-
[show abstract]
[hide abstract]
ABSTRACT: The design of hybrid mesoporous materials incorporating polymeric assemblies as versatile functional units has become a very fertile research area offering major opportunities for controlling molecular transport through interfaces. However, the creation of such functional materials depends critically on our ability to assemble polymeric units in a predictable manner within mesopores with dimensions comparable to the size of the macromolecular blocks themselves. In this work, we describe for the first time the manipulation of the molecular transport properties of mesoporous silica thin films by the direct infiltration of polyelectrolytes into the inner environment of the 3D porous framework. The hybrid architectures were built up through the infiltration-electrostatic assembly of polyallylamine (PAH) on the mesopore silica walls, and the resulting systems were studied by a combination of experimental techniques including ellipso-porosimetry, cyclic voltammetry and X-ray photoelectron spectroscopy, among others. Our results show that the infiltration-assembly of PAH alters the intrinsic cation-permselective properties of mesoporous silica films, rendering them ion-permeable mesochannels and enabling the unrestricted diffusion of cationic and anionic species through the hybrid interfacial architecture. Contrary to what happens during the electrostatic assembly of PAH on planar silica films (quantitative charge reversal), the surface charge of the mesoporous walls is completely neutralized upon assembling the cationic PAH layer (i.e., no charge reversal occurs). We consider this work to have profound implications not only on the molecular design of multifunctional mesoporous thin films but also on understanding the predominant role of nanoconfinement effects in dictating the functional properties of polymer-inorganic hybrid nanomaterials.
Langmuir 03/2011; 27(8):4328-33. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A robust and straightforward strategy allowing the controlled confinement of metal nanoparticles within the 3D framework of mesoporous films is presented. The chemical methodology is based on the inner surface modification of mesoporous silica films with polyelectrolyte brushes. We demonstrate that the macromolecular building blocks significantly enhance the site-selective preconcentration of nanoparticle precursors in the inner environment of the mesoporous film. Then, chemical reduction of the preconcentrated precursors led to the formation of metal nanoparticles locally addressed in the mesoporous structure. We show that the synergy taking place between two versatile functional nanobuilding blocks (ordered mesocavities and polymer brushes) can produce stable embedded nanoparticles with tuned optical properties in a very simple manner. As a general framework, the strategy can be easily adapted to different sets of polymer brushes and mesoporous films in order to regulate the monomer-precursor interactions and, consequently, manipulate the site-selective character of the different chemistries taking place in the film. We consider that the "integrative chemistry" approach described in this work provides new pathways to manipulate the physicochemical characteristics of hybrid organic-inorganic advanced functional assemblies based on the rational design of chemistry and topology in confined environments.
Langmuir 02/2010; 26(8):5559-67. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Rational design of fully synthetic platforms displaying active control over ionic transport in close resemblance to biological systems represents an ongoing challenge in molecular materials science. Here, we demonstrate that the synergism arising from the chemistries involved in mesoporous films and polymer brushes is a key enabler to next-generation "smart" nanofilters capable of mimicking the gating functions of specific biological channels. Hybrid functional assemblies constituted of mesoporous silica films modified with polyzwitterionic brushes are able to discriminate and gate the transport of cations while the passage of anionic species is precluded. The synthetic membranes behave as proton-gated cation-selective platforms mimicking the functioning of acid-sensing ion channels encountered in the neurons of the central nervous system. We believe that this experimental evidence will stimulate further multidisciplinary work across the boundaries of materials chemistry to attain new functional nanostructured interfaces with transport properties so far believed to be exclusive features of biological channels.
Journal of the American Chemical Society 09/2009; 131(31):10866-8. · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We showed for the first time how to tailor the permselectivity of mesoporous thin films by changing the electrostatic environment of the nanopores through the covalent functionalization with polyelectrolyte brushes.
Chemical Communications 06/2009; · 6.17 Impact Factor
