Poly(2-oxazoline)s Functionalized with Palladium Carbene Complexes: Soluble, Amphiphilic Polymer Supports for C−C Coupling Reactions in Water

From a single helix to a helical porous metalloenzyme catalyst based on temperature sensitive polyionic liquids

It is a challenging task to construct helical structures through the assembly of achiral polymers.

Ferrocene containing redox-responsive poly(2-oxazoline)s

A new monomer, 2-ferrocene-ethyl-2-oxazoline, was copolymerized with 2-alkyl-2-oxazolines. The cationic ring opening polymerization (CROP) of 2-oxazolines allows the synthesis of well-defined copolymers with adjustable molar masses as well as end-group control, which was also evident from kinetic studies. The utilization of this new comonomer led to redox-active polymers as proven by UV-VIS-measurements and cyclic-voltammetry.

Recent Advances in the Synthesis and Application of Polymer Compartments for Catalysis

Catalysis is one of the most important processes in nature, science, and technology, that enables the energy efficient synthesis of essential organic compounds, pharmaceutically active substances, and molecular energy sources. In nature, catalytic reactions typically occur in aqueous environments involving multiple catalytic sites. To prevent the deactivation of catalysts in water or avoid unwanted cross-reactions, catalysts are often site-isolated in nanopockets or separately stored in compartments. These concepts have inspired the design of a range of synthetic nanoreactors that allow otherwise unfeasible catalytic reactions in aqueous environments. Since the field of nanoreactors is evolving rapidly, we here summarize-from a personal perspective-prominent and recent examples for polymer nanoreactors with emphasis on their synthesis and their ability to catalyze reactions in dispersion. Examples comprise the incorporation of catalytic sites into hydrophobic nanodomains of single chain polymer nanoparticles, molecular polymer nanoparticles, and block copolymer micelles and vesicles. We focus on catalytic reactions mediated by transition metal and organocatalysts, and the separate storage of multiple catalysts for one-pot cascade reactions. Efforts devoted to the field of nanoreactors are relevant for catalytic chemistry and nanotechnology, as well as the synthesis of pharmaceutical and natural compounds. Optimized nanoreactors will aid in the development of more potent catalytic systems for green and fast reaction sequences contributing to sustainable chemistry by reducing waste of solvents, reagents, and energy.

Chemically grafting nanoscale UIO-66 onto polypyrrole nanotubes for long-life lithium–sulfur batteries

Chemical grafting of nanoscale UIO-66 onto polypyrrole nanotubes (sesame-like PPyNTs@UIO-66) was performed successfully, and the corresponding PPyNT@UIO-66-S cathode greatly improves the cycling performance of lithium–sulfur batteries.

C–C couplings in water by micellar catalysis at low loadings from a recyclable polymer-supported Pd(ii)–NHC nanocatalyst

A robust and recyclable polymer-supported Pd(ii)–NHC₂ nanocatalyst enables highly efficient micellar catalysis of the Suzuki–Miyaura reaction at low loadings with a broad substrate scope.

Size-Dependent Catalytic Activity and Fate of Palladium Nanoparticles in Suzuki-Miyaura Coupling Reactions

Stable, catalytically active palladium nanoparticles of various average diameters (1.9-7.4 nm) have been synthesized and characterized by X-ray diffraction, spectroscopy, and microscopy techniques to demonstrate remarkable size-dependent and renewed catalytic activity toward the Suzuki-Miyaura coupling reaction in green protocol. The catalytic activity is found to depend on the amount of the reducing agent, stabilizer-precursor ratio, solvent composition, and aryl halides used. The product obtained by this reaction is characterized by ¹H NMR, ¹³C NMR, and IR spectroscopy analyses. A newly developed kinetic equation illustrates that while the catalyst particles of the lowest dimension are gradually exposed to the reactants and hence activated due to partial removal of capping polymer from the catalyst surface, others are deactivated due to agglomeration during the progress of the reaction, as conformed by the microscopic profiles of the used and unused catalysts.

