environment that hosted complex pre- or proto-biochemical activity would have been subject to random fluctuations. A relevant question is then: What might be the optimum variance of such fluctuations, such that net progress could be made towards a living system? Since lipid-based membrane encapsulation was undoubtedly a key step in chemical evolution, we used a peptide-micelle system in simulated experiments where simple micelles and peptide-stabilized micelles compete for the same amphiphilic lipid substrate. As cyclic thermal driver and energy source we used a thermochemical redox oscillator, to which the micelle reactions are coupled thermally through the activation energies. The long-time series averages taken for increasing values of the fluctuation variance show two distinct minima for simple micelles, but are smoothly increasing for complex micelles. This result suggests that the fluctuation variance is an important parameter in developing and perpetuating complexity. We hypothesize that such an environment may be self-selecting for a complex, evolving chemical system to outcompete simple or parasitic molecular structures.

Light-fueled transient supramolecular assemblies in water as fluorescence modulators

Dissipative self-assembly, which requires a continuous supply of fuel to maintain the assembled states far from equilibrium, is the foundation of biological systems. Among a variety of fuels, light, the original fuel of natural dissipative self-assembly, is fundamentally important but remains a challenge to introduce into artificial dissipative self-assemblies. Here, we report an artificial dissipative self-assembly system that is constructed from light-induced amphiphiles. Such dissipative supramolecular assembly is easily performed using protonated sulfonato-merocyanine and chitosan based molecular and macromolecular components in water. Light irradiation induces the assembly of supramolecular nanoparticles, which spontaneously disassemble in the dark due to thermal back relaxation of the molecular switch. Owing to the presence of light-induced amphiphiles and the thermal dissociation mechanism, the lifetimes of these transient supramolecular nanoparticles are highly sensitive to temperature and light power and range from several minutes to hours. By incorporating various fluorophores into transient supramolecular nanoparticles, the processes of aggregation-induced emission and aggregation-caused quenching, along with periodic variations in fluorescent color over time, have been demonstrated. Transient supramolecular assemblies, which act as fluorescence modulators, can also function in human hepatocellular cancer cells.

Dissipative self-assembly, which requires a continuous supply of fuel to maintain the assembled states far from equilibrium, is the foundation of biological systems but it remains a challenge to introduce light as fuel into artificial dissipative self-assemblies. Here, the authors report an artificial dissipative self-assembly system that is constructed from light-induced amphiphiles.

Concurrent self-regulated autonomous synthesis and functionalization of pH-responsive giant vesicles by a chemical pH oscillator

The semibatch BrO3--SO32- pH oscillator serves as the radical source for the in situ polymerization of the pH-responsive 2-(diisopropylamino)-ethyl methacrylate monomer on poly(ethylene-glycol)-macroCTA chain and generates an amphiphilic block copolymer. These building blocks concurrently self-assemble to micelles and then transforms to vesicles as the chain length of the hydrophobic block growths. Large amplitude oscillations in the concentration of H+ by the semibatch BrO3--SO32- are provoked when the conditions in the system are favorable. The oscillations control the protonation state of the tertiary amine group in the core segment of the block copolymer. Rhythmic assembly-disassembly of the polymer structures is observed. All processes, from the time- regulated autonomous formation of the building blocks, their self-assembly and the rhythmic disassembly-reassembly are governed by the same simple chemical system, in the same reaction vessel, without complicated multi step procedures and are fueled and kept out of equilibrium by the uniform inflow of SO32-.

Mechanism of periodic field driven self-assembly process

Dissipative self-assembly, a ubiquitous type of self-assembly in biological systems, has attracted a lot of attention in recent years. Inspired by nature, dissipative self-assembly driven by periodic external fields is often adopted to obtain controlled out-of-equilibrium steady structures and materials in experiments. Although the phenomena in dissipative self-assembly have been discovered in the past few decades, fundamental methods to describe dynamical self-assembly processes and responsiveness are still lacking. Here, we develop a theoretical framework based on the equations of motion and Floquet theory to reveal the dynamic behavior changing with frequency in the periodic external field driven self-assembly. Using the dissipative particle dynamics simulation method, we then construct a block copolymer model that can self-assemble in dilute solution to confirm the conclusions from the theory. Our theoretical framework facilitates the understanding of dynamic behavior in a periodically driven process and provides the theoretical guidance for designing the dissipative conditions.

