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.

Stimuli-responsive actuating hydrogels, with “soft and wet” state, are most important intelligent materials, which have been widely applied in more and more fields. However, the natural isotropic structure and high water-content of hydrogels leads to relatively simple actuating mode and weak mechanical performance respectively, which severely limit further applications of actuating hydrogels. To solve these problems, this study has developed a new actuating hydrogel with skin-mimetic anisotropic structure. Based on supramolecular interaction, monolayer MXene nanosheets can be loaded on the surface of silk-textile that can be embedded in the N-isopropylacrylamide (NIPAM) precursor solution to obtain as-prepared skin-mimetic anisotropic hydrogel (SMAH) with MXene-loaded silk-textile/poly(N-isopropylacrylamide) (PNIPAM) composite hydrogel layer and the pure PNIPAM hydrogel layer. First of all, the MXene-loaded silk-textile layer of the SMAH (just like the epidermis layer of the skin) not only can provide high strength for powerful actuating force, but also can be embedded into the PNIPAM layer (just like the dermis layer of the skin) to obtain anisotropic structure for various programmable complex actuation. Furthermore, the SMAH can achieve remotely-controlled near-infrared light (NIR)-responsive fast actuation owing to the high-efficiency of photothermal-conversion caused by the MXene-loaded silk-textile. As a result, this SMAH has been designed for several intelligent biomimetic devices with programmable complex, powerful (it can lift up ≥ 60 mass times of itself) and fast (71o/s of average bending speed) actuations under remotely-controlled NIR-irradiation, including biomimetic “claw”, “snake” and even “octopus”. This study provides a skin-like anisotropic intelligent actuating hydrogel for biomimetic deformations and movements, which also will inspire the new research of other smart materials and devices.

Abstract not available

Cholesterol is a rigid, crystalline, non-polar natural substance that exists in animal blood and cell membranes. Some of its derivatives are known to form ordered liquid crystalline mesophases under suitable conditions. In this work, we carefully examined the influence of cholesterol substitution on the characteristics of 3,4-ethylenedioxythiophene (EDOT-MA-cholesterol) and its corresponding polymer poly(3,4-ethylenedioxythiophene) (PEDOT-MA-cholesterol) synthesized by both chemical and electrochemical polymerization. We found evidence for an ordered lamellar (smectic-like) structure in the EDOT-MA-cholesterol monomer by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction techniques. The ordered phase was observed to form on cooling from the isotropic melt at about 80 °C. Due to the insulating and bulky cholesterol side group on the EDOT monomer, we found that there was a maximum charge density for electrodeposition at ∼ 0.155 C.cm−2. A series of electrodepositions were performed from 0 to 0.155 C.cm−2 for probing the change of the charge transport with more charges used for the electrodeposition. We found that the impedance increased in the high-frequency range (above 104 Hz) and decreased in the low-frequency range (below 102 Hz). Three equivalent circuit models were proposed for fitting impedance data at different charge densities for a better understanding of the film growth process. The suppressed cyclic voltammogram (CV) of PEDOT-MA-cholesterol showed that the charge storage capability was essentially eliminated in the thickest films. The limited doping of the films was corroborated by their diminished electrochromic behavior, polaron-dominating absorption in UV-vis, overoxidized S 2p X-ray Photoelectron Spectroscopy (XPS) signal of electrodeposited films, and proton Nuclear Magnetic Resonance (1H NMR) of chemically polymerized samples. Dense film morphologies were confirmed by scanning electron microscopy (SEM). Grazing incident X-ray diffraction (GIWAXS) indicated the disrupted stacking of conjugated chains, which correlated with the decreased conductivity of the PEDOT-MA-cholesterol films. The measurement of the electrical conductivity gave a value of around 3.30 × 10−6 S.cm−1 which is about six orders of magnitude lower than has been seen in PEDOT (∼3 S.cm-1).

