Supramolecular Polymer Systems Research Articles

Polymer System Based on Polyethylene Glycol and TFE Telomers for Producing Films with Switchable Wettability.

Today a lot of attention is paid to the formation of thermosensitive systems for biomedical and industrial applications. The development of new methods for synthesis of such systems is a dynamically developing direction in chemistry and materials science. In this regard, this paper presents results of the studies of a new synthesized supramolecular polymer system based on polyethylene glycol and tetrafluoroethylene telomers. The films formed from the polymer substance have the property of switching wettability depending on temperature after heating activation. It has been established that the wettability changes at 60 °C. The contact angle of activated hydrophobic polymer film reaches 143°. Additionally, the system exhibits its properties regardless of the pH of the environment. Based on data obtained by the methods of infrared and x-ray photoelectron spectroscopy, differential thermal analysis and thermal analysis in conjunction with wettability and morphology, a model of the behavior of molecules in a polymer system was built that ensures switching of the hydrophilic/hydrophobic surface state. The resulting polymer system, as well as films based on it, can be used in targeted drug delivery, implantation surgery, as sensors, etc.

Supramolecular polymer-based gel fracturing fluid with a double network applied in ultra-deep hydraulic fracturing

A gel based on polyacrylamide, exhibiting delayed crosslinking characteristics, emerges as the preferred solution for mitigating degradation under conditions of high temperature and extended shear in ultralong wellbores. High viscosity/viscoelasticity of the fracturing fluid was required to maintain excellent proppant suspension properties before gelling. Taking into account both the cost and the potential damage to reservoirs, polymers with lower concentrations and molecular weights are generally preferred. In this work, the supramolecular action was integrated into the polymer, resulting in significant increases in the viscosity and viscoelasticity of the synthesized supramolecular polymer system. The double network gel, which is formed by the combination of the supramolecular polymer system and a small quantity of Zr-crosslinker, effectively resists temperature while minimizing permeability damage to the reservoir. The results indicate that the supramolecular polymer system with a molecular weight of (268–380) × 104 g/mol can achieve the same viscosity and viscoelasticity at 0.4 wt% due to the supramolecular interaction between polymers, compared to the 0.6 wt% traditional polymer (hydrolyzed polyacrylamide, molecular weight of 1078 × 104 g/mol). The supramolecular polymer system possessed excellent proppant suspension properties with a 0.55 cm/min sedimentation rate at 0.4 wt%, whereas the 0.6 wt% traditional polymer had a rate of 0.57 cm/min. In comparison to the traditional gel with a Zr-crosslinker concentration of 0.6 wt% and an elastic modulus of 7.77 Pa, the double network gel with a higher elastic modulus (9.00 Pa) could be formed only at 0.1 wt% Zr-crosslinker, which greatly reduced the amount of residue of the fluid after gel-breaking. The viscosity of the double network gel was 66 mPa s after 2 h shearing, whereas the traditional gel only reached 27 mPa s.

Pillar[5]arene-Based Fluorescent Supramolecular Polymers Without Conventional Chromophores.

Fluorescent supramolecular polymers have garnered significant attention due to their successful integration of supramolecular polymers and fluorescence, offering vast potential for applications in sensing, imaging, optoelectronics, and photonics. In this study, we present a novel supramolecular polymer based on P5-OH, derived from mono-substituted pillararene macrocycles. Notably, these formed supramolecular polymeric aggregates exhibit a prominent blue emission, representing a rare instance of fluorescent polymers devoid of conventional chromophores. Furthermore, through the modification of alkyl chain ending groups attached to pillar[5]arenes, slight shifts in the emission peak could be observed. This research expands the scope of functional supramolecular polymeric systems utilizing pillararenes, providing valuable insights for the design of innovative luminescent materials and optical devices.