A simple hydrogel device with flow-through channels to maintain dissipative non-equilibrium phenomena

The development of autonomous chemical systems that could imitate the properties of living matter, is a challenging problem at the meeting point of materials science and nonequilibrium chemistry. Here we design a multi-channel gel reactor in which out-of-equilibrium conditions are maintained by antagonistic chemical gradients. Our device is a rectangular hydrogel with two or more channels for the flows of separated reactants, which diffuse into the gel to react. The relative position of the channels acts as geometric control parameters, while the concentrations of the chemicals in the channels and the variable composition of the hydrogel, which affects the diffusivity of the chemicals, can be used as chemical control parameters. This flexibility allows finding easily the optimal conditions for the development of nonequilibrium phenomena. We demonstrate this straightforward operation by generating diverse spatiotemporal patterns in different chemical reactions. The use of additional channels can create interacting reaction zones.

Organocatalytic Control over a Fuel-Driven Transient-Esterification Network*

Signal transduction in living systems is the conversion of information into a chemical change, and is the principal process by which cells communicate. In nature, these functions are encoded in non-equilibrium (bio)chemical reaction networks (CRNs) controlled by enzymes. However, man-made catalytically controlled networks are rare. We incorporated catalysis into an artificial fuel-driven out-of-equilibrium CRN, where the forward (ester formation) and backward (ester hydrolysis) reactions are controlled by varying the ratio of two organocatalysts: pyridine and imidazole. This catalytic regulation enables full control over ester yield and lifetime. This fuel-driven strategy was expanded to a responsive polymer system, where transient polymer conformation and aggregation are controlled through fuel and catalyst levels. Altogether, we show that organocatalysis can be used to control a man-made fuel-driven system and induce a change in a macromolecular superstructure, as in natural non-equilibrium systems.

pH-Responsive Polyketone/5,10,15,20-Tetrakis-(Sulfonatophenyl)Porphyrin Supramolecular Submicron Colloidal Structures

In this work, we prepared color-changing colloids by using the electrostatic self-assembly approach. The supramolecular structures are composed of a pH-responsive polymeric surfactant and the water-soluble porphyrin 5,10,15,20-tetrakis-(sulfonatophenyl)porphyrin (TPPS). The pH-responsive surfactant polymer was achieved by the chemical modification of an alternating aliphatic polyketone (PK) via the Paal–Knorr reaction with N-(2-hydroxyethyl)ethylenediamine (HEDA). The resulting polymer/dye supramolecular systems form colloids at the submicron level displaying negative zeta potential at neutral and basic pH, and, at acidic pH, flocculation is observed. Remarkably, the colloids showed a gradual color change from green to pinky-red due to the protonation/deprotonation process of TPPS from pH 2 to pH 12, revealing different aggregation behavior.

Redox-Mediated, Transient Supramolecular Charge-Transfer Gel and Ink

Unprecedented spatiotemporal control exhibited by natural systems has aroused interest in the construction of its synthetic mimics. Cytoskeleton proteins utilize fuel-driven dissipative self-assembly to temporally regulate cell shape and motility. Until now, synthetic efforts have majorly contributed to fundamental strategies; however, temporally programmed functions are rarely explored. Herein, we work toward alleviating this scenario by using a charge-transfer (CT) based supramolecular polymer that undergoes structural changes under the effect of a redox fuel. The structural changes in supramolecular assembly amplify into observable macroscopic and material property changes. As a result, we achieve transient chemochromism,  a self-erasing ink and self-regenerating hydrogel, whose temporal profile can be regulated by varying the concentrations of the chemical cues (fuel and enzyme). The redox-mediated transient functions in the CT based supramolecular polymer pave way to create next-generation active, adaptive, and autonomous smart materials.

Light-powered and transient peptide two-dimensional assembly driven by trans-to-cis isomerization of azobenzene side chains

A 2D dissipative system is initiated by photo-powered trans-to-cis isomerization of azobenzene, which usually results in the collapse of ordered assemblies.

