Dynamic Supramolecular Polymers Research Articles

Controlled Noncovalent Synthesis of Secondary Supramolecular Polymers.

Dynamic supramolecular polymers, with their functional similarities to classical covalent polymers and their adaptive and self-repairing nature reminiscent of biological assemblies, have emerged as highly promising systems for the design of smart soft materials. Recent advancements in mechanistic investigations and novel synthetic strategies, such as living supramolecular polymerization, have significantly enhanced our ability to control the primary structure of these supramolecular polymers. However, realizing their full functional potential requires expanding their topological diversity in a manner akin to classical polymers as well as achieving precise molecular organization at higher hierarchical levels of self-assembly. In this paper, we present a remarkable advancement in this field, introducing an unprecedented and controlled synthesis of secondary supramolecular polymers. Our innovative strategy combines chirality-controlled surface-catalyzed secondary nucleation and a bioinspired peptide design, effectively stabilizing higher-order assembly. Furthermore, by harnessing this stereoselective nucleation process, we demonstrate the successful synthesis of racemic supramolecular polymers featuring parallelly stacked conglomerate microstructures─a previously unreported topology in synthetic self-assembled systems. Additionally, we elucidate that the extent of secondary supramolecular polymers can be regulated by modulating the enantiomeric excess of the chiral monomers. Consequently, our study unveils new topologies that exhibit enhanced higher-order structural complexity in the realm of supramolecular polymers.

Dynamic Supramolecular Polymer Electrolyte to Boost Ion Transport Kinetics and Interfacial Stability for Solid‐State Batteries

AbstractThe key hurdle to the practical application of polymeric electrolytes in high‐energy‐density solid lithium‐metal batteries is the sluggish Li+ mobility and inferior electrode/electrolyte interfacial stability. Herein, a dynamic supramolecular polymer electrolyte (SH‐SPE) with loosely coordinating structure is synthesized based on poly(hexafluoroisopropyl methacrylate‐co‐N‐methylmethacrylamide) (PHFNMA) and single‐ion lithiated polyvinyl formal. The weak anti‐cooperative H‐bonds between the two polymers endow SH‐SPE with a self‐healing ability and improved toughness. Meanwhile, the good flexibility and widened energy gap of PHFNMA enable SH‐SPE with efficient ion transport and superior interfacial stability in high‐voltage battery systems. As a result, the as‐prepared SH‐SPE exhibits an ionic conductivity of 2.30 × 10−4 S cm−1, lithium‐ion transference number of 0.74, electrochemical stability window beyond 4.8 V, and tensile strength up to 11.9 MPa as well as excellent adaptability with volume change of the electrodes. In addition, no major electrolyte decomposition inside batteries made from SH‐SPE and LiNi0.8Mn0.1Co0.1O2 cathode can be observed in the in situ differential electrochemical mass spectrometry test. This study provides a new methodology for the macromolecular design of polymer electrolytes to address the interfacial issues in high‐voltage solid batteries.

Multivalent Design of Low-Entropy-Penalty Ion–Dipole Interactions for Dynamic Yet Thermostable Supramolecular Networks

Dynamic supramolecular networks are constantly accompanied by thermal instability. The fundamental reason is most reversible noncovalent bonds quickly decay at elevated temperatures and dissociate below 100 °C. Here, in this paper, we realize a reversible ion-dipole interaction with high-temperature stability exceeding 150 °C. The resultant supramolecular network can simultaneously possess mechanical strength of 1.32 MPa (14.8 times that of pristine material), dynamic self-healing capability, and a stable working temperature of up to 200 °C. From the prolonged characteristic relaxation time of 600 s even at 100 °C, our material represents one of the most thermally stable dynamic supramolecular polymers. These remarkable performances are achieved by using a new multivalent yet low-entropy-penalty molecular design. In this way, the noncovalent bond can reach a high enthalpy while minimizing the entropy-dominated thermal dissociations.

Dynamic Supramolecular Polymers Based on Zinc Bis(diorganophospate)s: Synthesis, Structure and Transformations in Solid State and Solutions.

