Supramolecular Diblock Copolymers Featuring Well‐defined Telechelic Building Blocks

We report supramolecular AB diblock copolymers comprised of well‐defined telechelic building blocks. Helical motifs, formed via reversible addition‐fragmentation chain‐transfer (RAFT) or anionic polymerization, are assembled with coil‐forming and sheet‐featuring blocks obtained via atom‐transfer radical polymerization (ATRP) or ring‐opening metathesis polymerization (ROMP). Interpolymer hydrogen bonding or metal‐coordination achieves dynamic diblock architectures featuring hybrid topologies of coils, helices, and/or π‐stacked sheets that, on a basic level, mimic protein structural motifs in fully synthetic systems. The intrinsic properties of each block (e.g., circular dichroism and fluorescence) remain unaffected in the wake of self‐assembly. This strategy to develop complex synthetic polymer scaffolds from functional building blocks is significant in a field striving to produce architectures reminiscent of biosynthesis, yet fully synthetic in nature. This is the first plug‐and‐play approach to fabricate hybrid π‐sheet/helix, π‐sheet/coil, and helix/coil architectures via directional self‐assembly.     

Biofunctionalized Electrospun PCL‐PIBMD/SF Vascular Grafts with PEG and Cell‐Adhesive Peptides for Endothelialization

Artificial small‐caliber vascular grafts are still limited in clinical application because of thrombosis, restenosis, and occlusion. Herein, a small‐caliber vascular graft (diameter 2 mm) is fabricated from poly(ε‐caprolactone)‐b‐poly(isobutyl‐morpholine‐2,5‐dione) (PCL‐PIBMD) and silk fibroin (SF) by electrospinning technology and then biofunctionalized with low‐fouling poly(ethylene glycol) (PEG) and two cell‐adhesive peptide sequences (CREDVW and CAGW) with the purpose of enhancing antithrombogenic activity and endothelialization. The successful grafting of PEG and peptide sequences is confirmed by X‐ray photoelectron spectroscopy. The suitable surface wettability of the modified vascular graft is testified by water contact angle analysis. The surface hemocompatibility is verified by platelet adhesion assays and protein adsorption assays, and the results demonstrate that both platelet adhesion and protein adsorption on the biofunctionalized surface are significantly reduced. In vitro studies demonstrate that the biofunctionalized surface with suitable hydrophilicity and cell‐adhesive peptides can selectively promote the adhesion, spreading, and proliferation of human umbilical vein endothelial cells. More importantly, compared with control groups, this biofunctionalized small‐caliber vascular graft shows high long‐term patency and endothelialization after 10 weeks of implantation. The biofunctionalization with PEG and two cell‐adhesive peptide sequences is an effective method to improve the endothelialization and long‐term performance of synthetic vascular grafts.     

The Assembly of Supramolecular Boxes and Coordination Polymers Based on Bis‐Zinc‐Salphen Building Blocks

We report the assembly of supramolecular boxes and coordination polymers based on a rigid bis‐zinc(II)‐salphen complex and various ditopic nitrogen ligands. The use of the bis‐zinc(II)‐salphen building block in combination with small ditopic nitrogen ligands gave organic coordination polymers both in solution as well as in the solid state. Molecular modeling shows that supramolecular boxes with small internal cavities can be formed. However, the inability to accommodate solvent molecules (such as toluene) in these cavities explains why coordination polymers are prevailing over well‐defined boxes, as it would lead to an energetically unfavorable vacuum. In contrast, for relatively longer ditopic nitrogen ligands, we observed the selective formation of supramolecular box assemblies in all cases studied. The approach can be easily extended to chiral analogues by using chiral ditopic nitrogen ligands.     

Development of Poor Cell Adhesive Immersion Precipitation Membranes Based on Supramolecular Bis‐Urea Polymers

A variety of biomedical applications requires tailored membranes; fabrication through a mix‐and‐match approach is simple and desired. Polymers based on supramolecular bis‐urea (BU) moieties are capable of modular integration through directed non‐covalent stacking. Here, it is proposed that non‐cell adhesive properties can be introduced in polycaprolactone‐BU‐based membranes by the addition of poly(ethylene glycol) (PEG)‐BU during immersion precipitation membrane fabrication, while unmodified PEG is not retained in the membrane. PEG‐BU addition results in denser membranes with a similar pore size compared to pristine membranes, while PEG addition induces defect formation. Infrared spectroscopy and surface hydrophobicity measurements indicate that PEG‐BU is retained during membrane processing. Additionally, PEG‐BU incorporation successfully leads to poor cell adhesive surfaces. No evidence is observed to indicate PEG retention. The results obtained indicate that the BU system enables intimate mixing of BU‐modified polymers after processing. Collectively, the results provide the first steps toward BU‐based immersion precipitated supramolecular membranes for biomedical applications.     

