Supramolecular Linear-g-Hyperbranched Graft Polymers: Topology and Binding Strength of Hyperbranched Side Chains

Surface Functionality-Regulated and Entropy-Driven Thermodynamics of the Formation of Coordination Nanocages

Coordination nanocages (CNCs) are under intense research in nanoscience and supramolecular chemistry for their enriched surface functionalities and micro-porosity; however, the understanding of their formation mechanism is still poor due to the difficulty in probing their solution structures. Herein, the CNC formation process from the coordination complexation of the macromolecular isophthalic acid (IPA) ligand and Cu²⁺ is studied via isothermal titration calorimetry, and its entropy-driven feature is revealed to be originated from the collapse of solvation layers of the assembly units. The CNC formation is thermodynamically less favored with smaller binding constants when the sizes of macromolecular IPA ligands are larger, which originated from the space crowding of macromolecules of the ligands on CNC surfaces and the resulting entropy loss of polymer chain conformations. Meanwhile, the chemical equilibrium of CNC formation can be tuned upon altering the Cu²⁺/IPA ratio, and the yield of CNCs, suggested from size exclusion chromatography studies, decreases when excessive Cu²⁺ is applied, providing guidelines for CNC design and synthesis.

Conducting Polymer Grafting: Recent and Key Developments

Since the discovery of conductive polyacetylene, conductive electroactive polymers are at the focal point of technology generation and biocommunication materials. The reasons why this research never stops growing, are twofold: first, the demands from the advanced technology towards more sophistication, precision, durability, processability and cost-effectiveness; and second, the shaping of conducting polymer research in accordance with the above demand. One of the major challenges in conducting polymer research is addressing the processability issue without sacrificing the electroactive properties. Therefore, new synthetic designs and use of post-modification techniques become crucial than ever. This quest is not only advancing the field but also giving birth of new hybrid materials integrating merits of multiple functional motifs. The present review article is an attempt to discuss the recent progress in conducting polymer grafting, which is not entirely new, but relatively lesser developed area for this class of polymers to fine-tune their physicochemical properties. Apart from conventional covalent grafting techniques, non-covalent approach, which is relatively new but has worth creation potential, will also be discussed. The aim is to bring together novel molecular designs and strategies to stimulate the existing conducting polymer synthesis methodologies in order to enrich its fascinating chemistry dedicated toward real-life applications.

Engineering the morphology of hydrogen-bonded comb-shaped supramolecular polymers: from solution self-assembly to confined assembly

A library of nanostructures and multi-stage morphology transformation are realized by introducing a 3D confined assembly to hydrogen-bonded comb-shaped supramolecular polymer architectures.

Cucurbit[8]uril-Based Water-Soluble Supramolecular Dendronized Polymer: Evidence from Single Polymer Chain Morphology and Force Spectroscopy

A novel water-soluble supramolecular dendronized polymer (SDP) was prepared through cucurbit[8]uril (CB[8])-naphthalene host-guest interaction. The composition ratio between BDP and CB[8] of as-prepared luminescent supramolecular polymer was confirmed by ¹H NMR technique and mass spectrometry. In addition, atomic force microscopy (AFM) images showing the polymer chain length up to 150 nm and height up to 1.75 nm unambiguously demonstrate the supramolecular polymer formation. This work might be useful for designing other main chain supramolecular dendronized polymers.

Supramolecular Graft Copolymerization of a Polyester by Guest-Selective Encapsulation of a Self-Assembled Capsule

Repeating guest units of polyesters poly-(R)-2 were selectively encapsulated by capsule 1(BF₄ )₄ to produce supramolecular graft polymers. The encapsulation of the guest units was confirmed by ¹ H NMR spectroscopy. The graft polymer structures were confirmed by the increase in the hydrodynamic radii and the solution viscosities of the polyesters upon complexation of the capsule. After the capsule was formed, atomic force microscopy showed extension of the polyester chains. The introduction of the graft chains onto poly-(R)-2 resulted in the main chain of the polymer having an M-helical morphology. The complexation of copolymers poly-[(R)-2-co-(S)-2] by the capsule gave rise to the unique chiral amplification known as the majority-rules effect.

Supramolecular hyperbranched polymers

This feature article presents a systematic summary of the synthesis strategies including direct and indirect approaches for obtaining supramolecular hyperbranched polymers (SHPs).

