Helmut Schlaad

Polyacetals based on levoglucosenol and levoglucosenyl alkyl/silyl ethers, which were obtained by ring-opening metathesis polymerization, were analyzed according to their microstructure, i.e., head−tail, head−head, and tail−tail monomer sequence, using 1H and 13C nuclear magnetic resonance (NMR) and two-dimensional NMR spectroscopy including 1H−1H total correlation spectroscopy NMR measurements. For polylevoglucosenol, the monomer sequence along the polymer chain was found to be random, while for poly(levoglucosenyl alkyl/silyl ether)s, it was shifted to a predominantly head−tail sequence, depending on the bulkiness of the side chain. Especially, branched isopropyl and trimethylsilyl substituents promoted the formation of polyacetals with exclusively head−tail units. Accordingly, a highly stereoregular polylevoglucosenol sample was accessible for the first time by deprotection of poly(levoglucosenyl trimethylsilyl ether) and was further analyzed according to its thermal properties. However, despite the perfect stereoregularity, crystallization of the polylevoglucosenol was neither observed in differential scanning calorimetry experiments nor in proton time-domain NMR experiments on an even longer timescale upon slow cooling. The latter revealed the signature and timescale of the glassy α relaxation and further demonstrated a plasticizer effect related to residual monomer in the sample.

Performing organic photoredox reactions in water remains challenging because most catalysts cannot simultaneously solubilize substrates, control nanoscale organization, and maintain activity under aqueous conditions. We report a photoredox-active polyelectrolyte based on a polydehydroalanine (PDha) backbone covalently functionalized with polypyridyl complexes to address some of these limitations. The copolymer undergoes substrate-triggered self-assembly in water, forming photocatalytically active spherical colloidal nanostructures (∼30 nm), as confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The assemblies efficiently catalyze the hydroxylation of arylboronic acids, a representative water-insoluble photoredox transformation. Mechanistic studies using UV-visible spectroscopy, Raman spectroscopy, time-resolved emission spectroscopy, electrochemistry, and density functional theory (DFT) indicate that dual hydrogen bonding between PDha carboxylates and arylboronic acids governs both self-assembly and catalytic performance. The nanostructures retain high activity over multiple cycles. These findings establish adaptive polymer self-assembly as a general strategy for creating enzyme-like, water-compatible photoredox systems and provide a platform for transferring organic photoredox chemistry into aqueous media.

Catechol‐containing poly(2‐isopropyl‐2‐oxazoline)s (PiPOx) were obtained either by functionalization of partially hydrolyzed PiPOx with 3,4‐dimethoxybenzoyl chloride or by microwave‐assisted cationic ring‐opening copolymerization of 2‐isopropyl‐2‐oxazoline with 2‐(3,4‐dimethoxyphenyl)‐2‐oxazoline, followed by quantitative deprotection of methylated catechols. All synthesized polymers were soluble in aqueous salt solutions at room temperature and showed thermoresponsive LCST behavior. The cloud point temperature ( T _CP ) remained virtually unchanged in the presence of different cations, while it was strongly affected by chaotropic and kosmotropic anions, which is in line with the Hofmeister series. Intriguingly, T _CP was lower for the catechol‐containing PiPOx as compared to the protected precursor copolymer and PiPOx, which is rationalized by hydrogen bonding interactions between catechol and tertiary amide units of the polymer backbone, as indicated by Raman spectroscopy, decreasing the hydration level of the polymer.

Micellar catalysis offers a sustainable and effective alternative to traditional systems. This study introduces a micellar platform based on the amphiphilic diblock copolypeptoid poly(N-methyl glycine)-block-poly(N-n-propyl glycine) for direct arene cyanation in water. The polymer was used to encapsulate the photoredox catalyst 3,6-di-tert-butyl-9-mesityl-10-phenylacridinium tetrafluoroborate (Mes-Acr-Ph⁺), forming core-shell nanostructures, as confirmed by dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM). Under visible light irradiation, micellar core confinement activates the catalytic performance of Mes-Acr-Ph⁺, enabling selective C-H cyanation of diverse arenes in water. Recycling experiments demonstrate the stability and reusability of the micelles, highlighting their potential for scalable photoredox applications. This strategy advances aqueous photoredox catalysis by addressing longstanding challenges in catalyst solubility, reactivity, aggregation, close proximity, and reaction control.

The kinetics of anionic polymerization of β‐myrcene initiated by sec‐butyllithium were examined in saturated and unsaturated hydrocarbon solvents, i.e. cyclohexane, cyclohexene, 4‐vinylcyclohexene and dl‐limonene. Polymerizations usually proceeded in a living manner, i.e. in the absence of termination and chain transfer reactions, in all solvents, to produce well‐defined polymyrcenes with high content (>85%) of cis‐1,4 units. However, polymyrcenyllithium chains exhibited limited long‐term stability in 4‐vinylcyclohexene solution, most probably due to chain transfer to solvent. Reaction orders with respect to the concentration of active chains were found to be one‐quarter in cyclohexane increasing to one‐half in unsaturated solvents, indicating that the polymyrcenyllithium chains are present as tetrameric or dimeric associates, respectively. Apparent activation energies were found to be 81 kJ mol⁻¹ in cyclohexane and 77 kJ mol⁻¹ in dl‐limonene solution, which are close to the values obtained by quantum chemical calculations. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Polymyrcenyllithium chains in dl-limonene solution are present as dimeric associates and not as single chains.

A small series of copoly(α,l-glutamic acid/dl-allylglycine)s with the same chain length and allylglycine content (∼10 mol %) but different spatial distribution of allylglycine units was synthesized and subsequently glycosylated via thiol-ene chemistry. Dilute aqueous copolypeptide solutions (0.1 wt %, physiological saline) were analyzed by circular dichroism spectroscopy, dynamic light scattering, and cryogenic transmission electron microscopy. The copolypeptides adopted a random coil or α-helix conformation, depending on solution pH, and the glycosylated residues either distorted or enhanced the folding into an α-helix depending on their location and spatial distribution along the chain. However, regardless of their secondary structure and degree of charging, all partially glycosylated copolypeptides self-assembled into 3D spherical structures, supposedly driven by a hydrophilic effect promoting microphase separation into glucose-rich and glutamate-rich domains.

Elemental sulfur, a waste product of the oil refinement process, represents a promising raw material for the synthesis of degradable polymers. We show that simple lithium alkoxides facilitate the polymerisation of elemental sulfur S₈ with industrially relevant propylene oxide (PO) and CS₂ (a base chemical sourced from waste S₈ itself) to give poly(monothiocarbonate‐alt‐S_x) in which x can be controlled by the amount of supplied sulfur. The in situ generation of thiolate intermediates obtained by a rearrangement, which follows CS₂ and PO incorporation, allows to combine S₈ and epoxides into one polymer sequence that would otherwise not be possible. Mechanistic investigations reveal that alkyl oligosulfide intermediates from S₈ ring opening and sulfur chain length equilibration represent the better nucleophiles for inserting the next PO if compared to the trithiocarbonates obtained from the competing CS₂ addition, which causes the sequence selectivity. The polymers can be crosslinked in situ with multifunctional thiols to yield reprocessable and degradable networks. Our report demonstrates how mechanistic understanding allows to combine intrinsically incompatible building blocks for sulfur waste utilisation.