Reversible Activity Modulation of Surface-Attached Grubbs Second Generation Type Catalysts Using Redox-Responsive Polymers

Abstract

Redox-responsive polyvinylferrocene-grafted silica nanoparticles have been used for modulating the catalytic activity of surface-attached Grubbs second generation type catalysts for the ring-opening metathesis polymerization (ROMP) of norbornene monomer. A facile and very efficient protocol for the modification of living polyvinylferrocene chains was developed to introduce a suitable functional group for the intended “grafting onto” approach. Grafted particles were characterized by using TEM, SEM/energy dispersive X-ray spectroscopy (EDS), XPS, small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and cyclic voltammetry, revealing both the presence of redox-responsive polymers and the presence of Grubbs catalyst in the particle exterior. Chemical oxidation protocols for immobilized polymers were applied to deactivate surface-attached catalysts in ROMP protocols, while chemical in situ reduction immediately led to catalyst’s reactivation.

Polymer‐Modified Mesoporous Silica Thin Films for Redox‐Mediated Selective Membrane Gating

“…[ 51 ] Triethoxy functionalized polyvinylferrocenes (PVFc-TEOS) were synthesized via anionic polymerization as recently reported. [ 49 ] Instrumentation : Standard SEC was performed with tetrahydrofuran (THF) as the mobile phase (fl ow rate 1 mL min −1 ) on a SDV column set from PSS (SDV 1000, SDV 100000, SDV 1000000) at 30 ° C. Calibration was carried out using PS standards (from Polymer Standard Service, Mainz). For the SEC-MALLS experiments, a system composed of a Waters 515 pump (Waters, Milford, CT), a TSP AS100 autosampler, a Waters column oven, a Waters 486 UV detector operating at 254 nm, a Waters 410 RI-detector, and a DAWN DSP light scattering detector (Wyatt Technology, Santa Barbara, CA) was used.…”

“…Additionally, exclusion of ions. [ 58,59 ] To manipulate the permselective and the chemical properties by using external redox stimuli, we immobilized redox-responsive polymers to the mesoporous silica membrane by using two synthetic approaches ( Figure 2 ): fi rstly, a grafting to procedure by using a PVFc carrying a triethoxysilane end group with a molecular weight of 2700 g mol −1 ( M w ) for the PVFc precursor [ 49 ] was applied (Figure 2 a). Secondly, we used a grafting from approach by using a surface initiated ATRP polymerization of FcMA mono mer after immobilizing 3-(2-bromo iso butyrate)propyl trichlorosilane as initiator (Figure 2 b).…”

“…While oxidizing the ferrocene moieties (electro)chemically, the polymer chains undergo a remarkable transition from hydrophobic to hydrophilic accompanied by an induction of charge. [ 40,[43][44][45][46] The ferrocene oxidation/reduction cycles could be utilized for controlled release of organics from gels, [ 47 ] for applications as composite colloidal crystal fi lms, [ 46 ] for responsive release of a dye from patchy nanocapsules, [ 48 ] for catalysis modulation, [ 49 ] or for switching surface wettability. [ 50 ] Here, we report the functionalization of an ordered mesoporous silica thin fi lm with redox-responsive poly(2-(methacryloyloxy)ethyl ferrocenecarboxylate) (PFcMA) and end functionalized polyvinylferrocene (PVFc).…”

Porous Carbons – Hyperbranched Polymers – Polymer Solvation

“…The AB 2 monomers were prepared by repeating a series of conversions of the hydroxy group to the triflate, crosscoupling of the triflate with ( p-methoxythiophenyl) boronic acid, reduction of the carbonyl groups, and subsequent conversion of the methylthio group to a thiol group. The AB 2 monomers self-condensed to form different hb-PAEKs and the T g was 175,197, or 215 C, depending on whether the repeat unit structure contained biphenyl, terphenyl, or quadriphenyl units in the polymer backbone. Baek and Tan [154] improved the procedure for preparation of 3,5-bis (4-fluorobenzoyl)phenol (AB 2 monomer) at the intermediate step by the use of an acetyl group instead of a methyl group as the protecting group for the hydroxyl function of the AB 2 monomer.…”

Metallopolymer-Based Shape Anisotropic Nanoparticles

“…21,23−26 Since this oxidation/reduction cycle is accompanied by a transition from a hydrophobic to a hydrophilic state, 27−29 such redox-active polymers have been utilized for a variety of applications, for example, for releasing dyes from redox-responsive nanocapsules, 29−31 for switching the surface wettability and membrane gating, 32−34 for addressing metallopolymer-based colloidal crystals or inverse opal films, 35,36 or for reversible activity modulation of immobilized catalysts. 37 From a morphology viewpoint, block copolymers based on semicrystalline 38 PFS have also attracted significant attention for the preparation of well-defined nanostructures both in the bulk state and in selective solvents by crystallization driven selfassembly (CDSA). 39− 45 Taking advantage of these unique attributes for ferrocene containing polymers, we propose to investigate the particle constrained phase-separation of poly(ferrocenylsilane)-b-poly-(2-vinylpyridine) (PFS-b-P2VP) block copolymers leading to two new types of shape anisotropic nanoparticles: (1) ellipsoidal nanoparticles with an axially stacked lamellar structure and (2) flattened nanosheets (or convex lenses) with a hexagonally packed cylinder structure perpendicular to the long axis.…”