Non‐Newtonian Polymer–Nanoparticle Hydrogels Enhance Cell Viability during Injection

Drug delivery and cell transplantation require minimally invasive deployment strategies such as injection through clinically relevant high‐gauge needles. Supramolecular hydrogels comprising dodecyl‐modified hydroxypropylmethylcellulose and poly(ethylene glycol)‐block‐poly(lactic acid) have been previously demonstrated for the delivery of drugs and proteins. Here, it is demonstrated that the rheological properties of these hydrogels allow for facile injectability, an increase of cell viability after injection when compared to cell viabilities of cells injected in phosphate‐buffered saline, and homogeneous cell suspensions that do not settle. These hydrogels are injected at 1 mL min^?1 with pressures less than 400 kPa, despite the solid‐like properties of the gel when at rest. The cell viabilities immediately after injection are greater than 86% for adult human dermal fibroblasts, human umbilical vein cells, smooth muscle cells, and human mesenchymal stem cells. Cells are shown to remain suspended and proliferate in the hydrogel at the same rate as observed in cell media. The work expands on the versatility of these hydrogels and lays a foundation for the codelivery of drugs, proteins, and cells.     

A Novel and Non‐Cytotoxic Self‐Healing Supramolecular Elastomer Synthesized with Small Molecular Biological Acids

A novel and non‐cytotoxic self‐healing supramolecular elastomer (SE) is synthesized with small‐molecular biological acids by hydrogen‐bonding interactions. The synthesized SEs behave as rubber at room temperature without additional plasticizers or crosslinkers, which is attributed to the phase‐separated structure. The SE material exhibits outstanding self‐healing capability at room temperature and essential non‐cytotoxicity, which makes it a potential candidate for biomedical applications.

     

Inversion of Supramolecular Helicity in Oligo‐p‐phenylene‐Based Supramolecular Polymers: Influence of Molecular Atropisomerism

The helical organization of oligo‐p‐phenylene‐based organogelators has been investigated by atomic force microscopy, circular and vibrational circular dichroism, and Raman techniques. Whilst OPPs with more than two phenyl rings in the core self‐assemble into left‐handed helices, that with a biphenyl core shows an inversion of the supramolecular helicity depending on the formation conditions through the atropisomerism of the biphenyl central unit. The results presented herein outline a new example of kinetically controlled modulation of supramolecular helicity.     

cyclo‐P4 Building Blocks: Achieving Non‐Classical Fullerene Topology and Beyond

The cyclo‐P₄ complexes [Cp^RTa(CO)₂(η⁴‐P₄)] (Cp^R: Cp′′=1,3‐C₅H₃tBu₂, Cp′′′=1,2,4‐C₅H₂tBu₃) turned out to be predestined for the formation of hollow spherical supramolecules with non‐classical fullerene‐like topology. The resulting assemblies constructed with CuX (X=Cl, Br) showed a highly symmetric 32‐vertex core of solely four‐ and six‐membered rings. In some supramolecules, the inner cavity was occupied by an additional CuX unit. On the other hand, using CuI, two different supramolecules with either peanut‐ or pear‐like shapes and outer diameters in the range of 2–2.5 nm were isolated. Furthermore, the spherical supramolecules containing Cp′′′ ligands at tantalum are soluble in CH₂Cl₂. NMR spectroscopic investigations in solution revealed the formation of isomeric supramolecules owing to the steric hindrance caused by the third tBu group on the Cp′′′ ligand. In addition, a 2D coordination polymer was obtained and structurally characterized.     

Self‐Healing Supramolecular Hydrogels for Tissue Engineering Applications

Self‐healing supramolecular hydrogels have emerged as a novel class of biomaterials that combine hydrogels with supramolecular chemistry to develop highly functional biomaterials with advantages including native tissue mimicry, biocompatibility, and injectability. These properties are endowed by the reversibly cross‐linked polymer network of the hydrogel. These hydrogels have great potential for realizing yet to be clinically translated tissue engineering therapies. This review presents methods of self‐healing supramolecular hydrogel formation and their uses in tissue engineering as well as future perspectives.     