Structure-Property Effects in the Generation of Transient Aqueous Benzoic Acid Anhydrides by Carbodiimide Fuels

The design of dissipative systems, which operate out-of-equilibrium by consuming chemical fuels, is challenging. As yet, there are a few examples of privileged fuel chemistries that can be broadly applied in abiotic systems in the same way that ATP hydrolysis is exploited throughout biochemistry. The key issue is that designing nonequilibrium systems is inherently about balancing the relative rates of coupled reactions. The use of carbodiimides as fuels to generate transient aqueous carboxylic anhydrides has recently been used in examples of new nonequilibrium materials and supramolecular assemblies. Here, we explore the kinetics of formation and decomposition of a series of benzoic anhydrides generated from the corresponding acids and EDC under typical conditions (EDC = N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride). The reactions can be described by a simple mechanism that merges known behavior for the two processes independently. Structure-property effects in these systems are dominated by differences in the anhydride decomposition rate. The kinetic parameters allow trends in concentration-dependent properties to be simulated, such as reaction lifetimes, peak anhydride concentrations, and yields. For key properties, there are diminishing returns with the addition of increasing amounts of fuel. These results should provide useful guidelines for the design of functional systems making use of this chemistry.

Multivariate statistical analysis of chemical and electrochemical oscillators for an accurate frequency selection

The effect of experimental parameters on the frequency of chemical oscillators has been systematically studied since the first observations of clock reactions. The approach is mainly based on univariate changes in one specific parameter while others are kept constant. The frequency is then monitored and the effect of each parameter is discussed separately. This type of analysis, however, does not take into account the multiple interactions among the controllable parameters and the synergic responses on the oscillation frequency. We have carried out a multivariate statistical analysis of chemical (BZ-ferroin catalyzed reaction) and electrochemical (Cu/Cu₂O cathodic deposition) oscillators and identified the contributions of the experimental parameters on frequency variations. The BZ reaction presented a strong dependence on the initial concentration of sodium bromate and temperature, resulting in a frequency increase. The concentration of malonic acid, the organic substrate, affects the system but with lower intensity compared with the combination of sodium bromate and temperature. On the other hand, the Cu/Cu₂O electrochemical oscillator was shown to be less sensitive to changes in the temperature. The applied current density and pH were the two parameters which most perturbed the system. Interestingly, the frequency behaved nonmonotonically with a quadratic dependence. The multivariate analysis of both oscillators exhibited significant differences - while the homogenous oscillator displayed a linear dependence with the factors, the heterogeneous one revealed a more complex dependence with quadratic terms. Our results may contribute, for instance, in the synthesis of self-organized materials in which an accurate frequency selection is required and, depending on its value, different physicochemical properties are obtained.

Controllable hierarchical self-assembly of porphyrin-derived supra-amphiphiles

Control of self-assembly is significant to the preparation of supramolecular materials and illustration of diversities in either natural or artificial systems. Supra-amphiphiles have remarkable advantages in the construction of nanostructures but control of shape and size of supramolecular nanostructures is still a great challenge. Here, we fabricate a series of supra-amphiphiles by utilizing the recognition motifs based on a heteroditopic porphyrin amphiphile and its zinc complex. These porphyrin amphiphiles can bind with a few guests including Cl^-, coronene, C₆₀, 4,4'-bipyridine and 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine, which are further applied to facilitate the controllable self-assembly. Addition of these guests result in the formation of various supra-amphiphiles with well-defined structures, thus induce the generation of different aggregates. A diverse of aggregation morphologies including nanospheres, nanorods, films, spheric micelles, vesicles and macrowires are constructed upon the influence of specific complexation, which highlights the present work with abundant control on the shapes and dimensions of self-assemblies.

Residue-Specific Solvation-Directed Thermodynamic and Kinetic Control over Peptide Self-Assembly with 1D/2D Structure Selection

Understanding the self-organization and structural transformations of molecular ensembles is important to explore the complexity of biological systems. Here, we illustrate the crucial role of cosolvents and solvation effects in thermodynamic and kinetic control over peptide association into ultrathin Janus nanosheets, elongated nanobelts, and amyloid-like fibrils. We gained further insight into the solvation-directed self-assembly (SDSA) by investigating residue-specific peptide solvation using molecular dynamics modeling. We proposed the preferential solvation of the aromatic and alkyl domains on the peptide backbone and protofibril surface, which results in volume exclusion effects and restricts the peptide association between hydrophobic walls. We explored the SDSA phenomenon in a library of cosolvents (protic and aprotic), where less polar cosolvents were found to exert a stronger influence on the energetic balance at play during peptide propagation. By tailoring cosolvent polarity, we were able to achieve precise control of the peptide nanostructures with 1D/2D shape selection. We also illustrated the complexity of the SDSA system with pathway-dependent peptide aggregation, where two self-assembly states ( i.e., thermodynamic equilibrium state and kinetically trapped state) from different sample preparation methods were obtained.