Morphological Evolution of Self-Assembled Structures Induced by the Molecular Architecture of Supra-Amphiphiles

A series of telechelic supramolecular amphiphiles [POSS-Azo₈@(β-CD-PDMAEMA)_1→8] was accomplished by orthogonally coupling the multiarm host polymer β-cyclodextrin-poly(dimethylaminoethyl methacrylate) (β-CD-PDMAEMA) with an octatelechelic guest molecule azobenzene modified-polyhedral oligomeric silsesquioxanes (POSS-Azo₈) under different host-guest ratios. These telechelic supramolecular amphiphiles possess a rigid core and flexible corona. Increasing the multiarm host polymer coupled onto the rigid POSS core made the molecular architecture tend to be symmetrical and spherical. POSS-Azo₈@[β-CD-PDMAEMA]_1→8 could self-assemble into diverse morphologies evolving from spherical micelles, wormlike micelles, and branched aggregates to bowl-shaped vesicles. Distinct from the traditional linear amphiphilic polymers, we discovered that the self-assembly of POSS-Azo₈@[β-CD-PDMAEMA]_1→8 was dominantly regulated by their molecular architectures instead of hydrophilicity, which has also been verified using computer simulation results.

Applications of isothermal titration calorimetry - the research and technical developments from 2011 to 2015

Isothermal titration calorimetry is a widely used biophysical technique for studying the formation or dissociation of molecular complexes. Over the last 5 years, much work has been published on the interpretation of isothermal titration calorimetry (ITC) data for single binding and multiple binding sites. As over 80% of ITC papers are on macromolecules of biological origin, this interpretation is challenging. Some researchers have attempted to link the thermodynamics constants to events at the molecular level. This review highlights work carried out using binding sites characterized using x-ray crystallography techniques that allow speculation about individual bond formation and the displacement of individual water molecules during ligand binding and link these events to the thermodynamic constants for binding. The review also considers research conducted with synthetic binding partners where specific binding events like anion-π and π-π interactions were studied. The revival of assays that enable both thermodynamic and kinetic information to be collected from ITC data is highlighted. Lastly, published criticism of ITC research from a physical chemistry perspective is appraised and practical advice provided for researchers unfamiliar with thermodynamics and its interpretation. Copyright © 2016 John Wiley & Sons, Ltd.

A straightforward approach for one-pot synthesis of noncovalently connected graft copolymers with unique self-assembly nanostructures

Noncovalently connected polymers were prepared by one-pot efficient host–guest complexation between β-CD and adamantane moieties followed by acyclic diene metathesis polymerization or carried out simultaneously, and further self-assembled into supramolecular nanostructures with diverse morphologies.

Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation

The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

Temperature sensitive supramolecular self assembly of per-6-PEO-β-cyclodextrin and α,ω-di-(adamantylethyl)poly(N-isopropylacrylamide) in water

The host/guest interactions in water of a star polymer consisting of a β-cyclodextrin (β-CD) core bearing six poly(ethylene oxide) arms linked to the C6 positions of β-CD (β-CD-PEO7, Mn 5000 g mol(-1)) and α,ω-di-(adamantylethyl)poly(N-isopropylacrylamide) (Ad-PNIPAM-12K, Mn 12,000 g mol(-1)) were studied by 1D and 2D (1)H and (13)C NMR spectroscopy, isothermal calorimetry (ITC), and light scattering (LS). In cold water (T < 26 °C) supramolecular "dumbbell" assemblies, consisting of PNIPAM chains with β-CD/Ad inclusion complexes at each end, formed viaβ-CD-insertion of the terminal Ads through the β-CD secondary face. Light scattering, microcalorimetry (DSC), and DOSY NMR studies indicated that mixed aqueous solutions of β-CD-PEO7 and Ad-PNIPAM-12K undergo a reversible heat-induced phase transition at ∼32 °C, accompanied by a release of a fraction of the Ad-bound β-CD-PEO7 into bulk solution and the formation of aggregated Ad-PNIPAM-12K stabilized by a β-CD-PEO7 shell.