Multi-supramolecular and double-network strategy improves rheological properties and oil displacement efficiency of polymers

In enhanced oil recovery (EOR), the application of polymer systems in harsh reservoir conditions is limited. This study conducted a proof-of-concept study of multi-supramolecular interactions and dual-network strategies, motivated by the desire to gain insights into the effectiveness of these higher-order self-assembled polymer flooding. Xanthan gum dual network supramolecular polymer (DN-HXG) system was obtained by multi-supramolecular cross-linking of polyacrylamide and xanthan gum, and compared with hydrophobic polyacrylamide/hydrophobic xanthan gum (HMPAM/MXG) mixture and polyacrylamide/xthan gum (HPAM/XG) mixture. The thickening and temperature and salt tolerance mechanisms of DN-HXG were analyzed by environmental scanning electron microscopy (ESEM), dynamic light scattering (DLS) and fluorescence spectra. The results show that the DN-HXG system has excellent viscoelastic and shear resistance. Due to the presence of multiple supramolecular interactions and rigid xanthan gum molecular chains, DN-HXG can withstand environments of more than 120 ℃ and 50 g/L salinity, which has good applicability in harsh reservoirs. In laboratory oil displacement experiments, DN-HXG shows obvious advantages in low-permeability core, and the recovery rate of DN-HXG is more than 20 % higher than that of conventional polymer. These experiments show that the strategies described can be applied to other synthetic polymers and biopolymers to improve their oil displacement properties.

Solvent-Directed Hierarchical Self-Assembly of Tetraphenylpyrazine-Cholesterol with Amplified Circularly Polarized Luminescence.

It is important to identify the effect of assembly and aggregation on the chirality transfer and energy transmission in supramolecular polymer system, since the unordered aggregation is insufficient to promote luminescence enhancement and chirality transfer, even causing the negative effect. Another key issue is to identify the solvent effect on hierarchically chiral self-assembly. Herein, we designed an AIE-core based building block, tetraphenylpyrazine-cholesterol (TPP-Chol), to explore how the solvent component influences chirality transfer and energy transmission of its aggregates and/or assemblies. Interestingly, the hierarchical assembly behavior was realized in the mixture of MeOH/CHCl3 highly dependent on the MeOH content. During the solvent-directed hierarchical assembly, the morphologic transformations, such as nanoribbons with a width of 150 nm, twisted nanoribbons with helical pitch of 420 nm, nanoribbon clusters, and microflowers with an average diameter of 5.5 μm, were realized with obvious chirality amplification for both circular dichroism (CD) and circularly polarized luminescence (CPL) measurements. The hierarchical assembly of TPP-Chol was also demonstrated by a time-dependent CD test. The work points out the complexity and dynamic of hierarchically chiral self-assembly regulated by the solvent effect, which would be helpful for the development of supramolecular materials with enhanced CPL performance and dynamic chirality.

Kinetic and Thermodynamic Aggregation of Coordinated Supramolecular Polymers with Quadruple Modulated Inversion of Circular Dichroism

AbstractSupramolecular chirality is the inherent property and the corresponding performance of aggregated materials in the supramolecular polymer (SP) system. It is an interesting but challenging issue to regulate the handedness direction of supramolecular chirality and achieve the circular dichroism (CD) inversion of chiral SP‐based aggregates, especially for the ones assembled from metal‐organic supramolecular polymer (MOSP) with great potential in asymmetric catalysis, chiral recognition, and chiroptical devices. Herein, a set of nanoaggregates coassembled from para‐pyridine imine‐linked cholesterol conjugate (pPMPCC) and various metal salts, using the cooperative interactions of metal‐ion coordination, van der Waals interaction and solvent polarity, is rationally designed and prepared. Interestingly, quadruple modulated supramolecular chirality inversion (SMCI) of MOSP‐based nanoaggregates is modulated by various metal ions (such as Co2+, Cu2+, Zn2+, Mn2+, and Bi3+) and their content, as well as the external stimuli like solvent effects, temperature, and ultrasound. This work provides a facile pathway to tune the helical self‐aggregation of metal‐organic complex systems with quadruple‐modulated CD inversion, which would be of great potential in asymmetric catalysis, chiral recognition, and sensing with dynamic supramolecular chirality.

Simulating Assembly Landscapes for Comprehensive Understanding of Supramolecular Polymer-Solvent Systems.