The synthesis, structure and some properties of coordination polymers composed of linear zinc bis(diorganophospate)s (ZnDOPs) with a general formula of Zn[O2P(OR)2]2 (where R = CH3, C2H5, n-C4H9, or 2-ethylhexyl group) are described. Hybrid (co)polymers obtained by different procedures were characterized by means of powder XRD, DSC, SEM, TGA coupled with mass spectrometry of the evolved gases and rheological measurements, as well as FTIR and NMR techniques. The morphology, thermal transformations and solubility of ZnDOPs strongly depend on the type of organic substituent in the O2P(OR)2 ligands and the thermal history of the sample. Because of this, one can obtain highly crystalline rods, semicrystalline powders, as well as rubbery materials exhibiting a second-order transition below −50 °C. Polymeric chains formed by ZnDOPs undergo a reversible dissociation in polar organic solvents (e.g., methanol, DMSO), which allows for easy modification of their composition and physicochemical properties via a simple exchange of diorganophosphate anions. Some of the ZnDOPs were investigated as the latent curing agents for epoxides. On the basis of rheological and DSC studies, it is evident that ZnDOPs catalyze very effectively the cross-linking process within the 130–160 °C temperature range.

Molecular communications in complex systems of dynamic supramolecular polymers

Supramolecular polymers are composed of monomers that self-assemble non-covalently, generating distributions of monodimensional fibres in continuous communication with each other and with the surrounding solution. Fibres, exchanging molecular species, and external environment constitute a sole complex system, which intrinsic dynamics is hard to elucidate. Here we report coarse-grained molecular simulations that allow studying supramolecular polymers at the thermodynamic equilibrium, explicitly showing the complex nature of these systems, which are composed of exquisitely dynamic molecular entities. Detailed studies of molecular exchange provide insights into key factors controlling how assemblies communicate with each other, defining the equilibrium dynamics of the system. Using minimalistic and finer chemically relevant molecular models, we observe that a rich concerted complexity is intrinsic in such self-assembling systems. This offers a new dynamic and probabilistic (rather than structural) picture of supramolecular polymer systems, where the travelling molecular species continuously shape the assemblies that statistically emerge at the equilibrium.

Research data supporting: "Molecular communications in complex systems of dynamic supramolecular polymers"

Research data supporting: "Molecular communications in complex systems of dynamic supramolecular polymers"

Choline-Functionalized Supramolecular Copolymers: Toward Antimicrobial Activity against Streptococcus pneumoniae.

Dynamic binding events are key to arrive at functionality in nature, and these events are often governed by electrostatic or hydrophobic interactions. Synthetic supramolecular polymers are promising candidates to obtain biomaterials that mimic this dynamicity. Here, we created four new functional monomers based on the benzene-1,3,5-tricarboxamide (BTA) motif. Choline or atropine groups were introduced to obtain functional monomers capable of competing with the cell wall of Streptococcus pneumoniae for binding of essential choline-binding proteins (CBPs). Atropine-functionalized monomers BTA-Atr and BTA-Atr3 were too hydrophobic to form homogeneous assemblies, while choline-functionalized monomers BTA-Chol and BTA-Chol3 were unable to form fibers due to charge repulsion. However, copolymerization of BTA-Chol3 with non-functionalized BTA-(OH)3 yielded dynamic fibers, similar to BTA-(OH)3. These copolymers showed an increased affinity toward CBPs compared to free choline due to multivalent effects. BTA-based supramolecular copolymers are therefore a versatile platform to design bioactive and dynamic supramolecular polymers with novel biotechnological properties.

Controlling Exchange Pathways in Dynamic Supramolecular Polymers by Controlling Defects.

Supramolecular fibers composed of monomers that self-assemble directionally via noncovalent interactions are ubiquitous in nature, and of great interest in chemistry. In these structures, the constitutive monomers continuously exchange in-and-out the assembly according to a well-defined supramolecular equilibrium. However, unraveling the exchange pathways and their molecular determinants constitutes a nontrivial challenge. Here, we combine coarse-grained modeling, enhanced sampling, and machine learning to investigate the key factors controlling the monomer exchange pathways in synthetic supramolecular polymers having an intrinsic dynamic behavior. We demonstrate how the competition of directional vs. nondirectional interactions between the monomers controls the creation/annihilation of defects in the supramolecular polymers, from where monomers exchange proceeds. This competition determines the exchange pathway, dictating whether a fiber statistically swaps monomers from the tips or from all along its length. Finally, thanks to their generality, our models allow the investigation of molecular approaches to control the exchange pathways in these dynamic assemblies.

