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A 'Switch' catalysis method is reviewed whereby a single catalyst is switched between ring-opening polymerization and ring-opening copolymerization cycles. It allows the efficient synthesis of block copolymers from mixtures of lactones, epoxides, anhydrides and carbon dioxide. In order to use and further develop such 'Switch' catalysis, it is important to understand how to monitor the catalysis and characterize the product block copolymers. Here, a step-by-step guide to both the catalysis and the identification of block copolymers is presented. This article is part of a discussion meeting issue ‘Providing sustainable catalytic solutions for a rapidly changing world’.

Polylactic acid (PLA) is a biodegradable and biocompatible polymer that can be applied in the field of packaging and medicine. Its starting substrate is lactic acid and, on this account, PLA can also be considered an ecological material produced from renewable resources. Apart from several advantages, polylactic acid has drawbacks such as brittleness and relatively high glass transition and melting temperatures. However, copolymerization of PLA with other polymers improves PLA features, and a desirable material marked by preferable physical properties can be obtained. Presenting a detailed overview of the accounts on the PLA copolymerization accomplishments is the innovation of this paper. Scientific findings, examples of copolymers (including branched, star, grafted or block macromolecules), and its applications are discussed. As PLA copolymers can be potentially used in pharmaceutical and biomedical areas, the attention of this article is also placed on the advances present in this field of study. Moreover, the subject of PLA synthesis is described. Three methods are given: azeotropic dehydrative condensation, direct poly-condensation, and ring-opening polymerization (ROP), along with its mechanisms. The applied catalyst also has an impact on the end product and should be adequately selected depending on the intended use of the synthesized PLA. Different ways of using stannous octoate (Sn(Oct)2) and examples of the other inorganic and organic catalysts used in PLA synthesis are presented.

Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a (significantly shorter) covalent bond. This volumetric shrinkage can have severe influence on the materials’ properties. One strategy to overcome this volumetric shrinkage is the use of expanding monomers that show volumetric expansion during polymerization reactions. Such monomers exhibit cyclic or even oligocyclic structural motifs with a correspondingly dense atomic packing. During the ring-opening reaction of such monomers, linear structures with atomic packing of lower density are formed, which results in volumetric expansion or at least reduced volumetric shrinkage. This review provides a concise overview of expanding monomers with a focus on the elucidation of structure-property relationships. Preceded by a brief introduction of measuring techniques for the quantification of volumetric changes, the most prominent classes of expanding monomers will be presented and discussed, namely cycloalkanes and cycloalkenes, oxacycles, benzoxazines, as well as thiocyclic compounds. Spiroorthoesters, spiroorthocarbonates, cyclic carbonates, and benzoxazines are particularly highlighted.

A couple of novel crystalline aluminum(III) derivatives containing tridentate Schiff base ligand (HL) and β‐diketones (acetylacetone = acac, benzoylacetone = bnzac, and dibenzoylmethane = dbnz), namely, [Al(L)bnzac] [Al1], [Al(L)dnbz] [Al2], and [Al(L)acac] [Al3], are synthesized and characterized using different spectroscopic techniques and elemental analysis. Single crystal X‐ray diffraction analysis of Al2 and Al3 exhibits hexacoordinated geometry around aluminum center atom which is also confirmed using density functional theory (DFT). The ring‐opening polymerization (ROP) of caprolactone is evaluated to determine the catalytic potential of the complexes Al1–Al3 in the absence and presence of benzyl alcohol (BnOH). The effect of time and temperature is also examined and found that lesser steric effects of the ancillary ligand causes a higher polymerization rate. Gel permeation chromatography (GPC) is used to determine the molecular weight (Mn & Mw) and dispersity (Đ) values of polycaprolactone. Within first 2 h, Al3 exhibits excellent catalytic activity with 99% conversion at 110 °C (MnGPC = 1948 gmol−1, MwGPC = 2865 gmol−1, and Đ = 1.47). An end‐group study is performed using matrix‐assisted laser desorption ionization‐time of flight (MALDI‐TOF) spectrometry, and 1H NMR spectral analysis. Also, PCL is characterized using elemental, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses. First‐order kinetics are found in the monomer aligned with the activated monomer mechanism for the catalysts. Ring‐opening polymerization of ε‐caprolactone using Al(III) heteroleptic complexes containing tridentate Schiff base ligand and β‐diketones is evaluated to determine the catalytic potential of Al(III) complexes in absence as well as in presence of benzyl alcohol.

