Well-defined poly(2-(methacryloyloxy)ethyl ferrocenecarboxylate) (PFcMA) brushes were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) on cross-linked polystyrene particles. The ATRP of FcMA monomer was reinvestigated leading to molar masses up to 130 kg mol–1 with a good reaction control and high monomer conversion (91%). The SI-ATRP was done with different amounts of initiator in the PS particle shell leading to PFcMA surface conformations from “mushroom-like” to dense “brush-like” polymers, which could be confirmed by dynamic light scattering (DLS) experiments. Redox-responsive behavior of the PFcMA shell was investigated by DLS and cyclic voltammetry (CV) measurements indicating a tremendous increase in the hydrodynamic volume of the ferrocene-containing shell. The transformation of PFcMA-grafted PS particles to magnetic iron oxides after thermal treatment could be investigated by SQUID magnetization measurements showing the typical hysteresis for ferromagnetic material.

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.

Polymer modification of mesoporous materials is a relevant topic for applications from sensing and separation to drug delivery. Especially the combination of structure and responsive, charged polymer functionalization opens new possibilities, such as gating of drug release. Thereby, zwitterionic polymers are interesting, because of their antifouling characteristics and their influence on ionic permselectivity. The control on polymerization in confinement of a mesopore including spatial polymer location is crucial for the resulting mesopore function such as ionic permselectivity. The amount of generated polymer and polymerization kinetics should be influenced by the confinement of mesopores: Diffusion is limited by the pore size, pore connectivity, and wall charge. These parameters influence termination, which depends on radical concentration and proximity. Concerning the total surface area, the size of the internal surface area of mesoporous materials largely dominates over the size of the outer surface area. This might tempt one to relate observed functionalization effects to the internal surface. Here, we investigate iniferter-initiated polymerization in thin mesoporous silica films concerning the type of iniferter, the generated amount of polymer, the polymerization inside the mesopores versus the external surface, and the used monomer. Our results clearly indicate potential bottlenecks of iniferter-initiated polymerizations in mesopores. The charge of the monomer can be crucial for the generated amount of polymer inside the mesopores and the exterior surface can dominate the polymerization. These results emphasize that polymer distribution in mesoporous materials must be analyzed carefully before data interpretation and that polymerization inside nanometer-sized pores can be controlled by confinement effects. We expect these results to have great impact, e.g., on the design of miniaturized separation and sensing devices, and to open new confinement-controlled functionalization strategies.

Microphase separation drives the structure formation in block copolymers. Here, functional metallopolymer-grafted diblock copolymers consisting of polystyrene-block-polyisoprene (PS-b-PI) as polymer backbone featuring low molar mass poly­ferrocenyl­dimethyl­silane (PFS) and polyvinyl­ferrocene (PVFc) are synthesized via an iterative anionic grafting-to polymerization strategy. PS-b-PI block copolymers having about 30 mol % 1,2-polyisoprene moieties are subjected to platinum-catalyzed hydrosilylation reaction for the introduction of chlorosilane groups. The Si–Cl moieties are shown to efficiently react with the active metallopolymers yielding block-selective metallopolymer-grafted copolymers with 34 vol % PVFc and 43 vol % PFS as evidenced by 1H NMR spectroscopy as well as size exclusion chromatography. The microphase separation of the functional metallopolymer-grafted block copolymers is evidenced via TEM measurements revealing fascinating morphologies. The structure formation of the PVFc-grafted block copolymers is studied in more detail by TEM, small-angle X-ray scattering, wide-angle X-ray scattering, and atomic force microscopy measurements evidencing a lamellar morphology featuring a spherical substructure for the PVFc segments inside the polyisoprene lamellae.