Stereoselective Primary and Secondary Nucleation Events in Multicomponent Seeded Supramolecular Polymerization.

Bioinspired, kinetically controlled seeded growth has been recently shown to provide length, dispersity, and sequence control on the primary structure of dynamic supramolecular polymers. However, command over the molecular organization at all hierarchical levels for the modulation of higher order structures of supramolecular polymers remains a formidable task. In this context, a surface-catalyzed secondary nucleation process, which plays an important role in the autocatalytic generation of amyloid fibrils and also during the chiral crystallization of small monomers, offers exciting possibilities for topology control in synthetic macromolecular systems by introducing secondary growth pathways compared to the usual primary nucleation-elongation process. However, mechanistic insights into the molecular determinants and driving forces for the secondary nucleation event in synthetic systems are not yet realized. Herein, we attempt to fill this dearth by showing an unprecedented molecular chirality control on the primary and secondary nucleation events in seed-induced supramolecular polymerization. Comprehensive kinetic experiments using in situ spectroscopic probing of the temporal changes of the monomer organization during the growth process provide a unique study to characterize the primary and secondary nucleation events in a supramolecular polymerization process. Kinetic analyses along with various microscopic studies further reveal the remarkable effect of stereoselective nucleation and seeding events on the (micro)structural aspects of the resulting multicomponent supramolecular polymers.

Structure and solvent effects on the stability of platinum(II) acetylide-based supramolecular polymers

Stability and stimuli-responsiveness are important parameters for dynamic supramolecular polymers. Herein we have found that, as compared to cyclic alkanes, linear alkanes facilitate to enhancement of solvo-, thermo-stability and photo-resistance for platinum(II) acetylide-based one-dimensional supramolecular polymers. It is primarily ascribed to low steric hindrance for linear alkane solvents, which tend to intercalate into the gap of the peripheral alkyl chains and thereby display higher Gibbs free energy for supramolecular polymerization processes. In addition, supramolecular polymers exhibit high thermo-stability by incorporating higher-order acenes to platinum(II) acetylide core unit, because of their stronger π-π stacking strength. Accordingly, the current study highlights the importance of structure and solvent parameters for the rational design of platinum(II) acetylide-based supramolecular polymers.

Transient dormant monomer states for supramolecular polymers with low dispersity

Temporally controlled cooperative and living supramolecular polymerization by the buffered release of monomers has been recently introduced as an important concept towards obtaining monodisperse and multicomponent self-assembled materials. In synthetic, dynamic supramolecular polymers, this requires efficient design strategies for the dormant, inactive states of the monomers to kinetically retard the otherwise spontaneous nucleation process. However, a generalized design principle for the dormant monomer states to expand the scope of precision supramolecular polymers has not been established yet, due to the enormous differences in the mechanism, energetic parameters of self-assembly and monomer exchange dynamics of the diverse class of supramolecular polymers. Here we report the concept of transient dormant states of monomers generated by redox reactions as a predictive general design to achieve monodisperse supramolecular polymers of electronically active, chromophoric or donor-acceptor, monomers. The concept has been demonstrated with charge-transfer supramolecular polymers with an alternating donor-acceptor sequence.

How to Determine the Role of an Additive on the Length of Supramolecular Polymers?

In polymer chemistry, modulation of sequence and control over chain length are routinely applied to alter and fine-tune the properties of covalent (co)polymers. For supramolecular polymers, the same principles underlying this control have not been fully elucidated up to this date. Particularly, rational control over molecular weight in dynamic supramolecular polymers is not trivial, especially when a cooperative mechanism is operative. We start this review by summarizing how molecular-weight control has been achieved in seminal examples in the field of supramolecular polymerizations. Following this, we propose to classify the avenues taken to control molecular weights in supramolecular polymerizations. We focus on dynamic cooperative supramolecular polymerization as this is the most challenging in terms of molecular weight control. We use a mass-balance equilibrium model to predict how the nature of the interaction of an additive B with the monomers and supramolecular polymers of component A affects the degree of aggregation and the degree of polymerization. We put forward a classification system that distinguishes between B acting as a chain capper, a sequestrator, a comonomer, or an intercalator. We also highlight the experimental methods applied to probe supramolecular polymerization processes, the type of information they provide in relation to molecular weight and degree of aggregation, and how this can be used to classify the role of B. The guidelines and classification delineated in this review to assess and control molecular weights in supramolecular polymers can serve to reevaluate exciting systems present in current literature and contribute to broaden the understanding of multicomponent systems.

