Mesoporous thin films meet macromolecular brush polymers: Tuning the surface and volume chemistry of nanocavity arrays with tailored perm-selective or optical properties

A. CALVO; B. YAMEEN; M. C. FUERTES; F. J. WILLIAMS; O. AZZARONI; G. J. A. A. SOLER-ILLIA

Congreso; PACIFICHEM 2010; 2010

Rational design of “smart materials” able to react to the environment represents an ongoing challenge in molecular materials science. The chemical processes that occur in membranes, micelles or nanopores are fundamental for many synthetic procedures used in nanoscience and nanotechnology. In such physically constrained environments, interfacial interactions, symmetry breaking, and confinement-induced entropy loss can play dominant roles in determining molecular organization or chemical reactivity. In some cases it has been suggested that nanoscale confinement could be harnessed as a “synthetic tool” to modify materials’ properties. Mesoporous materials with monodisperse, ordered pores in the 2-50 nm range, constitute a robust functional scaffold with tailored cavity size, shape, interconnectivity and surface properties. Functional polyelectrolyte brushes are versatile polymers that can be nanoscale designed to respond to external solicitations such as pH, temperature, etc. The combination of these two building blocks can lead to a “nanotoolbox” of spatially located functions with well-defined chemical functionality. In this work, we present the chemical strategies to produce functional polyelectrolyte brushes within the 3D framework of mesoporous hybrid thin films. An initiator group is attached to dangling amino organic groups; subsequent polymerization leads to smooth inclusion of anionic, cationic or zwitterionic brushes within the pores. The macromolecules significantly modify the properties of the pore system. Perm-selectivity towards electrochemical probes can be switched by modifying the mesopore surface functions with the polyelectrolyte. When a zwitterion is grafted, ion gating is achieved. Cationic polyelectrolytes permit to locally produce gold nanoparticles in the mesopores by pre-concentrating the metal precursor. The integration of mesoporous films and polymer brushes provides a core concept to design complex architectures with synergic properties.