Preparation of Thermo-Responsive and Cross-Linked Fluorinated Nanoparticles via RAFT-Mediated Aqueous Polymerization in Nanoreactors

In this work, a thermo-responsive and cross-linked fluoropolymer poly(2,2,2-Trifluoroethyl) methacrylate (PTFEMA) was successfully prepared by reversible addition-fragmentation chain transfer (RAFT) mediated aqueous polymerization with a thermo-responsive diblock poly(dimethylacrylamide-b-N-isopropylacrylamide) (PDMA-b-PNIPAM) that performed a dual function as both a nanoreactor and macro-RAFT agent. The cross-linked polymer particles proved to be in a spherical-like structure of about 50 nm in diameter and with a relatively narrow particle size distribution. ¹H-NMR and ¹⁹F-NMR spectra showed that thermo-responsive diblock P(DMA-b-NIPAM) and cross-linked PTFEMA particles were successfully synthesized. Influence of the amount of ammonium persulfate (APS), the molar ratio of monomers to RAFT agent, influence of the amount of cross-linker on aqueous polymerization and thermo-responsive characterization of the particles are investigated. Monomer conversion increased from 44% to 94% with increasing the molar ratio of APS and P(DMA-b-NIPAM) from 1:9 to1:3. As the reaction proceeded, the particle size increased from 29 to 49 nm due to the consumption of TFEMA monomer. The size of cross-linked nanoparticles sharply decreased from 50.3 to 40.5 nm over the temperature range 14–44 °C, suggesting good temperature sensitivity for these nanoparticles.

Chemoenzymatic one-pot reaction of noncompatible catalysts: combining enzymatic ester hydrolysis with Cu(i)/bipyridine catalyzed oxidation in aqueous medium

Combination of a lipase (CALB) with a Cu/bipyridine catalyst for environmentally benign synthesis of aldehydes from their corresponding esters.

Bipyridine-functionalized amphiphilic block copolymers as support materials for the aerobic oxidation of primary alcohols in aqueous media

A micellar catalytic version of the aerobic oxidation of primary alcohols was successfully developed based on core-functionalized polymer nanoparticles.

Clickable Amphiphilic Triblock Copolymers

Amphiphilic polymers have recently garnered much attention due to their potential use in drug-delivery and other biomedical applications. A modular synthesis of these polymers is extremely desirable since it offers precise individual block characterization and increased yields. We present here for the first time a modular synthesis of poly(oxazoline)-poly(siloxane)-poly(oxazoline) block copolymers that have been clicked together using the copper-catalyzed azide-alkyne cycloaddition reaction. Various click methodologies for the synthesis of these polymers have been carefully evaluated and optimized. The approach using copper nanoparticles was found to be the most optimal among the methods evaluated. Furthermore, these results were extended to allow for a reactive Si-H group-based siloxane middle block to be successfully clicked. This enables the design of more complex amphiphilic block copolymers that have additional functionality, such as stimuli responsiveness, to be synthesized via a simple hydrosilylation reaction.

Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: synthesis, metal immobilization and use in hydroformylation under micellar conditions

Norborn-5-ene-(N,N-dipyrid-2-yl)carbamide (M1) was copolymerized with exo,exo-[2-(3-ethoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-en-2-carbonyloxy)ethyl]trimethylammonium iodide (M2) using the Schrock catalyst Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(OCMe(CF₃)₂)₂[Mo] to yield poly(M1-b-M2). In water, poly(M1-b-M2) forms micelles with a critical micelle-forming concentration (cmc) of 2.8 x 10⁻⁶ mol L⁻¹; Reaction of poly(M1-b-M2) with [Rh(COD)Cl]₂ (COD = cycloocta-1,5-diene) yields the Rh(I)-loaded block copolymer poly(M1-b-M2)-Rh containing 18 mg of Rh(I)/g of block copolymer with a cmc of 2.2 x 10⁻⁶ mol L⁻¹. The Rh-loaded polymer was used for the hydroformylation of 1-octene under micellar conditions. The data obtained were compared to those obtained with a monomeric analogue, i.e. CH₃CON(Py)₂RhCl(COD) (C1, Py = 2-pyridyl). Using the polymer-supported catalyst under micellar conditions, a significant increase in selectivity, i.e. an increase in the n:iso ratio was accomplished, which could be further enhanced by the addition of excess ligand, e.g., triphenylphosphite. Special features of the micellar catalytic set up are discussed.