Identifying and Tracking Defects in Dynamic Supramolecular Polymers.

A central paradigm of self-assembly is to create ordered structures starting from molecular monomers that spontaneously recognize and interact with each other via noncovalent interactions. In recent years, great efforts have been directed toward perfecting the design of a variety of supramolecular polymers and materials with different architectures. The resulting structures are often thought of as ideally perfect, defect-free supramolecular fibers, micelles, vesicles, etc., having an intrinsic dynamic character, which are typically studied at the level of statistical ensembles to assess their average properties. However, molecular simulations recently demonstrated that local defects that may be present or may form in these assemblies, and which are poorly captured by conventional approaches, are key to controlling their dynamic behavior and properties. The study of these defects poses considerable challenges, as the flexible/dynamic nature of these soft systems makes it difficult to identify what effectively constitutes a defect and to characterize its stability and evolution. Here, we demonstrate the power of unsupervised machine-learning techniques to systematically identify and compare defects in supramolecular polymer variants in different conditions, using as a benchmark 5 Å resolution coarse-grained molecular simulations of a family of supramolecular polymers. We show that this approach allows a complete data-driven characterization of the internal structure and dynamics of these complex assemblies and of the dynamic pathways for defects formation and resorption. This provides a useful, generally applicable approach to unambiguously identify defects in these dynamic self-assembled materials and to classify them based on their structure, stability, and dynamics.

Multivalent Ultrasensitive Interfacing of Supramolecular 1D Nanoplatforms.

Multivalent display on linear platforms is used by many biomolecular systems to effectively interact with their corresponding binding partners in a dose-responsive and ultrasensitive manner appropriate to the biological system at hand. Synthetic supramolecular multivalent displays offer a matching approach for the modular and bottom-up construction and systematic study of dynamic 1D materials. Fundamental studies into multivalent interactions between such linear, 1D materials have been lacking because of the absence of appropriate modular nanoplatforms. In this work we interfaced two synthetic multivalent linear nanoplatforms based on a dynamic supramolecular polymer, formed by hybrid discotic-oligonucleotide monomers, and a series of complementary DNA-duplex-based multivalent ligands, also with appended short oligonucleotides. The combination of these two multivalent nanoplatforms provides for the first time entry to study multivalent effects in dynamic 1D systems, of relevance for the conceptual understanding of multivalency in biology and for the generation of novel multivalent biomaterials. Together the two nanoscaffolds provide easy access to libraries of multivalent ligands with tunable affinities. The DNA scaffold allows for exact control over valency and spatial ligand distribution, and the discotic supramolecular polymer allows for dynamic adaptation and control over receptor density. The interaction between the two nanoplatforms was studied as a function of ligand interaction strength, valency, and density. Usage of the enhancement parameter β allowed quantification of the effects of ligand valency and affinity. The results reveal a generalized principle of additive binding increments. Receptor density is shown to be crucially and nonlinearly correlated to complex formation, leading to ultrasensitive responses. The results reveal that, not unlike biomolecular signaling, high density multivalent display of receptors is crucial for functionally increased affinities.

Molecular Tweezer/Guest Complexation with the Participation of Hydrogen Bonds: Toward the Formation of Orthogonal Supramolecular Polymers

AbstractDevelopment of well‐ordered supramolecular assemblies via the biomimetic orthogonal principle has aroused significant attention in recent years. To attain this objective, the elaborate choice of fundamental building blocks, together with the deep insight into mutual interplay among various non‐covalent forces, are of vital importance. Herein, a novel molecular tweezer/guest recognition motif with enhanced binding affinity has been established, by virtue of the formation of intermolecular N−H−N hydrogen bonds. The non‐covalent complexation persists even with the presence of ureidopyrimidinone hydrogen bonding motifs, which facilitate the fabrication of dynamic supramolecular polymers via orthogonal self‐assembly. The study is valuable for designing synthetic supramolecular systems with a higher level of complexity.

