Branching out: Thiol–yne chemistry is emerging as new tool for polymer chemists, as it represents a unique and efficient coupling procedure to create highly branched structures (see scheme). This ...method can be used to prepare highly functional dendrimers and hyperbranched polymers.
Cyclic versus linear: The superiority of cyclic polymers over their linear counterparts is highlighted. Cyclic poly(2‐oxazoline)s have been shown to provide excellent shielding properties when ...grafted to TiO2 surfaces and Fe3O4 nanoparticles owing to their ultrahigh grafting densities leading to low friction surfaces, superior antifouling properties, and extreme nanoparticle stabilization.
Poly(ethylene glycol) (PEG) is the most used polymer and also the gold standard for stealth polymers in the emerging field of polymer-based drug delivery. The properties that account for the ...overwhelming use of PEG in biomedical applications are outlined in this Review. The first approved PEGylated products have already been on the market for 20 years. A vast amount of clinical experience has since been gained with this polymer--not only benefits, but possible side effects and complications have also been found. The areas that might need consideration and more intensive and careful examination can be divided into the following categories: hypersensitivity, unexpected changes in pharmacokinetic behavior, toxic side products, and an antagonism arising from the easy degradation of the polymer under mechanical stress as a result of its ether structure and its non-biodegradability, as well as the resulting possible accumulation in the body. These possible side effects will be discussed in this Review and alternative polymers will be evaluated.
Despite the fact that pillarnarenes receive major interest as building blocks for supramolecular chemistry and advanced materials, their functionalization is generally limited to the modification of ...the hydroxy or alkoxy units present on the rims. This limited structural freedom restricts further developments and has very recently been overcome. In this article, we highlight three very recent studies demonstrating further structural diversification of pillarnarenes by partial removal of the alkoxy substituents on the rims, which can be considered as the next generation of pillarnarenes.
The next generation: Recent developments made in the field of pillarnarene‐based macrocyclic molecules to go beyond single macrocyclic structures with two alkoxy substituents on every benzene ring are highlighted. The recently introduced tiaranarenes, leaning pillarnarenes, and BowtieArenes with incomplete alkoxy substitution may be regarded as a next step in the structural diversification of pillarnarenes.
Photoswitches: Exciting recent progress realized in the field of light‐controlled polymeric materials is highlighted. It is discussed how the rational choice of azobenzene molecules and their ...incorporation into complex materials by making use of physical interactions can lead to genuine photocontrollable polymeric systems.
The living cationic ring-opening polymerization of 2-oxazolines has been studied in great detail since its discovery in 1966. The versatility of this living polymerization method allows ...copolymerization of a variety of 2-oxazoline monomers to give a range of tunable polymer properties that enable, for example, hydrophilic, hydrophobic, fluorophilic, as well as hard and soft materials to be obtained. However, this class of polymers was almost forgotten in the 1980s and 1990s because of their long reaction times and limited application possibilities. In the new millennium, a revival of poly(2-oxazoline)s has arisen because of their potential use as biomaterials and thermoresponsive materials, as well as the easy access to defined amphiphilic structures for (hierarchical) self-assembly. Recent developments that illustrate the potential of poly(2-oxazoline)s are discussed in this Review. In addition, the promising combination of poly(2-oxazoline)s and click chemistry is illustrated.
Boronic acid-containing (co)polymers have fascinated researchers for decades, garnering attention for their unique responsiveness toward 1,2- and 1,3-diols, including saccharides and nucleotides. The ...applications of materials that exert this property are manifold including sensing, but also self-regulated drug delivery systems through responsive membranes or micelles. In this review, some of the main applications of boronic acid containing (co)polymers are discussed focusing on the role of the boronic acid group in the response mechanism. We hope that this summary, which highlights the importance and potential of boronic acid-decorated polymeric materials, will inspire further research within this interesting field of responsive polymers and polymeric materials.
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•Discussion of emerging trends for the synthesis of poly(2-oxazoline)s.•Discussion of emerging trends for applications of poly(2-oxazoline)s.•Discussion of future vision on ...poly(2-oxazoline)s.
Poly(2-oxazoline)s have gained significant interest in the past decade, especially driven by their high potential for biomedical applications, amongst others to substitute poly(ethylene glycol). Within this perspective article the emerging trends in the area of poly(2-oxazoline)s are discussed with a focus on synthetic advances, including the development of high molar mass polymers, the broadening of the cyclic imino ether monomer range, and the development of degradable poly(2-oxazoline) derivatives. Furthermore, emerging trends in the use of poly(2-oxazoline)s will be highlighted, including their use to study basic fundamental polymer properties, specific biomedical applications, including drug delivery and 3D scaffolds, as well as other applications as interlayers in organic devices and polymer gel electrolytes. Finally, this perspective article provides a discussion on the future vision for the area of poly(2-oxazoline)s.
No copper needed: In recent years, a large number of metal-free click reactions have been reported based on thiol-ene radical additions, Diels-Alder reactions, and Michael additions. In this ...Minireview, special attention is given to the advantages and limitations of the different methods to evaluate whether they have the potential to surpass the overwhelming success of the copper(I)-catalyzed azide-alkyne cycloaddition.The overwhelming success of click chemistry encouraged researchers to develop alternative "spring-loaded" chemical reactions for use in different fields of chemistry. Initially, the copper(I)-catalyzed azide-alkyne cycloaddition was the only click reaction. In recent years, metal-free 3+2 cycloaddition reactions, Diels-Alder reactions, and thiol-alkene radical addition reactions have come to the fore as click reactions because of their simple synthetic procedures and high yields. Furthermore, these metal-free reactions have wide applicability and are physiologically compatible. These and other alternative click reactions expand the opportunities for synthesizing small organic compounds as well as tailor-made macromolecules and bioconjugates. This Minireview discusses the success and applicability of new, in particular metal-free, click reactions.
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The mechanism of polycation cytotoxicity and the relationship to polymer molecular weight is poorly understood. To gain an insight into this important phenomenon a range of newly ...synthesised uniform (near monodisperse) linear polyethylenimines, commercially available poly(l-lysine)s and two commonly used PEI-based transfectants (broad 22kDa linear and 25kDa branched) were tested for their cytotoxicity against the A549 human lung carcinoma cell line. Cell membrane damage assays (LDH release) and cell viability assays (MTT) showed a strong relationship to dose and polymer molecular weight, and increasing incubation times revealed that even supposedly “non-toxic” low molecular weight polymers still damage cell membranes. The newly proposed mechanism of cell membrane damage is acid catalysed hydrolysis of lipidic phosphoester bonds, which was supported by observations of the hydrolysis of DOPC liposomes.
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