Aliphatic Polyethers: Classical Polymers for the 21st Century

Polyethers-polymers with the structural element (R'-O-R)n in their backbone--are an old class of polymers which were already used at the time of the ancient Egyptians. However, still today these materials are highly important with applications in all areas of our life, reaching from the automotive and paper industry to cosmetics and biomedical applications. In this Review, different aliphatic polyethers like poly(epoxide)s, poly(oxetane)s, and poly(tetrahydrofuran) are discussed. Special emphasis is placed on the history, the polymerization techniques (industrially and in academia), the properties, the applications as well as recent developments of these materials.

A pH-responsive amphiphilic supramolecular graft copolymer constructed by crown ether based molecular recognition

Based on the bis(m-phenylene)-32-crown-10/paraquat molecular recognition motif in water, we have successfully prepared an amphiphilic supramolecular graft copolymer by the combination of modified hydrophilic poly(ethylene oxide) and hydrophobic polystyrene. It could self-assemble into pH-responsive bilayer vesicles in water.

Novel amino-cyclodextrin cross-linked oligomer as efficient carrier for anionic drugs: a spectroscopic and nanocalorimetric investigation

The amino groups of a novel oligomer of amino-cyclodextrins play a relevant role in the recognition process of diclofenac and this highlights the potential of short polymeric chains as new drug carriers.

Hyperbranched polymers: advances from synthesis to applications

This review summarizes the advances in hyperbranched polymers from the viewpoint of structure, click synthesis and functionalization towards their applications in the last decade.

Self-assembly behavior of a linear-star supramolecular amphiphile based on host-guest complexation

A star polymer, β-cyclodextrin-poly(l-lactide) (β-CD-PLLA), and a linear polymer, azobenzene-poly(ethylene glycol) (Azo-PEG), could self-assemble into a supramolecular amphiphilic copolymer (β-CD-PLLA@Azo-PEG) based on the host-guest interaction between β-CD and azobenzene moieties. This linear-star supramolecular amphiphilic copolymer further self-assembled into a variety of morphologies, including sphere-like micelle, carambola-like micelle, naan-like micelle, shuttle-like lamellae, tube-like fiber, and random curled-up lamellae, by tuning the length of hydrophilic or hydrophobic chains. The variation of morphology was closely related to the topological structure and block ratio of the supramolecular amphiphiles. These self-assembly structures could disassemble upon an ultraviolet (UV) light irradiation.

Recent advances in glycerol polymers: chemistry and biomedical applications

Glycerol polymers are attracting increased attention due to the diversity of polymer compositions and architectures available. This article provides a brief chronological review on the current status of these polymers along with representative examples of their use for biomedical applications. First, the underlying chemistry of glycerol that provides access to a range of monomers for subsequent polymerizations is described. Then, the various synthetic methodologies to prepare glycerol-based polymers including polyethers, polycarbonates, polyesters, and so forth are reviewed. Next, several biomedical applications where glycerol polymers are being investigated including carriers for drug delivery, sealants or coatings for tissue repair, and agents possessing antibacterial activity are described. Fourth, the growing market opportunity for the use of polymers in medicine is described. Finally, the findings are concluded and summarized, as well as the potential opportunities for continued research efforts are discussed.

Inclusion and functionalization of polymers with cyclodextrins: current applications and future prospects

The numerous hydroxyl groups available in cyclodextrins are active sites that can form different types of linkages. They can be crosslinked with one another, or they can be derivatized to produce monomers that can form linear or branched networks. Moreover, they can form inclusion complexes with polymers and different substrates, modifying their physicochemical properties. This review shows the different applications using polymers with cyclodextrins, either by forming inclusion complexes, ternary complexes, networks, or molecularly imprinted polymers (MIPs). On one hand, the use of cyclodextrins enhances the properties of each polymer, and on the other the use of polymers decreases the amount of cyclodextrins required in different formulations. Both cyclodextrins and polymers contribute synergistically in several applications such as pharmacological, nutritional, environmental, and other industrial fields. The use of polymers based on cyclodextrins is a low cost easy to use potential tool with great future prospects.

Dendronized supramolecular polymers

Supramolecular polymers from dendritic motifs combine the dynamic nature of supramolecular construction and inherent features from covalent dendronized polymers.

Synthesis and encapsulation of an amphiphilic thermoresponsive star polymer with β-cyclodextrin and hyperbranched poly(oligo(ethylene glycol)methacrylate) as building blocks

Schematic illustrations of the thermally-induced self-assembly and possible encapsulation behaviors with single or multi-guests for PE-CD–POEGMAS.