A fast iterative growth method is reported to prepare monodisperse polymers assisted by a cyclization technique. This novel method uses a di-functional and a tri-functional compounds as monomer pairs. The di-functional monomer is designed to have an azide and a hydroxyl end groups, while the tri-functional monomer is designed to have an alkyne and a sym-dibenzo-1,5-cyclooctadiene-3,7-diyne containing two strained alkynes. One iterative cycle of this novel method is composed by four step reactions. First, the self-accelerating double-strain-promoted azide-alkyne click reaction is used to couple two monomers/oligomers having an azide and a hydroxyl end group pairs with one tri-functional monomer by reacting the azide and strained alkyne groups. This coupling reaction increases chain length and produces an elongated oligomers having two hydroxyl end groups and one alkyne group in the middle position of main-chain. Second, the esterification between anhydride and hydroxyl is used to modify the hydroxyl end groups to endow the elongated oligomers with two azide end groups. Third, copper(I)-catalyzed azide-alkyne click reaction is then used to ring-close the elongated oligomers by reacting the middle alkyne and one terminal azide groups to prepare a tadpole-shaped oligomers with one azide end group. Fourth, the 2,3-dichloro-5,6-dicyano-p-benzoquinone oxidized deprotection reaction is used to cleave the preset methoxybenzyl ether bond in the ring of the tadpole-shaped oligomers and rebuild an azide and a hydroxyl end group pairs for the elongated oligomers. The repetition of above iterative cycle can synthesize the monodisperse polymers with a fast chain-growth manner of 2n+1-1.

Hybrid nanoarchitectures where inorganic nanoparticles are added into a polymer matrix can present superior characteristics and unique synergetic effects. However, the homogeneously structured and monodispersed hybrid film has been a critical challenge because of the intrinsic incompatibility of hydrophobic nanoparticles and hydrophobic polymers. This review focuses on hierarchically hybrid nanoarchitectures of polymers and nanoparticles by electrochemical approaches. Of many methods, the use of electrochemically bottom-up in situ synthesis can prepare the controlled layered and hybrid formations of polymers and nanoparticles. The advantages are film-forming ability from very dilute solutions of nanoparticles and polymers, and covalently cross-linked structural stability. The electrochemical approach has provided highly predicted functions and performances for applications mostly studied including sensor, catalysis, and optoelectric relatives. With these in hand, electrochemically engineered hybrid nanoarchitectures of polymers and nanoparticles hold promise for the fabrication of hierarchically ordered materials on hardly or flexibly conductive substrates with rational scales and dimensions.

Blackberry structure is a type of universal, stable, porous, single layered, hollow, spherical supramolecular structure with sizes from tens to hundreds of nanometers self-assembled by various macroions (1–6 nm-size) in dilute solutions of water or other polar solvents. This self-assembly process is driven by counterion-mediated attraction, and merely requires ions to be large enough and moderately charged. The blackberry structures possess important features including their spontaneous and reversible self-assembly with tunable assembly sizes, capability of selectively segregating counterions, permeability to small counterions and molecules, self-recognition, as well as chiral recognition and selection. Considering such simple requirements for the self-assembly process and the mentioned features, and the availability of various macroions on the prebiotic earth, we will discuss about the possible role of blackberry structures as a compartmentalizing system in the origin of life concentrating the precursors and preparing proper conditions for the reaction to synthesize building blocks of early lives. We also speculate that they could have played a key role in the evolution of homochiral biological systems by intensifying the small enantiomeric imbalance, that might have existed on the prebiotic Earth.

In 1977 Chandrasekhar laboratory reported the first examples of a new class of thermotropic liquid crystals self-organized from planar disc-like molecules substituted with alkyl groups. X-ray analysis demonstrated that these disc-like molecules stack on top of each other at irregular spacing in columns located in the paraffin melt of their alkyl groups. These supramolecular columns self-organize in a hexagonal array defined as the new thermotropic discotic or columnar hexagonal liquid crystal phase. This new thermotropic liquid crystal phase has translational periodicity in two dimensions and liquid-like disorder in the third one, along the column axis. In 2002 Bushby and Lozman dedicated a brief review article to the 25 anniversary of discotic liquid crystals. This review also included a brief discussion of supramolecular discs and columns self-organized from self-assembling dendrons and dendrimers. The current publication is not another review but a brief perspective on new liquid crystal phases self-organized from dendronized rigid planar and conformationally flexible discs as well as from crown-like molecules. Crown-like molecules are the most stable conformation of a transient unstable disc. All dendronized disc-like and crown molecules adopt a crown conformation that self-assemble helical columns and spherical helices. A large diversity of new liquid crystalline phases self-organize from these helical columns and spherical helices. They include helical columnar hexagonal phases from crowns and from supramolecular spheres, Frank-Kasper A15 (known as cubic phase of space group Pm3¯n), σ phase (also known as tetragonal of space group P42/mnm), 12-fold quasi liquid crystals (QLC) and supramolecular orientational memory (SOM) derived complex bundles of supramolecular columnar hexagonal arrays that are not yet completely elucidated. The impact of Chandrasekhar on the discovery of self-assembling dendrons and dendrimers via his biaxial nematic liquid crystal concept will also be discussed. This perspective is dedicated to the 45 anniversary of the discovery of discotic liquid crystals and to the memory of Professor Sivaramakrishna Chandrasekhar, a modest, respectful and great scientist.