To achieve next‐generation lithium metal batteries (LMBs) with desirable specific energy and reliability, the electrolyte shown simultaneously high reductive stability toward lithium metal anode and oxidative stability toward high‐voltage cathode is of great importance. Here, we report for the first time that high‐concentration lithium bis(fluorosulfonyl)imide (LiFSI) initiates ring‐opening polymerization of 1,3‐dioxolane in presence of ethylene carbonate and ethylmethyl carbonate to produce in‐situ a novel polymeric concentrated quasi‐solid electrolyte (poly‐CQSE). The unique poly‐CQSE with 10 M LiFSI forms a mixed‐lithiophobic‐conductive LiF‐Li3N solid electrolyte interphase on lithium metal anode, and a F‐rich conformal cathode electrolyte interphase on LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode simultaneously. As a result, the poly‐CQSE not only enables stable Li plating/stripping of metallic Li anode at a sound Coulombic efficiency of 95.3% without dendrite growth, but also enables a stable cycling of the Li||NCM523 quasi‐solid‐state LMB at a capacity retention of 94% over 100 cycles. High‐concentration LiFSI can initiate ring‐opening polymerization of DOL in presence of EC and EMC, forming a new polymeric concentrated quasi‐solid electrolyte, which enables simultaneous stabilization of electrode/electrolyte interphases, leading to a high Coulombic efficiency of 95.3% and excellent cycling performance of 94% capacity retention in Li||NCM523 quasi‐solid‐state lithium metal battery.

The increasing awareness of sustainability has led to enormous growth of the demand for bio‐based and biodegradable polymers such as poly(lactide) (PLA). In industry, polymerization of lactide is currently carried out using tin catalysts (e. g., tin(II) ethyl hexanoate, Sn(Oct)2). Since the catalyst remains in the polymer, it can accumulate in the soil or in the human body after degradation and cause damage due to its toxicity. Therefore, a search for a suitable substitute for this catalyst has been going on for decades. Guanidine metal complexes prove to be excellent catalysts in the polymerization of lactide. They are not only convincing because of their activity and the synthesis of high molar mass polymers, but also show a high robustness against high temperatures, oxidation as well as residual protic impurities in the monomer. Herein, key zinc and iron guanidine complexes are discussed with respect to their apparent rate constant (kapp) and rate constant of propagation (kp), produced molar masses and the mechanism involved. Faster and better: This Minireview presents the latest and most rapid robust catalysts for the ring‐opening polymerization of lactide under industrial conditions. The focus is on the search for a substitute for the currently most commonly used and toxic catalyst Sn(Oct)2 in industry. Numerous ROP‐active guanidine metal complexes are presented, and their activity is compared by analyzing the rate constants of the polymerization.

This review describes recent advances in the synthesis of homopolymers of lactide and related cyclic esters via ring-opening polymerization (ROP) in the presence of metal complexes based on group 1, 2, 4, 12, 13 and 14 metals. Particular attention is paid to the influence of the initiator structure on the properties of the obtaining homo- and copolymers. Also, a separate chapter is devoted to the study of metal complexes in the synthesis of copolymers of lactide and lactones. This review highlights the efforts made over the last ten years or so, and shows how main-group metals have received increasing attention in the field of the polymerization of lactide and related cyclic esters.

This review concentrates on success stories from the synthesis of approved medicines and drug candidates using epoxide chemistry in the development of robust and efficient syntheses at large scale. The focus is on those parts of each synthesis related to the substrate-controlled/diastereoselective and catalytic asymmetric synthesis of epoxide intermediates and their subsequent ring-opening reactions with various nucleophiles. These are described in the form of case studies of high profile pharmaceuticals spanning a diverse range of indications and molecular scaffolds such as heterocycles, terpenes, steroids, peptidomimetics, alkaloids and main stream small molecules. Representative examples include, but are not limited to the antihypertensive diltiazem, the antidepressant reboxetine, the HIV protease inhibitors atazanavir and indinavir, efinaconazole and related triazole antifungals, tasimelteon for sleep disorders, the anticancer agent carfilzomib, the anticoagulant rivaroxaban the antibiotic linezolid and the antiviral oseltamivir. Emphasis is given on aspects of catalytic asymmetric epoxidation employing metals with chiral ligands particularly with the Sharpless and Jacobsen–Katsuki methods as well as organocatalysts such as the chiral ketones of Shi and Yang, Pages’s chiral iminium salts and typical chiral phase transfer agents.

This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.

In this study, a series of novel homopolymers based on N-Boc-protected 2-(aminopentyl)-2-oxazoline (P(PentNHgocOXx)) were synthesized via microwave-assisted cationic ring-opening polymerization (CROP), achieving high monomer conversions (up to 100%) and low dispersity values (D = 1.08-1.30). The resulting polymers were quantitatively deprotected using TFA/DCM, followed by ion exchange to yield amino-functionalized poly(2-oxazoline)s (P(PentNH,0x)). Comprehensive characterization of the polymers confirmed successful deprotection without polymer degradation, preservation of low dispersity, and the formation of nanoscale aggregates in aqueous solutions falling within the size range of 140-152 nm, suitable, for biomedical applications. Cytotoxicity assays demonstrated that the polymers are non-toxic to human dermal fibroblasts, maintaining cell viability above 70% even at higher concentrations and extended incubation times. These findings highlight the potential of P(PentNH20x) as promising, biocompatible candidates for biomedical and nanotherapeutic applications.