Redox and pH responsive polymeric vesicles constructed from a water-soluble pillar[5]arene and a paraquat-containing block copolymer for rate-tunable controlled release

Herein, for rate-tunable controlled release, pH and redox dual responsive polymeric vesicles were constructed based on host-guest interaction between a water soluble pillar[5]arene (WP5) and a paraquat-containing block copolymer (BCP) in water. The yielding polymeric vesicles can be further applied in the controlled release of a hydrophilic model drug, doxorubicin hydrochloride (DOX). The drug release rate is regulated depending on the type of single stimulus or the combination of two stimuli. Meanwhile, DOX-loaded polymeric vesicles present anticancer activity in vitro comparable to free DOX under the studied conditions, which may be important for applications in the therapy of cancers as a controlled-release drug carrier.

pH clock instructed transient supramolecular peptide amphiphile and its vesicular assembly

A pH clock directed transient supramolecular peptide amphiphile and its vesicular assembly using ternary complexation of cucurbit[8]uril is displayed.

Dissipative Self-Assembly Driven by the Consumption of Chemical Fuels

Dissipative self-assembly leads to structures and materials that exist away from equilibrium by continuously exchanging energy and materials with the external environment. Although this mode of self-assembly is ubiquitous in nature, where it gives rise to functions such as signal processing, motility, self-healing, self-replication, and ultimately life, examples of dissipative self-assembly processes in man-made systems are few and far between. Herein, recent progress in developing diverse synthetic dissipative self-assembly systems is discussed. The systems reported thus far can be categorized into three classes, in which: i) the fuel chemically modifies the building blocks, thus triggering their self-assembly, ii) the fuel acts as a template interacting with the building blocks noncovalently, and iii) transient states are induced by the addition of two mutually exclusive stimuli. These early studies give rise to materials that would be difficult to obtain otherwise, including hydrogels with programmable lifetimes, vesicular nanoreactors, and membranes exhibiting transient conductivity.

ATP-Driven Temporal Control over Structure Switching of Polymeric Micelles

An adenosine triphosphate (ATP)-fueled micellar system in the out-of-equilibrium state was constructed based on 4,5-diamino-1,3,5-triazine (DAT)-containing block copolymer. The block copolymer self-assembled into spherical micelles in equilibrium steady state at pH higher than its p K_a. The pendant DAT residues in protonated form acted as ATP catchers via hydrogen bonding and electrostatic interactions. Activated by ATP fuel, the polymeric micelles spontaneously disrupted into small aggregates of ATP/polymer hybrid complexes. The consumption of ATP energy via the enzymatic hydrolysis led to dissociation of the complexes and reversible formation of polymeric micelles. A transient self-assembly cycle, in which the assembly underwent autonomous division-fusion motion, was created using ATP fuel and enzyme; the switching of assembly structure was sustained by continuous supply of ATP fuel. This DAT-containing block copolymer have good biocompatibility, and drug-loaded micelles display ATP-responsive release behavior. It is expected that this ATP-fueled supramolecular assembly system will provide a functional platform for biomimic chemistry and therapeutic applications.

A transient self-assembling self-replicator

Developing physical models of complex dynamic systems showing emergent behaviour is key to informing on persistence and replication in biology, how living matter emerges from chemistry, and how to design systems with new properties. Herein we report a fully synthetic small molecule system in which a surfactant replicator is formed from two phase-separated reactants using an alkene metathesis catalyst. The replicator self-assembles into aggregates, which catalyse their own formation, and is thermodynamically unstable. Rather than replicating until the reactants are fully consumed, the metastable replicator is depleted in a second metathesis reaction, and closed system equilibrium is eventually reached. Mechanistic experiments suggest phase separation is responsible for both replicator formation and destruction.