A shear rheometer requiring only 2 mg of sample was recently developed as mgRheo. No additional sample amount more than for typical chemical characterizations would be required. With this setup, various kinds of soft matter with limited yields can now be screened for their viscoelastic properties. This mgRheo is also friendly to advanced purification techniques with low yields of purer materials. It would facilitate us in studying the dynamics and rheology beyond the entangled linear polymers, which have been difficult to study due to the limited sample amount.

Flory-Huggins (FH) theory is foundational to understanding macro-phase separation in polymer solutions; however, its predictions often quantitatively disagree with experiment. Recent machine-learning (ML) methods have generated predictive models of phase behavior across a broad range of chemistries and state variables with uncertainty comparable to experiment, but they lack interpretability. In this work, we develop several hybrid frameworks that combine Flory-Huggins theory with ML to (i) further improve interpolation and extrapolation with less experimental data, as well as (ii) provide interpretability of the ML model. Using the well-studied binodal of polystyrene-cyclohexane as a case study, we compare data-derived ML models to hybrid models where the prediction is confined by a theoretical expression (theory-constrained model), or the feature vector input incorporates theoretical expressions (theory-informed model). Even though Flory-Huggins theory is imperfect, its incorporation improves performance under data sparse situations, such as when only 2 or 3 molecular masses are in the training set. However, neither approach to integrate theory provides advantages in accuracy or computational efficiency when greater coverage of the parameter space or quantities of experimental data are available, indicating that the greatest impact on predictability occurs in data sparse situations. More important than impacting the accuracy of predictions though, these hybrid models provide physical relationships, such as the molecular mass dependence of the critical point or the coefficients within a FH expression. They also afford determination of scaling behavior of theoretical parameters from cloud point experiments instead of more complicated methods. This aspect of physics-incorporated ML models enhances trust in predictions, as well as providing a systematic means to identify anomalous behavior, assess experimental data quality, and reveal unanticipated correlations among factors.

Magnetic resonance imaging (MRI)-active polymers exhibit unique advantages for in vivo diagnosis. Here, in order to endow electrospun fibers with long-term T1 positive MRI visibility, MRI contrast agent (CA), Gd(OH)3, is introduced in a new, extremely convenient method. Crucially, GdCl3 is reacted with NaOH in situ during electrospinning, with flexibility to deliver both well-dispersed and aggregated Gd(OH)3 clusters within a poly(ethylene terephthalate) (PET) matrix. T1 and T2 relaxivities of Gd(OH)3 in PET nanofibers are studied. Well-dispersed Gd(OH)3 (sub-nanometer in size) exhibits 34 times higher T1 relaxivity than aggregated nanoparticles when embedded within the fibers. The morphology, structure, magnetic properties, tensile properties, imaging performance and biosafety of the PET/Gd(OH)3 composite fibers are evaluated to identify the optimum conditions to produce new materials with balanced properties, excellent in vivo positive contrast and approximately 139 days imaging lifetime. Comparing this sample with a commercial CA, only 0.32 wt.% Gd loading is needed to attain similar MRI signal intensity. In summary, PET/Gd(OH)3 long-term MRI-active fibers show great potential for future biomedical applications and the study also provides a promising new general strategy to enhance the MRI T1 positive contrast of electrospun fibers of a whole host of other systems.

Recently, pathway complexity in supramolecular self-assembly has gained great attention due to their ability to control over the dimensions of the nanostructures. Although, the self-assembly of a wide range of organic and π-chromophore-based compounds have been extensively explored in the context of pathway complexity, analogous investigations using peptides have so far received less attention. In this Minireview, we have collated recent examples on control over nano- and secondary structures of self-assembled peptides through pathway dependent approaches. Regulating the competing kinetic vs thermodynamic pathways would aid to create tunable nanostructures with definite size and shape which is very crucial for effective interactions with biological systems and wide variety of applications in biomedicine.

Nanozymes are a class of nanomaterials with enzyme-like catalytic properties, which have environmental tolerance and long-term stability. Improving catalytic activity and expanding the variety of nanozymes are the prerequisites to complement or even replace natural enzymes. The assembly of organic monolayer containing catalytic site on the surface of inorganic nanoparticles is a very effective strategy to improve catalytic activity and expand the variety of nanozymes. Here, we discuss how to construct organic monolayer on the surface of gold nanoparticles, classify the types of organic monolayer, and introduce their applications in nucleic acid hydrolysis and sensing. It is hoped to further promote the research progress of hydrolytic nanozymes.

