Andreas F. M. Kilbinger

Ring-opening metathesis polymerization (ROMP) is a powerful method to generate well-defined polymers. However, conventional ROMP is neither environmentally benign nor sustainable, as it typically uses chlorinated organic solvents and high loadings of ruthenium-initiators which can result in residual metal contamination and associated toxicity. Herein, we report a sustainable and efficient catalytic ROMP methodology conducted either in water at pH 2 or in a 9:1 water/THF mixture containing 0.1 M NaCl using catalytic amounts of Ru-complexes. Despite the inherent challenges of aqueous ROMP, including inefficient Ru-complex initiation and poor end-group fidelity, our approach enables the living synthesis of well-defined ROMP polymers with excellent chain-end functionality, and moderate control over molar mass while using substoichiometric amounts of the Ru-complex. The preserved chain-end fidelity enables efficient protein–polymer conjugation. Moreover, our methodology provides efficient access to thermoresponsive polymers under aqueous conditions and enables the synthesis of poly(ethylene glycol) (PEG)-based block copolymers, which are difficult to access using conventional aqueous ROMP. This work demonstrates a green and scalable platform for well-defined polymer synthesis in water and expands the scope of ROMP toward environmentally benign and biologically relevant applications.

Helical aromatic oligoamides were synthesized via a polymerization strategy from amino acid-derived monomers to probe side-chain steric effects on helical chirality.

Biology uses folded polymeric chains to perform complex tasks, from scaffolding catalytic enzymes to creating highly selective transmembrane channels. Aquaporins are a class of transmembrane channels that can strictly exclude the transport of salts, whilst allowing exceptional rates of water transport (up to 3 x 10^9 water molecules per channel per second). These biological water channels, and the recently described artificial water channels they have inspired, provide a potential route to less energy intensive desalination technologies – a critical emerging need. Herein, we report the design of extensively fluorinated aramid polymers synthesised by living polymerisation, which fold into discrete single chain nanoparticles with a well-defined, continuous, internal lumen. These are stabilised by continuous F-H-F three-centre hydrogen bonds, which enable robust folding, and provide a polyfluorinated surface. These nanoparticles have a defined function – selective transmembrane transport of water, with exceptionally high rates (up to 4.5 x 10^10 water molecules per channel per second), exceeding those of the natural Aquaporins, whilst retaining excellent salt rejection.

We report herein the living polymerization of an amphiphilic helical aramid diblock copolymer made possible by the utilization of reagent PHOS3. Two monomers, 2,4-bis((2,5,8,11-tetraoxapentadecan-15-yl)oxy)-5-aminobenzoic acid and 5-amino-2,4-difluorobenzoic acid, were used to build the hydrophilic and hydrophobic blocks respectively. The diblock copolymer was characterized by NMR and GPC/SEC and its aggregation behavior was investigated with atomic force microscopy (AFM), multi-angle depolarized dynamic light scattering (DDLS), and small angle X-rays scattering (SAXS). The analysis strongly suggests the diblock copolymer self-assembles to form elongated, tube-like structures in water.

Tubular structures with nanosized pores have shown remarkable applications in areas such as ion transport and water filtration, but their development is often hindered by challenges including low yields, limited functionalization, and poor uniformity. Herein, we present a new series of macrocycles with tuneable diameters and helical foldamers featuring customizable peripheral side chains. The macrocycles, with diameters ranging from 0.8 to 1.4 nm, were synthesized in moderate to good yields using a one-pot method. Solid-state analysis revealed that these macrocycles form nanochannels, highlighting their potential applications in areas such as molecular recognition and artificial water channels (AWCs). Additionally, we synthesized helical aromatic amide polymers with narrow dispersities via a living chain-growth process. Our strategy enables the incorporation of diverse functional groups, including ethers, esters, acids, and amides, on the outer surfaces of the macrocycles or synthetic nanotubes. Circular dichroism (CD) spectroscopy confirmed the helical conformations of the polymers in solution. These macrocycles and foldamers present exciting opportunities for designing bioinspired membrane channels and functional nanotubes with tuneable hydrophobicity and cavity sizes, paving the way for innovative applications in nanotechnology and materials science.

We employ a living polymerization strategy and a crescent-shaped monomer to synthesize large aromatic amide helices with cavity sizes exceeding 1 nm.

The nanoconfinement of lipid self-assembled structures offers a dynamic environment for chemical reactions. It enables the integration of regents of various polarities, their alignment at the lipid/water interface for regiospecific reactions, and tailored reaction dimensions from restricted diffusion in the nanoconfinement. However, the effects of monomer integration and polymerization on the self-assembly structure and reaction products remain to be fully understood. Here, we report the photoinitiated polymerization of hydroxyethyl acrylate (HEA) within the inverse bicontinuous cubic structure of glycerol monooleate (GMO), yielding biocompatible hybrid materials. The initial structures are formed in bulk and as thin films on silicon wafers through the self-assembly of GMO molecules with water. Using small-angle X-ray scattering (SAXS) and grazing incidence (GI)SAXS, we find that HEA actively integrates into the lipid-water interface, modifying the self-assembled packing geometries. Photopolymerization triggered structural transformations and changes in orientation relative to the substrate surface. Nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography reveal larger polymer sizes and smaller polydispersity under nanoconfined conditions compared to polymerization in water. These findings enhance the understanding of self-assembled structures as reaction nanoconfinements and establish a foundation for advanced material design.