Complexity in supramolecular polymer systems arises from interactions between different components, including solvent molecules. By varying their concentration or temperature in such multicomponent systems, complex phenomena can occur such as thermally bisignate and dilution-induced assembly of supramolecular polymers. Herein, we demonstrate that both these phenomena emerge from the same underlying interaction mechanism between the components. As a model system, amide-decorated supramolecular polymers of porphyrins were investigated in combination with aliphatic alcohols as hydrogen-bond scavengers, and thermodynamic mass-balance models were applied to map the three-dimensional assembly landscapes. These studies unveiled that the interaction between hydrogen-bond scavengers and monomers is temperature-dependent and becomes dominant at high monomer concentrations. With these insights, we could exploit competitive monomer-alcohol interactions to prompt the dilution-induced assembly of various common monomers as well as bisignate assembly events. Moreover, kinetic insights were obtained by navigating through the assembly landscape. Similar to phase diagrams of covalent polymers, these assembly landscapes provide a comprehensive picture of supramolecular polymerizations, which helps to precisely regulate the system properties. The generality of this approach using assembly landscapes makes it relevant for any supramolecular system, and this enhanced control will open the door to build complex and functional supramolecular polymer systems.

Multistep sequence-controlled supramolecular polymerization by the combination of multiple self-assembly motifs

The precise sequence control of polymer chain is an important research topic of polymer chemistry. Although some methods such as iterative synthesis and supramolecular polymerization have been developed to fabricate sequence-controllable polymer, it is still a great challenge to consecutively prepare multiple supramolecular polymers with different sequence structures. In this work, through the reasonable utilization of assembly motifs, we integrated multiple host-guest recognitions and metal coordination interactions to prepare different sequence-controlled supramolecular polymers by a multistep assembly strategy. This research provides inspiration for the design and preparation of supramolecular polymers with different sequence structures.

A modular and efficient synthetic platform for the construction of supramolecular mono-telechelic polymers

Supramolecular telechelic polymers are intriguing macromolecular systems for the construction of complex supramolecular systems and responsive soft materials. In this work, we report a practical synthetic approach to preparing supramolecular mono-telechelic polymers with high efficiency and modularity. With a combination of in situ catalyst functionalization, ring-opening metathesis polymerization, and post-polymerization modification, a series of supramolecular mono-telechelic polymers with different supramolecular end-groups and sidechains are synthesized. Several selected examples are then discussed in detail to demonstrate their potential in constructing hierarchical supramolecular architectures, adaptive materials, and supramolecular biomaterials. It is highly anticipated that the synthetic approach reported here will provide rapid and controlled access to complex supramolecular polymeric systems with tailored functions.

The Contributions of Supramolecular Kinetics to Dynamics of Supramolecular Polymers.

Supramolecular polymers exhibit well-controlled dynamics with fascinating capacity for remodeling, self-healing, and stimuli-responsiveness. Supramolecular kinetics of non-covalent bonds is a dominant control handle among the relevant factors to tailor dynamics of supramolecular polymers. This Review focuses on elucidating how supramolecular kinetics dictates the polymer dynamics in supramolecular polymer systems. The ways to tailor supramolecular kinetics are firstly examined as prerequisites for structure-activity study of supramolecular polymers. We next discuss the role of supramolecular kinetics in supramolecular polymers under different polymer architectures by the combination of both of theoretical and experimental studies. Finally, we conclude by discussing the existing challenges and opportunities in the current studies.

Thermo‐responsive topological metamorphosis in covalent‐and‐supramolecular polymer architectures

AbstractTopological metamorphosis represents a powerful approach to modulate the properties of polymers. However, it still remains a major challenge to achieve the tunability of bulk mechanical properties via topological transformation in supramolecular polymer systems. Herein, we couple the covalent polymer and supramolecular polymer in a single system—referred to as covalent‐and‐supramolecular polymer (CSP)—to realize a thermo‐responsive macromolecular metamorphosis. The CSP is able to topologically switch from grafted polymer to cross‐linked network by taking advantage of synergistic dynamic covalent interactions and host–guest interactions. Benefiting from the topologically structural transformation, brittleness intrinsically evolves into toughness in our CSP architectures with minimum change of their molecular compositions from furan–maleimide to anthracene–maleimide linkers. Our work demonstrates that supramolecular polymers are a promising platform to design smart materials not only due to their inherent stimuli‐responsive properties but also because of their abilities in determining bulk mechanical properties of polymers with alterable topological structures.

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.