Rapid detection of unlabeled SARS-CoV-2 genetic target was demonstrated using a competitive displacement hybridization assay made by a nanostructured anodized alumina oxide (AAO) membrane. The assay applied the toehold-mediated strand displacement reaction. The nanoporous surface of the membrane was functionalized with a complementary pair consisting of Cy3-labeled probe and quencher-labeled nucleic acids through a chemical immobilization process. In the presence of the unlabeled SARS-CoV-2 target, the quencher-tagged strand of the immobilized probe-quencher duplex was separated from the Cy3-modifed strand. A stable probe-target duplex formed and regained a strong fluorescence signal, thus enabling real-time and label-free SARS-CoV-2 detection. Assay designs with different numbers of base pair (bp) matches were synthesized to compare their affinities. Because of the large surface of a free-standing nanoporous membrane, two orders enhancement of the fluorescence was observed, where the detection limit of the unlabeled concentration can be improved to 1 nM. The assay was miniaturized by integrating a nanoporous AAO layer onto an optical waveguide device. The detection mechanism and the sensitivity improvement of the AAO-waveguide device were illustrated from the finite difference method (FDM) simulation and the experimental results. Light-analyte interaction was further improved due to the presence of the AAO layer, which created an intermediate refractive index and enhanced the waveguide's evanescent field. Our competitive hybridization sensor is an accurate and label-free testing platform applicable to the deployment of compact and sensitive virus detection strategies.

Nanoparticle (NP) superlattice is a fascinating functional material with periodic long-range ordered structure constructed by self-assembly of inorganic NPs. Due to the coupling effect among the NPs, such superlattice assemblies can exhibit excellent collective properties which are distinct from those of individual NPs. The property of superlattice assemblies not only depends on the property of individual NPs and their packing structures, but also relies on the property of ligands on the NP surface. Among various ligands, the polymeric ligands offer advantages to tune the flexibility of superlattices, the packing structure of NPs, the interparticle distance, as well as the interaction softness. By applying different assembly approaches, one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) superlattices of polymer-grafted NPs (PGNPs) have been successfully obtained. Particularly, the 3D superlattices of PGNPs, which have higher degree of order and better structure symmetry, emerge as promising functional materials with desired mechanical, electronic, optical, and magnetic properties. They can find wide applications in many fields, such as information storage, optoelectronic devices, nanomedicine, and catalysis. This review will summarize the recent progress in the self-assembly of PGNPs into 3D superlattice materials in emulsions and solutions. Special attention is focused on the assembly strategies of 3D superlattice materials and the functions of the superstructures. The precise control over the arrangement structure of NPs and the interparticle interactions by tuning the properties of polymer ligands are highlighted. Finally, we will discuss the challenges and future perspectives of superlattices materials of PGNPs.

Complexation between polymers of different species in a common solvent is a fundamental process in various applications such as functional polymeric membrane and drug delivery, yet the understanding of energetics, phase behaviors, and kinetics of polymer complexation is rather challenging partially due to the multi-component nature of the system. In this work, we investigate the hydrogen-bonding complexation of poly(acrylic acid) (PAA) and poly(vinylpyrrolidone) (PVPON) in different solvents, and identify a variety of phase states, including homogenous solution, solid precipitate, liquid–liquid separation, gelation, and kinetically trapped structures. Among different solvents, N-methyl-2-pyrrolidone (NMP) has a similar structure to the repeating unit of PVPON and the complexation in NMP almost has no heat, suggesting the process is driven by entropy. The PAA/PVPON-NMP system exhibits an upper critical solution temperature; specifically, as the temperature decreases, a homogeneous solution first becomes opalescent, then undergoes a liquid–liquid separation, and finally undergoes a liquid–gel separation. On the other hand, when the polymer concentration is above a threshold, a homogenous solution turns into a gel directly without involving liquid–liquid separation with decreasing temperature. Accordingly, we construct a temperature–concentration phase diagram that shows how the gelation interplays with coacervation. This work provides a broad vision on phase behaviors of polymer complexation.

Conjugated polymers with excellent optoelectronic properties, easy processability, and flexible physical properties are versatile in various applications. In recent years, the precise synthesis of conjugated polymers has attracted much attention due to the close relationship between structure and property. From the perspective of the polymerization mechanism, the synthetic methods of conjugated polymers can be classified into step-growth polymerization, chain-growth polymerization, and iterative synthesis. From step-growth polymerization to iterative synthesis, polymer synthesis becomes more controllable. In this review, we introduce these three synthetic approaches to prepare conjugated polymers with controllable structures based on transition metal-catalyzed cross-coupling reactions and further reveal the control over chemical structures, including length, regioregularity, sequence, and topology. The precise control over the synthesis of conjugated polymer is of great significance for the synthesis of functional polymer with a specific structure, which paves a way for fabricating high-performance devices.

