Asymmetric Faradaic system based on organometallic electrodes shows suppression of parasitic water reactions and remarkable selectivity in redox-mediated electrosorption of micropollutants.

The living anionic copolymerization of isoprene and styrene in cyclohexane affords tapered block copolymers due to the highly disparate reactivity ratios of r I = 12.8 and r S = 0.051. Repeated addition of a mixture of these monomers was exploited to generate tapered multiblock copolymer architectures of the (AB) n type with up to 10 blocks (1 ≤ n ≤ 5), thereby subdividing the polymer chains in alternating flexible polyisoprene (PI) and rigid polystyrene (PS) segments. Three series of well-defined tapered multiblock copolymers with approximate molecular weights of 80, 240, and 400 kg/mol were prepared on the 100 g scale. Via this synthetic strategy polymer chains were divided in di-, tetra-, hexa-, octa-, and decablock tapered multiblock structures. Because of the living nature of the polymerization, low dispersities in the range 1.06–1.28 (decablock) were obtained. To ensure full monomer conversion prior to the addition of the isoprene/styrene mixture, kinetic Monte Carlo simulation was employed, permitting to simulate chain growth in silico by employing the known polymerization rates and rate constants k p. The synthesized tapered multiblock copolymers were characterized via SEC and selected samples via oxidative degradation of the polyisoprene block in solution, confirming the well-defined nature of the PS segments. Subsequently, the question was addressed, to which extent the tapered multiblock copolymers are capable of forming ordered nanosegregated morphologies. Detailed thermal, structural, and rheological investigations showed that the tapered multiblock copolymers with a molecular weight of 240 kg/mol formed ordered phases with the expected lamellar morphology. However, X-ray scattering data and transmission electron microscopy (TEM) images of the octablock and decablock copolymers reflect weakly ordered structures at ambient temperature. The domain spacing, d, was found to scale as d ∼ N 0.62, where N is the total degree of polymerization, suggesting stretching of chains and nonideal configurations. Following the structure factor, S(q), as a function of temperature revealed that the tapered multiblock copolymers undergo a fluctuation-induced first-order transition at the respective order-to-disorder transition temperature, T ODT. The viscoelastic response of the tapered copolymers was controlled by the nanodomain structure, the degree of segregation, nanodomain-bridging configurations of blocks, and also the proximity to the glass temperature of the vitrified PS domains. Tapered hexablock copolymers were found to best combine structural integrity and mechanical toughness, while maintaining a large strain at break (>900%).

The changes in surface wettability induced by immobilized polyvinylferrocene (PVFc) and poly(2-(methacryloyloxy)ethyl ferrocenecarboxylate) (PFcMA) on silica wafers were studied after oxidation with two different oxidation reagents. Surface-attached PFcMA was accessible by applying a surface-initiated atom transfer radical polymerization (SI-ATRP) protocol, while end-functionalized PVFc was immobilized by using a grafting onto approach. In the case of PFcMA, a remarkable contact angle (CA) drop for water of approximately 70°after oxidation could be observed, while the effect for immobilized PVFc after oxidation was less pronounced (CA drop of approximately 30°). In the case of PFcMA, the effect of chain length was additionally studied, showing a more significant CA drop for PFcMA chains with higher molar masses.

Controlling structure and function to switch ionic transport through synthetic membranes is a major challenge in the fabrication of functional nanodevices. Here we describe the combination of mesoporous silica thin fi lms as structural unit, functionalized with two different redox-responsive ferrocene-containing polymers, polyvinylferrocene (PVFc) and poly(2-(methacryloyloxy)ethyl ferrocenecarboxylate) (PFcMA), by using either a grafting to, or a grafting from approach. Both mesoporous fi lm functionalization strategies are investigated in terms of polymer effect on ionic permselectivity. A signifi cantly different ionic permselective behavior can be observed. This is attributed to different polymer location within the mesoporous fi lm, depending on the functionalization strategies used. Additionally, the infl uence of chemical oxidation on the ionic permselective behavior is studied by cyclic voltammetry showing a redox-controlled membrane gating as function of polymer location and the pH value. This study is a fi rst step of combining redox-responsive ferrocene-containing polymers and mesoporous membranes, and thus towards redox-controlled ionic transport through nanopores.

The response of switchable polymer blends and coatings to temperature variation is important for the development of high-performance materials. Although this has been well studied for bulk materials, a proper understanding at the molecular level, in particular for high stretching forces, is still lacking. Here we investigate the molecular details of the temperature-dependent elastic response of two widely used water-soluble polymers, namely, polyethylene glycol (PEG) and poly­(N-isopropylacrylamide) (PNiPAM) with a combined approach using atomic force microscopy (AFM) based single molecule force spectroscopy (SMFS) experiments and molecular dynamics (MD) simulations. SMFS became possible by the covalent attachment of long and defined single polymers featuring a functional end group. Most interestingly, varying the temperature produces contrasting effects for PEG and PNiPAM. Surprising as these results might occur at first sight, they can be understood with the help of MD simulations in explicit water. We find that hydration is widely underestimated for the mechanics of macromolecules and that a polymer chain has competing energetic and entropic elastic components. We propose to use the temperature dependence to quantify the energetic behavior for high stretching forces. This fundamental understanding of temperature-dependent single polymer stretching response might lead to innovations like fast switchable polymer blends and coatings with polymer chains that act antagonistically.