Visualizing molecular weights differences in supramolecular polymers

Issues of molecular weight determination have been central to the development of supramolecular polymer chemistry. Whereas relationships between concentration and optical features are established for well-behaved absorptive and emissive species, for most supramolecular polymeric systems no simple correlation exists between optical performance and number-average molecular weight (Mn). As such, the Mn of supramolecular polymers have to be inferred from various measurements. Herein, we report an anion-responsive supramolecular polymer [M1·Zn(OTf)2]n that exhibits monotonic changes in the fluorescence color as a function of Mn Based on theoretical estimates, the calculated average degree of polymerization (DPcal) increases from 16.9 to 84.5 as the monomer concentration increases from 0.08 mM to 2.00 mM. Meanwhile, the fluorescent colors of M1 + Zn(OTf)2 solutions were found to pass from green to yellow and to orange, corresponding to a red shift in the maximum emission band (λmax ). Therefore, a relationship between DPcal and λmax could be established. Additionally, the anion-responsive nature of the present system meant that the extent of supramolecular polymerization could be regulated by introducing anions, with the resulting change in Mn being readily monitored via changes in the fluorescent emission features.

Progress of albumin-polymer conjugates as efficient drug carriers

Abstract Albumin is a protein that has garnered wide attention in nanoparticle-based drug delivery of cancer therapeutics due to its natural abundance and unique cancer-targeting ability. The propensity of albumin to naturally accumulate in tumours, further augmented by the incorporation of targeting ligands, has made the field of albumin-polymer conjugate development a much pursued one. Polymerization techniques such as RAFT and ATRP have paved the path to incorporate various polymers in the design of albumin-polymer hybrids, indicating the advancement of the field since the first instance of PEGylated albumin in 1977. The synergistic combination of albumin and polymer endows manifold features to these macromolecular hybrids to evolve as next generation therapeutics. The current review is successive to our previously published review on drug delivery vehicles based on albumin-polymer conjugates and aims to provide an update on the progress of albumin-polymer conjugates. This review also highlights the alternative of exploring albumin-polymer conjugates formed via supramolecular, non-covalent interactions. Albumin-based supramolecular polymer systems provide a versatile platform for functionalization, thereby, holding great potential in enhancing cytotoxicity and controlled delivery of therapeutic agents.

Unconventional assemblies of bisacylhydrazones: The role of water for circularly polarized luminescence

AbstractUnderstanding the precise molecular arrangement of chiral supramolecular polymers is essential not only to comprehend complex superstructures like proteins and DNA but also for the development of next‐generation optoelectronic materials, including materials displaying high‐performance circularly polarized luminescence (CPL). Herein, we report the first chiral supramolecular polymer systems based on hydrazone–pyridinium conjugates comprising alkyl chains of different lengths, which afforded control of the apparent supramolecular chirality. Although supramolecular chirality is governed basically by the remote chiral centers of alkyl chains, helicity inversion was achieved by controlling the conditions under which the hydrazone building blocks underwent aggregation (i.e., solvent compositions or temperature). More importantly, the addition of water to the system led to aggregation‐induced hydrazone deprotonation, which resulted in a completely different self‐assembly behavior. Structural water molecules played an essential role, forming the assembly's channel‐like backbone, around which hydrazone molecules gathered as a result of hydrogen bonding interactions. Further co‐assembly of an achiral hydrazone luminophore with the given supramolecular polymer system allowed the fabrication of a novel CPL‐active hydrazone‐based material exhibiting a high maximum value for the photoluminescence dissymmetry factor of −2.6 × 10−2.

Design and Control of Perylene Supramolecular Polymers through Imide Substitutions.

The number and type of new supramolecular polymer (SMP) systems have increased rapidly in recent years. Some of the key challenges faced for these novel systems include gaining full control over the mode of self‐assembly, the creation of novel architectures and exploring functionality. Here, we provide a critical overview of approaches related to perylene‐based SMPs and discuss progress to exert control over these potentially important SMPs through chemical modification of the imide substituents. Imide substitutions affect self‐assembly behaviour orthogonally to the intrinsic optoelectronic properties of the perylene core, making for a valuable approach to tune SMP properties. Several recent approaches are therefore highlighted, with a focus on controlling 1) morphology, 2) H‐ or J‐ aggregation, and 3) mechanism of growth and degree of aggregation using thermodynamic and kinetic control. Areas of potential future exploration and application of these functional SMPs are also explored.

