Explore the vast range of titles available.

Most synthetic polymers are made from petroleum and their production is currently not sustainable. RAFT polymerization has emerged as a powerful technique to control the synthesis of such polymers, thus expanding further their applications. This Review discusses the sustainability of RAFT in terms of process and materials. Reversible addition-fragmentation chain-transfer (RAFT) polymerization has revolutionized the field of polymer synthesis as a versatile tool for the production of complex polymeric architectures. As for all chemical processes, research and development in RAFT have to focus on the design and application of chemical products and processes that have a minimum environmental impact, and follow the principles of 'green' chemistry. In this Review, we summarize some of the green features of the RAFT process, and review the recent advances in the production of degradable polymers obtained from RAFT polymerization. Its use to modify biodegradable and renewable inorganic and organic materials to yield more functional products with enhanced applications is also covered. RAFT is a promising candidate for answering both the increasing need of modern society to employ highly functional polymeric materials and the global requirements for developing sustainable chemicals and processes.

Hydroxyl radical (OH) is a key oxidant that triggers atmospheric oxidation chemistry in both gas and aqueous phases. The current understanding of its aqueous sources is mainly based on known bulk (photo)chemical processes, uptake from gaseous OH, or related to interfacial O₃ and NO₃ radical-driven chemistry. Here, we present experimental evidence that OH radicals are spontaneously produced at the air—water interface of aqueous droplets in the dark and the absence of known precursors, possibly due to the strong electric field that forms at such interfaces. The measured OH production rates in atmospherically relevant droplets are comparable to or significantly higher than those from known aqueous bulk sources, especially in the dark. As aqueous droplets are ubiquitous in the troposphere, this interfacial source of OH radicals should significantly impact atmospheric multiphase oxidation chemistry, with substantial implications on air quality, climate, and health.

Self-assembling peptides have the ability to spontaneously aggregate into large ordered structures. The reversibility of the peptide hydrogen bonded supramolecular assembly make them tunable to a host of different applications, although it leaves them highly dynamic and prone to disassembly at the low concentration needed for biological applications. Here we demonstrate that a secondary hydrophobic interaction, near the peptide core, can stabilise the highly dynamic peptide bonds, without losing the vital solubility of the systems in aqueous conditions. This hierarchical self-assembly process can be used to stabilise a range of different β-sheet hydrogen bonded architectures. Reversibility of peptide hydrogen bonded supramolecular assemblies makes them tunable but highly dynamic and prone to disassembly at the low concentration. Here the authors show a secondary hydrophobic interaction, near the peptide core that stabilises the peptide bonds, without losing the solubility of the systems in aqueous conditions.

The Staphylococcus aureus type VII secretion system (T7SS) exports several proteins that are pivotal for bacterial virulence. The mechanisms underlying T7SS-mediated staphylococcal survival during infection nevertheless remain unclear. Here we report that S. aureus lacking T7SS components are more susceptible to host-derived antimicrobial fatty acids. Unsaturated fatty acids such as linoleic acid (LA) elicited an increased inhibition of S. aureus mutants lacking T7SS effectors EsxC, EsxA and EsxB, or the membrane-bound ATPase EssC, compared to the wild-type (WT). T7SS mutants generated in different S. aureus s train backgrounds also displayed an increased sensitivity to LA. Analysis of bacterial membrane lipid profiles revealed that the esxC mutant was less able to incorporate LA into its membrane phospholipids. Although the ability to bind labelled LA did not differ between the WT and mutant strains, LA induced more cell membrane damage in the T7SS mutants compared to the WT. Furthermore, proteomic analyses of WT and mutant cell fractions revealed that, in addition to compromising membranes, T7SS defects induce oxidative stress and hamper their response to LA challenge. Thus, our findings indicate that T7SS contribute to maintaining S. aureus membrane integrity and homeostasis when bacteria encounter antimicrobial fatty acids.

Self-assembled nanotubular structures have numerous potential applications but these are limited by a lack of control over size and functionality. Controlling these features at the molecular level may allow realization of the potential of such structures. Here we report a new generation of self-assembled cyclic peptide–polymer nanotubes with dual functionality in the form of either a Janus or mixed polymeric corona. A ‘relay’ synthetic strategy is used to prepare nanotubes with a demixing or mixing polymeric corona. Nanotube structure is assessed in solution using 1 H– 1 H nuclear Overhauser effect spectroscopy NMR, and in bulk using differential scanning calorimetry. The Janus nanotubes form artificial pores in model phospholipid bilayers. These molecules provide a viable pathway for the development of intriguing nanotubular structures with dual functionality via a demixing or a mixing polymeric corona and may provide new avenues for the creation of synthetic transmembrane protein channel mimics. Cyclic peptide–polymer nanotubes are promising functional materials. Here, the authors present asymmetric cyclic peptide–polymer conjugates that form nanotubes of controlled length with dual functionality via a mixing or demixing polymeric corona, the latter leading to Janus nanotubes.