Non‐Centrosymmetric Homochiral Supramolecular Polymers of Tetrahedral Subphthalocyanine Molecules

A combination of spectroscopy (UV/Vis absorption, emission, and circular dichroism), microscopy (AFM and TEM), and computational studies reveal the formation of non‐centrosymmetric homochiral columnar subphthalocyanine assemblies. These assemblies form through a cooperative supramolecular polymerization process driven by hydrogen‐bonding between amide groups, π–π stacking, and dipolar interactions between axial B? F bonds.     

Supramolecular Nested Microbeads as Building Blocks for Macroscopic Self‐Healing Scaffolds

The ability to construct self‐healing scaffolds that are injectable and capable of forming a designed morphology offers the possibility to engineer sustainable materials. Herein, we introduce supramolecular nested microbeads that can be used as building blocks to construct macroscopic self‐healing scaffolds. The core–shell microbeads remain in an “inert” state owing to the isolation of a pair of complementary polymers in a form that can be stored as an aqueous suspension. An annealing process after injection effectively induces the re‐construction of the microbead units, leading to supramolecular gelation in a preconfigured shape. The resulting macroscopic scaffold is dynamically stable, displaying self‐recovery in a self‐healing electronic conductor. This strategy of using the supramolecular assembled nested microbeads as building blocks represents an alternative to injectable hydrogel systems, and shows promise in the field of structural biomaterials and flexible electronics.     

Anchoring Supramolecular Polymers to Human Red Blood Cells by Combining Dynamic Covalent and Non‐Covalent Chemistries

Understanding cell/material interactions is essential to design functional cell‐responsive materials. While the scientific literature abounds with formulations of biomimetic materials, only a fraction of them focused on mechanisms of the molecular interactions between cells and material. To provide new knowledge on the strategies for materials/cell recognition and binding, supramolecular benzene‐1,3,5‐tricarboxamide copolymers bearing benzoxaborole moieties are anchored on the surface of human erythrocytes via benzoxaborole/sialic‐acid binding. This interaction based on both dynamic covalent and non‐covalent chemistries is visualized in real time by means of total internal reflection fluorescence microscopy. Exploiting this imaging method, we observe that the functional copolymers specifically interact with the cell surface. An optimal fiber affinity towards the cells as a function of benzoxaborole concentration demonstrates the crucial role of multivalency in these cell/material interactions.     

Three‐Layered PCL Grafts Promoted Vascular Regeneration in a Rabbit Carotid Artery Model

In this study, a three layered poly (ε‐caprolactone) (PCL) graft (tPCL) was fabricated by electrospinning PCL and electrospraying poly (ethylene oxide) (PEO), which has a thin dense inner layer, a loose middle layer, and a dense outer layer. Regular PCL grafts (rPCL) with only a dense layer were used as control. In vivo evaluation was performed in rabbit carotid artery. Enhanced cell infiltration, rapid regeneration of endothelium and smooth muscle layers, and increased elastin deposition were observed within the tPCL graft wall. After 3 months, tPCL grafts showed faster PCL degradation than the rPCL grafts. Infiltrated macrophages in the tPCL grafts secreted higher level of monocyte chemoattractant protein‐1 (MCP‐1) and vascular endothelial growth factor (VEGF) which enhanced vascular regeneration. In conclusion, the tPCL graft may be a useful vascular prosthesis and worth for further investigation.

     

Carboxylate‐Driven Supramolecular Assemblies of Protonated meso‐Aryl‐Substituted Dipyrrolylpyrazoles

Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4‐position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single‐crystal X‐ray and synchrotron XRD analyses. In particular, the complexation of protonated dpp species possessing long alkyl chains with dicarboxylates resulted in highly ordered assembled structures, the packing modes of which as lamellar structures were controlled by the lengths of the spacer units between two carboxylate moieties. The charge‐carrier transporting properties of the solid materials were also controlled by bound anions, including dicarboxylates.     

Coordination‐Driven Self‐Assembly of PEO‐Functionalized Perylene Bisimides: Supramolecular Diversity from a Limited Set of Molecular Building Blocks

A limited number of poly(ethylene oxide)‐substituted perylene bisimides, some of which are equipped with terpyridine ligands for transition‐metal coordination (see structure), combine different types of noncovalent interactions to yield optoelectronically active organic materials with different types of supramolecular morphologies.