Construction of pillar[5]arene-based photochromic supramolecular polymeric system with tunable thermal bleaching rate

Naphthopyran is targeted as the photochromic material here due to its fast photo-sensitivity, high optical density, relative chemical structural simplicity, and its colorless degradation products are also important in commercial ophthalmic applications as variable transmission lenses. In this paper, we reported the synthesis and characterization of a new class of photochromic supramolecular system containing both pillar[5]arene subunit and naphthopyran moiety in the chemical structural backbone. Owing to the supramolecular host-guest interactions of pillar[5]arene/neutral nitrile molecular recognition motif, the designed molecules could be spontaneously self-assembled. Thus, the photochromic supramolecular system indicates an efficient photochromism with convenient tunable fading rate, providing a simple and versatile strategy to fabricate photochromic supramolecular system, as well as potential applications in advanced photo-responsive materials.

Chemoresponsive Supramolecular Polypseudorotaxanes with Infinite Switching Capability.

Chemoresponsive supramolecular systems with infinite switching capability are important for applications in recycled materials and intelligent devices. To attain this objective, here a chemoresponsive polypseudorotaxane is reported on the basis of a bis(p-phenylene)-34-crown-10 macrocycle (H) and a cyano-substituted viologen guest (G). H and G form a [2]pseudorotaxane (H⊃G) both in solution and in the solid state. Upon addition of AgSF6 , a polypseudorotaxane (denoted as [H⋅G⋅Ag]n ) forms as synergistically driven by host-guest complexation and metal-coordination interactions. [H⋅G⋅Ag]n depolymerizes into a [3]pseudorotaxane (denoted as H2 ⋅G⋅Ag2 ⋅acetone2 ) upon addition of H and AgSF6 , while it reforms with successive addition of G. The transformations between [H⋅G⋅Ag]n and H2 ⋅G⋅Ag2 ⋅acetone2 can be switched for infinite cycles, superior to the conventional chemoresponsive supramolecular polymeric systems with limited switching capability.

Chemoresponsive Supramolecular Polypseudorotaxanes with Infinite Switching Capability

AbstractChemoresponsive supramolecular systems with infinite switching capability are important for applications in recycled materials and intelligent devices. To attain this objective, here a chemoresponsive polypseudorotaxane is reported on the basis of a bis(p‐phenylene)‐34‐crown‐10 macrocycle (H) and a cyano‐substituted viologen guest (G). H and G form a [2]pseudorotaxane (H⊃G) both in solution and in the solid state. Upon addition of AgSF6, a polypseudorotaxane (denoted as [H⋅G⋅Ag]n) forms as synergistically driven by host–guest complexation and metal‐coordination interactions. [H⋅G⋅Ag]n depolymerizes into a [3]pseudorotaxane (denoted as H2⋅G⋅Ag2⋅acetone2) upon addition of H and AgSF6, while it reforms with successive addition of G. The transformations between [H⋅G⋅Ag]n and H2⋅G⋅Ag2⋅acetone2 can be switched for infinite cycles, superior to the conventional chemoresponsive supramolecular polymeric systems with limited switching capability.

Investigation of the Amide Linkages on Cooperative Supramolecular Polymerization of Organoplatinum(II) Complexes.

Cooperative supramolecular polymerization of π-conjugated compounds into one-dimensional nanostructures has received tremendous attentions in recent years. It is commonly achieved by incorporating amide linkages into the monomeric structures, which provide hydrogen bonds for intermolecular non-covalent complexation. Herein, the effect of amide linkages is elaborately studied, by comparing supramolecular polymerization behaviors of two structurally similar monomers with the same platinum(II) acetylide cores. As compared to the N-phenyl benzamide linkages, N-[(1S)-1-phenylethyl] benzamide linkages give rise to effective chirality transfer behaviors due to the closer distances between the chiral units and the platinum(II) acetylide core. They also provide stronger intermolecular hydrogen bonding strength, which consequently brings higher thermo-stability and enhanced gelation capability for the resulting supramolecular polymers. Supramolecular polymerization is further strengthened by varying the monomers from monotopic to ditopic structures. Hence, with the judicious modulation of structural parameters, the current study opens up new avenues for the rational design of supramolecular polymeric systems.