The properties and applications of biomacromolecules, for example proteins, can be enhanced by the covalent attachment of synthetic polymers. This Review discusses the modification of these biomacromolecules with stimuli-responsive polymers. The properties and applications of biomacromolecules, for example proteins, can be enhanced by the covalent attachment of synthetic polymers. This Review discusses the modification of these biomacromolecules with stimuli-responsive polymers.

Organic aerosols (OAs) play a critical role in the atmosphere by directly altering human health and the climate. Understanding the formation and evolution of OAs as well as their physicochemical properties requires a detailed characterization of their chemical composition. Despite advanced analytical techniques developed within the last decades, the real-time online measurement of atmospheric particles remains challenging and is affected by different artifacts (i.e., thermal decomposition, fragmentation, wall loss). In this work, we introduce the newly designed wall-free particle evaporator (WALL-E) coupled with a chemical ionization mass spectrometer (CIMS), using bromide (Br−) as the reagent ion. We comprehensively evaluate the performance of the WALL-E system, demonstrating its ability to evaporate particles while maintaining the integrity of the compounds composing the particles (i.e., minimal thermal decomposition). To demonstrate WALL-E's performance, the composition of aerosol particles formed from α-pinene ozonolysis in the presence of SO2 is characterized. In addition, by applying the scan declustering method, we can now provide a quantification of the different species present in the condensed phase, e.g., C10H16O4 84 ng m−3, C19H28O7 7 ng m−3 for a total secondary organic aerosol (SOA) mass of 1 µg m−3. While dimers exhibit higher sensitivities, they account for only 14 %–18 % of the total particle mass, which is considerably lower than their signal fractions (23 %–29 %). This suggests a potential overestimation of the dimer contributions when relying solely on signal fractions. In addition, a volatility analysis using thermograms reveals a clear relationship between T50 and compound saturation vapor pressure (C∗), with lower-volatility species desorbing at higher temperatures. In addition, the measured T50 (the temperature at which 50 % of a compound evaporates) for α-pinene-derived SOA products agree well with theoretical volatility estimation models (e.g., SIMPOL). Overall, this study demonstrates that the WALL-E system coupled with a CIMS is a promising technique for real-time particle characterization (i.e., composition, quantification, and volatility) of atmospheric aerosols.

A long-standing challenge in polymer chemistry has been to prepare synthetic polymers with not only well-defined molecular weight, but also precisely controlled microstructure in terms of the distribution of monomeric units along the chain. Here we describe a simple and scalable method that enables the synthesis of sequence-controlled multiblock copolymers with precisely defined high-order structures, covering a wide range of functional groups. We develop a one-pot, multistep sequential polymerization process with yields >99%, giving access to a wide range of such multifunctional multiblock copolymers. To illustrate the enormous potential of this approach, we describe the synthesis of a dodecablock copolymer, a functional hexablock copolymer and an icosablock (20 blocks) copolymer, which represents the largest number of blocks seen to date, all of very narrow molecular weight distribution for such complex structures. We believe this approach paves the way to the design and synthesis of a new generation of synthetic polymers. Sequence control of multiblock copolymers is a difficult task for polymer chemistry. Here the authors report a simple radical method that allows the synthesis of well-defined block copolymers with a wide range of functional groups, including a 20-unit multiblock copolymer.

Precise control over the location of monomers in a polymer chain has been described as the ‘Holy Grail’ of polymer synthesis. Controlled chain growth polymerization techniques have brought this goal closer, allowing the preparation of multiblock copolymers with ordered sequences of functional monomers. Such structures have promising applications ranging from medicine to materials engineering. Here we show, however, that the statistical nature of chain growth polymerization places strong limits on the control that can be obtained. We demonstrate that monomer locations are distributed according to surprisingly simple laws related to the Poisson or beta distributions. The degree of control is quantified in terms of the yield of the desired structure and the standard deviation of the appropriate distribution, allowing comparison between different synthetic techniques. This analysis establishes experimental requirements for the design of polymeric chains with controlled sequence of functionalities, which balance precise control of structure with simplicity of synthesis. Chemists increasingly seek to control monomer sequencing in aperiodic copolymers. Here, the authors show that the statistical nature of chain growth strongly limits the achievable control, and establish parameters for polymer design that balance precise control with simplicity of synthesis.