Fuel-Driven Dissipative Self-Assembly of a Supra-Amphiphile in Batch Reactor

Dissipative self-assembly is an intriguing but challenging research topic in chemistry, materials science, physics, and biology because most functional self-assembly in nature, such as the organization and operation of cells, is actually an out-of-equilibrium system driven by energy dissipation. In this article, we successfully fabricated an I₂-responsive supra-amphiphile by a PEGylated poly(amino acid) and realize its dissipative self-assembly in batch reactor by coupling it with the redox reaction between NaIO₃ and thiourea, in which I₂ is an intermediate product. The formation and dissipative self-assembly of the supra-amphiphile can be repeatedly initiated by adding the mixture of NaIO₃ and thiourea, which herein acts as "chemical fuel", while the lifetime of the transient nanostructures formed by the dissipative self-assembly is easily tuned by altering thiourea concentration in the "chemical fuel". Furthermore, as an application demo, the dissipative self-assembly of the supra-amphiphile is examined to control dispersion of multiwalled carbon nanotubes in water, exhibiting a good performance of organic pollutant removal.

Dissipative out-of-equilibrium assembly of man-made supramolecular materials

The use of dissipative self-assembly driven by chemical reaction networks for the creation of unique structures is gaining in popularity. In dissipative self-assembly, precursors are converted into self-assembling building blocks by the conversion of a source of energy, typically a photon or a fuel molecule. The self-assembling building block is intrinsically unstable and spontaneously reverts to its original precursor, thus giving the building block a limited lifetime. As a result, its presence is kinetically controlled, which gives the associated supramolecular material unique properties. For instance, formation and properties of these materials can be controlled over space and time by the kinetics of the coupled reaction network, they are autonomously self-healing and they are highly adaptive to small changes in their environment. By means of an example of a biological dissipative self-assembled material, the unique concepts at the basis of these supramolecular materials will be discussed. We then review recent efforts towards man-made dissipative assembly of structures and how their unique material properties have been characterized. In order to help further the field, we close with loosely defined design rules that are at the basis of the discussed examples.

From dynamic self-assembly to networked chemical systems

Although dynamic self-assembly, DySA, is a relatively new area of research, the past decade has brought numerous demonstrations of how various types of components - on scales from (macro)molecular to macroscopic - can be arranged into ordered structures thriving in non-equilibrium, steady states. At the same time, none of these dynamic assemblies has so far proven practically relevant, prompting questions about the field's prospects and ultimate objectives. The main thesis of this Review is that formation of dynamic assemblies cannot be an end in itself - instead, we should think more ambitiously of using such assemblies as control elements (reconfigurable catalysts, nanomachines, etc.) of larger, networked systems directing sequences of chemical reactions or assembly tasks. Such networked systems would be inspired by biology but intended to operate in environments and conditions incompatible with living matter (e.g., in organic solvents, elevated temperatures, etc.). To realize this vision, we need to start considering not only the interactions mediating dynamic self-assembly of individual components, but also how components of different types could coexist and communicate within larger, multicomponent ensembles. Along these lines, the review starts with the discussion of the conceptual foundations of self-assembly in equilibrium and non-equilibrium regimes. It discusses key examples of interactions and phenomena that can provide the basis for various DySA modalities (e.g., those driven by light, magnetic fields, flows, etc.). It then focuses on the recent examples where organization of components in steady states is coupled to other processes taking place in the system (catalysis, formation of dynamic supramolecular materials, control of chirality, etc.). With these examples of functional DySA, we then look forward and consider conditions that must be fulfilled to allow components of multiple types to coexist, function, and communicate with one another within the networked DySA systems of the future. As the closing examples show, such systems are already appearing heralding new opportunities - and, to be sure, new challenges - for DySA research.

Dissipative disassembly of colloidal microgel crystals driven by a coupled cyclic reaction network

A plethora of natural systems rely on the consumption of chemical fuel or input of external energy to control the assembly and disassembly of functional structures on demand. While dissipative assembly has been demonstrated, the control of structural breakdown using a dissipative cycle remains almost unexplored. Here, we propose and realize a dissipative disassembly process using two coupled cyclic reactions, in which protons mediate the interaction between the cycles. We show how an ordered colloidal crystal, can cyclically transform into a disordered state by addition of energy to a chemical cycle, reversibly activating a photoacid. This cycle is coupled to the colloidal assembly cycle via the exchange of protons, which in turn trigger charging of the particles. This system is an experimental realization of a cyclic reaction-assembly network and its principle can be extended to other types of structure formation.