Materials under viscoplastic deformation at ultrahigh strain rates (>106 s−1) often demonstrate anomalous properties due to thermal and stress localization. As a model system, thermoplastic nano-cellular material (NCM) coatings are produced by consolidating microscopic polystyrene shells of nanoscale thin walls using self-limiting electrospray deposition. As both the spatial and temporal characterization scales are crucial, the NCMs are characterized by laser-induced projectile impact test (LIPIT) for understanding their ultrahigh-strain-rate plasticity originating from their porous structures. In LIPIT, supersonic collisions of rigid microspheres create these extreme physical conditions at the microscale. Viscoplastic vertical densification without the Poisson effect is the foremost process in the ultrahigh-rate plastic deformation of the NCM coatings. When the extreme nature of the viscoplastic deformation is promoted by increasing the porosity and reducing the thickness of NCM coatings, significantly more energy dissipation is observed without more material due to the localized feedback between adiabatic plastic deformation and thermal softening. Despite the stochastic and isotropic structural architecture of the NCM, the specific energy absorption of the NCM is high as 170 kJ/kg at the deformation speed of 400 m/s, which is attributed to the nanoscale effects from the thin wall thickness of NCM coatings. The findings suggest the general design rule for enhancing specific energy absorption by creating viscoplastic hot spots under impact loading.

Liquid crystals of disc-like molecules are known for 45 years. 2,3,6,7,10,11-Hexakis(alkyloxy)triphenylene (HATn) containing n = 4 to 11 carbons in its achiral alkyl groups, represents one of the classic families of disc-like molecules. X-ray analysis suggested that disc-like molecules stack on top of each other at irregular spacing in columns distributed in the melt of their alkyl groups forming discotic or columnar or discotic nematic liquid crystals. Interest in discotic liquid crystals comes mostly from their conducting and photoconducting properties. While writing a recent perspective on the 45th anniversary of discotic liquid crystals we realized that the molecular structures of the 3D crystal and 2D liquid crystal phases of discotic molecules were never determined at the molecular level, in spite of the great interest in their physical properties. Since structure determines function, we decided to perform a detailed investigation of the molecular structure of HATn self-organizations by reconstructing their oriented fiber X-ray diffractograms both in the crystal and liquid crystal states. This communication reports the synthesis, analysis by differential scanning calorimetry of HATn containing n = 4 to 12 carbons in its achiral alkyl groups and the molecular structure of HAT4 in its crystal and liquid crystal states. Unexpectedly, a highly ordered 8/1 helical pyramidal crystalline column assembled from a crown-like conformation of the HAT4 and a non-helical column of the discotic liquid crystal state, the last similar to the original suggested supramolecular structure, were resolved for the first time at the molecular level. These preliminary results raise a lot of fundamental issues in the area of discotic and columnar self-organizations and of related helical columnar self-organizations generated with different building blocks and belonging to different disciplines. A comprehensive mechanistic elucidation of the molecular details of helical and non-helical self-organizations in synthetic complex systems may become as influential in the field of soft condensed matter as that of helical and non-helical self-organizations in the field of molecular biology.

Thermosets and their composites have occupied a key place in the polymeric material industry for both plastics and rubbers. Carbon material/thermoset composite is a major category thereof. The addition of carbon material (such as carbon fibers, carbon nanotubes (CNTs), and graphene) endows polymeric materials with better mechanical properties, enhanced optical and electrical properties, etc. However, due to the thermoset nature, the covalently crosslinked network brings huge reprocessing and recycling difficulties. The development of vitrimers paves a new way to produce recyclable and degradable thermosets. A series of carbon material/vitrimer composites have also been innovated, aiming at sustainable high-performance materials with better physical properties, recyclability, reprocessablity, and other novel stimuli-responsive functions. This review summarized the progress of carbon material/vitrimer composites in the past decade. A general introduction of vitrimer and the preparation strategies of different kinds of carbon material/vitrimer composites are given at first. Because of the vitrimeric nature, the service life of those composites could be significantly prolonged by reprocessing, healing, and recycling, the related strategies of which are described and summarized in detail. Then, the improved properties and new functions enabled by the incorporation of fillers are also overviewed. Our outlook on the future directions of carbon material/vitrimer composites is present at the end.