Mark A. Hempenius

Poly(arylene ether ketone)s (PAEKs) are the most commonly known high‐performance materials used for ion exchange and fuel cell membranes. Described here is the design of novel sulfonated PAEKs (SPAEKs) and nonsulfonated PAEKs containing crown ether units in the main chain, which can be used in sensing applications and ion‐selective membranes. To this end, 4,4′(5′)‐di(hydroxybenzo)‐18‐crown‐6 was synthesized and used as monomer in a step growth polymerization to form crown ether‐containing PAEKs and SPAEKs. The successful synthesis of PAEKs containing 18‐crown‐6 and sulfonate groups was confirmed by gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Membranes are fabricated from the sulfonated polymers. Potassium ion transport properties of the SPAEK and crown ether‐containing SPAEK membranes are assessed by diffusion dialysis. Potassium ion diffusion in the crown ether‐containing SPAEK membranes is almost four times lower than K⁺ diffusion in the native polymer membranes, without crown ether. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2786–2793

A hydrogel composed of poly(ferrocenylsilane) polyanion and poly(ethylene glycol) chains was used to form relatively well-defined, unaggregated Pd(0) nanoparticles (8.2 ± 2.2 nm) from K ₂ PdCl ₄ salts.

Molecular bottlebrushes, possessing a redox-responsive poly(ferrocenylsilane) (PFS) backbone and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) side chains, distributed homogeneously or as a gradient along the PFS main chain, were synthesized. Attachment of the PNIPAM chains via azide–alkyne click chemistry, or grafting from a PFS macroinitiator backbone by ATRP, resulted in cylindrical shaped molecular bottlebrushes. We found the bottlebrushes to be both redox and temperature responsive, with little influence of one responsiveness on the other. In an aqueous environment above 32 °C the bottlebrushes collapsed to 70% of their original size due to the temperature sensitive side chains, and reversibly recovered their initial size upon cooling as revealed by Dynamic Light Scattering (DLS). Cyclic voltammograms showed electrochemical behavior typical of well solvated, single PFS chains. The backbone of the deposited molecules was in close proximity to the highly ordered pyrolytic graphite (HOPG) electrode surface and was accessible to the supporting electrolyte owing to the presence of the hydrophilic PNIPAM side chains. The bottlebrush molecules were deposited on HOPG surfaces for direct molecular visualization by atomic force microscopy (AFM). Molecular size data obtained by DLS and AFM showed good agreement. The bottlebrushes, reported here, are excellent candidates as addressable components for future devices e.g. to carry and deliver molecular payloads.

Novel hydrogels composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and redox-responsive poly(ferrocenylsilane) (PFS) macromolecules were formed by photopolymerization. PFS chains bearing acrylate side groups were copolymerized with NIPAM and N,N′-methylenebisacrylamide in tetrahydrofuran in a predetermined ratio under ultraviolet light-emitting diode (UV-LED) irradiation at a wavelength of 365 nm, in the presence of a photoinitiator. Crosslinking occurred smoothly, providing homogeneous hydrogels. The equilibrium swelling ratio, rheology and morphology of these hybrid PNIPAM–PFS-based hydrogels were investigated. The thermo-responsive properties of the hydrogels were studied as a function of the PFS oxidation state. In situ fabrication of silver nanoparticles inside the hydrogel network via reduction of silver nitrate by the PFS chains led to hydrogel composites. These composites showed strong antimicrobial activity while maintaining a high biocompatibility with cells.

The synthesis of a rapidly forming redox responsive poly(ferrocenylsilane)‐poly(ethylene glycol) (PFS‐PEG)‐based hydrogel is described, achieved by a thiol‐Michael addition click reaction. PFS bearing acrylate side groups (PFS‐acryl) was synthesized by side group modification of poly(ferrocenyl(3‐iodopropyl)methylsilane) (PFS‐I) and characterized by ¹H NMR, ¹³C NMR, and FT‐IR spectroscopy. The equilibrium swelling ratio, morphology, rheology, and redox responsive properties of the PFS‐PEG‐based hydrogel are reported. magnified image

This concise paper discusses poly(ferrocenylsilane) (PFS)‐based organometallic gels and hydrogels as a novel class of redox‐responsive materials. First, the use of silicon‐bridged spirocyclic [1]ferrocenophane crosslinkers for creating PFS networks swellable in organic solvents is described. Optical properties of PFS composite colloidal crystal films, composed of monodisperse silica spheres embedded in such PFS networks, are shown to be influenced by solvent swelling or redox chemistry, allowing the use of these composites in photonic crystal full‐color displays. The synthesis of networks composed of water‐soluble PFS polyanions or polycations is discussed. In response to redox stimuli, a polyanionic PFS‐hydrogel exerted a pressure, which could render it useful as an actuator. magnified image

The method of electrophoretic deposition of charged polymer (polystyrene) microspheres on topologically patterned substrates is discussed. Surface patterning with different symmetries and structure periodicity in the sub-micrometer range over large surface areas was realized by laser interference lithography. Growth of colloidal crystals on patterned and bare electrode surfaces was compared. Surface patterning predetermined the colloidal crystal structure and orientation. Fcc colloidal crystals with (111), (100) and (110) crystal plane orientations parallel to the electrode surfaces were successfully grown on patterned electrodes with the corresponding pattern symmetry. The growth of colloidal crystals with (111) and (100) crystal plane orientations parallel to the electrode surface was easily controlled by patterned surfaces, while only two layers of colloidal crystals having the (110) plane orientation parallel to the electrode surface were grown in a controlled way. The growth of thick colloidal crystals in the non-close-packed [110] direction generated a mixture of small domains of different orientations, where domains with (111) and (100) orientations dominated. The thickness of the colloidal crystals was controlled by varying the deposition parameters. Thickness increased with increasing the applied voltage, deposition time, concentration of colloidal particles and with decreasing the withdrawal speed of the electrodes from the colloidal suspension. A threshold voltage of 3.36 V was determined, beyond which a significant increase in the thickness of the colloidal crystals with applied voltage was observed. A gradient in the thickness of the colloidal crystals was obtained across the electrode surface at low withdrawal speed (0.04 mm/s). Colloidal crystals with a homogeneous thickness over the electrode area were formed at withdrawal speeds of 0.07 - 0.1 mm/s.