What Controls the Structure and the Linear and Nonlinear Rheological Properties of Dense, Dynamic Supramolecular Polymer Networks?

We investigated a series of telechelic polyisobutylenes, previously shown to exhibit self-healing, by means of small-angle X-ray scattering and rheology. All samples form a dense, dynamic network of interconnected micelles resulting from aggregation of the functional groups and leading to viscoelastic behavior. The dynamic character of this network manifests itself in the appearance of terminal flow at long time scales. While the elastic properties are distinctly molecular weight dependent, the terminal relaxation time is controlled by the functional end groups. The yielding properties under large deformation during startup shear experiments can be understood by a model of stress activation of the dynamic bonds. Stress relaxation experiments help to separate the nonlinear response into two contributions: a fast collapse of the network and a slow relaxation, happening on the time scale of the terminal relaxation. The latter is also known to control self-healing of the collapsed structure.

Mechano- and Thermoresponsive Photoluminescent Supramolecular Polymer.

Mechanoresponsive luminescent (MRL) materials change their emission color upon application of external forces. Many dyes with MRL behavior are known, but they normally do not display useful mechanical properties. Here, we introduce a new approach to overcome this problem, which relies on combining MRL compounds with the concept of supramolecular polymerization. As a first embodiment, a cyano-substituted oligo(p-phenylenevinylene), whose MRL behavior is associated with different solid-state assemblies, was derivatized with two ureido-4-pyrimidinone groups, which support the formation of a dynamic supramolecular polymer. The new material displays the thermomechanical characteristics of a supramolecular polymer glass, offers three different emission colors in the solid state, and exhibits both MRL and thermoresponsive luminescent behavior.

Optically responsive supramolecular polymer glasses.

The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible.

A dynamic supramolecular polymer with stimuli-responsive handedness for in situ probing of enzymatic ATP hydrolysis.

Design of artificial systems, which can respond to fluctuations in concentration of adenosine phosphates (APs), can be useful in understanding various biological processes. Helical assemblies of chromophores, which dynamically respond to such changes, can provide real-time chiroptical readout of various chemical transformations. Towards this concept, here we present a supramolecular helix of achiral chromophores, which shows chiral APs responsive tunable handedness along with dynamically switchable helicity. This system, composing of naphthalenediimides with phosphate recognition unit, shows opposite handedness on binding with ATP compared with ADP or AMP, which is comprehensively analysed with molecular dynamic simulations. Such differential signalling along with stimuli-dependent fast stereomutations have been capitalized to probe the reaction kinetics of enzymatic ATP hydrolysis. Detailed chiroptical analyses provide mechanistic insights into the enzymatic hydrolysis and various intermediate steps. Thus, a unique dynamic helical assembly to monitor the real-time reaction processes via its stimuli-responsive chiroptical signalling is conceptualized.

Phase transitions in the assembly of multivalent signalling proteins

Cells are organized on length scales ranging from Angstroms to microns. However, the mechanisms by which Angstrom-scale molecular properties are translated to micron-scale macroscopic properties are not well understood. Here we show that interactions between diverse, synthetic multivalent macromolecules (including multi-domain proteins and RNA) produce sharp, liquid-liquid demixing phase separations, generating micron-sized liquid droplets in aqueous solution. This macroscopic transition corresponds to a molecular transition between small complexes and large, dynamic supramolecular polymers. The concentrations needed for phase transition are directly related to valency of the interacting species. In the case of the actin regulatory protein, neuronal Wiskott-Aldrich Syndrome Protein (N-WASP) interacting with its established biological partners Nck and phosphorylated nephrin1, the phase transition corresponds to a sharp increase in activity toward the actin nucleation factor, Arp2/3 complex. The transition is governed by the degree of phosphorylation of nephrin, explaining how this property of the system can be controlled to regulatory effect by kinases. The widespread occurrence of multivalent systems suggests that phase transitions are likely used to spatially organize and biochemically regulate information throughout biology.