     

Self‐Stabilized and Strongly Adhesive Supramolecular Polymer Protective Layer Enables Ultrahigh‐Rate and Large‐Capacity Lithium‐Metal Anode

Constructing a solid electrolyte interface (SEI) is a highly effective approach to overcome the poor reversibility of lithium (Li) metal anodes. Herein, an adhesive and self‐healable supramolecular copolymer, comprising of pendant poly(ethylene oxide) (PEO) segments and ureido‐pyrimidinone (UPy) quadruple‐hydrogen‐bonding moieties, is developed as a protection layer of Li anode by a simple drop‐coating. The protection performance of in‐situ‐formed LiPEO–UPy SEI layer is significantly enhanced owing to the strong binding and improved stability arising from a spontaneous reaction between UPy groups and Li metal. An ultrathin (approximately 70 nm) LiPEO–UPy layer can contribute to stable and dendrite‐free cycling at a high areal capacity of 10 mAh cm^?2 at 5 mA cm^?2 for 1000 h. This coating together with the promising electrochemical performance offers a new strategy for the development of dendrite‐free metal anodes.     

Photoreversible Supramolecular Polymerisation and Hierarchical Organization of Hydrogen‐Bonded Supramolecular Co‐polymers Composed of Diarylethenes and Oligothiophenes

Diarylethene 1 equipped with two monotopic melamine hydrogen‐bonding sites and oligothiophene‐functionalized ditopic cyanurate (OTCA) were mixed in a nonpolar solvent to form AA‐BB‐type supramolecular co‐polymers (SCPs) bearing photoswitchable moieties in their main chains and extended π systems as side chains. UV/Vis, fluorescence, dynamic light scattering (DLS), TEM, and AFM studies revealed that the two functional co‐monomers formed flexible quasi‐one‐dimensional SCPs in solution that hierarchically self‐organized into helical nanofibers through H‐aggregation of the oligothiophene side chains. Upon irradiating the SCPs with UV light, a transition occurred from the H‐aggregated state to non‐aggregated monomeric oligothiophene side chains, as shown by spectroscopic studies, which indicates the formation of small oligomeric species held together only by hydrogen‐bonding interactions. TEM and AFM visualized unfolded fibrils corresponding to elongated single SCP chains formed upon removal of solvent. The helical nanofibers were regenerated upon irradiating the UVirradiated solution with visible light. These results demonstrated that the supramolecular polymerisation followed by hierarchical organization can be effectively controlled by proper supramolecular designs using diarylethenes and π‐conjugated oligomers.     

Non‐Covalent Interactions in Supramolecular Assemblies Investigated with Electron Spectroscopies

A new view: A picture of the different non‐covalent interactions relevant for the self‐assembly of organic layers and their spectroscopic fingerprints is provided (see figure). In particular, state‐of‐the‐art spectroscopic measurements are performed for supramolecular assemblies, comparing the electronic structure of single‐component layers with that of binary organic layers.

     

Fabrication of Supramolecular Semiconductor Block Copolymers by Ring‐Opening Metathesis Polymerization

ω‐Telechelic poly(p‐phenylene vinylene) species (PPVs) are prepared by living ring‐opening metathesis polymerization of a [2.2]paracyclophane‐1,9‐diene in the presence of Hoveyda–Grubbs 2nd generation initiator, with terminating agents based on N¹,N³‐bis(6‐butyramidopyridin‐2‐yl)‐5‐hydroxyisophthalamide (Hamilton wedge), cyanuric acid, Pd^II–SCS‐pincer, or pyridine moieties installing the supramolecular motifs. The resultant telechelic polymers are self‐assembled into supramolecular block copolymers (BCPs) via metal coordination or hydrogen bonding and analyzed by ¹H NMR spectroscopy. The optical properties are examined, whereby individual PPVs exhibit similar properties regardless of the nature of the end group. Upon self‐assembly, different behaviors emerge: the hydrogen‐bonding BCP behaves similarly to the parent PPVs whereas the metallosupramolecular BCP demonstrates a hypsochromic shift and a more intense emission owing to the suppression of aggregation. These results demonstrate that directional self‐assembly can be a facile method to construct BCPs with semiconducting networks, while combating solubility and aggregation.