Visible light induced RAFT for asymmetric functionalization of silica mesopores

One key feature for bioinspired transport design through nanoscale pores is nanolocal, asymmetric as well as multifunctional nanopore functionalization. Here, we use a visible-light induced, controlled photo electron/energy transfer-reversible addition–fragmentation chain-transfer (PET-RAFT) polymerization for asymmetric polymer placement into mesoporous silica thin films including asymmetric polymer sequence design

Proton and Calcium-Gated Ionic Mesochannels: Phosphate-Bearing Polymer Brushes Hosted in Mesoporous Thin Films As Biomimetic Interfacial Architectures

Rational construction of interfaces based on multicomponent responsive systems in which molecular transport is mediated by structures of nanoscale dimensions has become a very fertile research area in biomimetic supramolecular chemistry. Herein, we describe the creation of hybrid mesostructured interfaces with reversible gate-like transport properties that can be controlled by chemical inputs, such as protons or calcium ions. This was accomplished by taking advantage of the surface-initiated polymerization of 2-(methacryloyloxy)ethyl phosphate (MEP) monomer units into and onto mesoporous silica thin films. In this way, phosphate-bearing polymer brushes were used as “gatekeepers” located not only on the outer surface of mesoporous thin films but also in the inner environment of the porous scaffold. Pore-confined PMEP brushes respond to the external triggering chemical signals not only by altering their physicochemical properties but also by switching the transport properties of the mesoporous film. The ion-gate response/operation was based on the protonation and/or chelation of phosphate monomer units in which the polymer brush works as an off-on switch in response to the presence of protons or Ca2+ ions. The hybrid meso-architectured interface and their functional features were studied by a combination of experimental techniques including ellipso-porosimetry, cyclic voltammetry, X-ray reflectivity, grazing incidence small-angle X-ray scattering, X-ray photoelectron spectroscopy, and in situ atomic force microscopy. In this context, we believe that the integration of stimuli-responsive polymer brushes into nanoscopic supramolecular architectures would provide new routes toward multifunctional biomimetic nanosystems displaying transport properties similar to those encountered in biological ligand-gated ion channels.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasConsejo Nacional de Investigaciones Científicas y Técnica

Heterogeneous Catalytic Activity of Platinum Nanoparticles Hosted in Mesoporous Silica Thin Films Modified with Polyelectrolyte Brushes

Platinum nanoparticles of 3 nm diameter were included in mesoporous silica thin films by controlling the mesopore surface charge with a short polymer brush. This metal-polymer-mesopore nanocomposite presents high catalytic activity toward ammonia oxidation at low temperatures with 4.5% weight platinum loading. An anomalous partial selectivity toward nitrous oxide is observed for the first time, which can be traced back to the synergy of the particles and modified surface. This effect opens a path toward the design of nanocomposite catalysts with highly controlled environments, in which the size- and function-controlled cavities can be tuned in order to lower the reaction barriers.Fil: Rafti, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Brunsen, Annette. Universitat Technische Darmstadt; Alemania. Comisión Nacional de Energía Atómica. Gerencia del área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); ArgentinaFil: Fuertes, Maria Cecilia. Comisión Nacional de Energía Atómica. Gerencia del área de Seguridad Nuclear y Ambiente. Gerencia de Química (cac); Argentina. Universidad Nacional de San Martin. Instituto Sabato; ArgentinaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica. Gerencia del área de Seguridad Nuclear y Ambiente. Gerencia de Química (cac); Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Quimica Fisica; Argentin

Ferrocene Polymers for Switchable Surface Wettability

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 degrees after oxidation could be observed, while the effect for immobilized PVFc after oxidation was less pronounced (CA drop of approximately 30 degrees). 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

Defined core–shell particles as the key to complex interfacial self-assembly

The two-dimensional self-assembly of colloidal particles serves as a model system for fundamental studies of structure formation and as a powerful tool to fabricate functional materials and surfaces. However, the prevalence of hexagonal symmetries in such self-assembling systems limits its structural versatility. More than two decades ago, Jagla demonstrated that core–shell particles with two interaction length scales can form complex, nonhexagonal minimum energy configurations. Based on such Jagla potentials, a wide variety of phases including cluster lattices, chains, and quasicrystals have been theoretically discovered. Despite the elegance of this approach, its experimental realization has remained largely elusive. Here, we capitalize on the distinct interfacial morphology of soft particles to design two-dimensional assemblies with structural complexity. We find that core–shell particles consisting of a silica core surface functionalized with a noncrosslinked polymer shell efficiently spread at a liquid interface to form a two-dimensional polymer corona surrounding the core. We controllably grow such shells by iniferter-type controlled radical polymerization. Upon interfacial compression, the resulting core–shell particles arrange in well-defined dimer, trimer, and tetramer lattices before transitioning into complex chain and cluster phases. The experimental phase behavior is accurately reproduced by Monte Carlo simulations and minimum energy calculations, suggesting that the interfacial assembly interacts via a pairwise-additive Jagla-type potential. By comparing theory, simulation, and experiment, we narrow the Jagla g-parameter of the system to between 0.9 and 2. The possibility to control the interaction potential via the interfacial morphology provides a framework to realize structural features with unprecedented complexity from a simple, one-component system