Reversible Swelling of Chitosan and Quaternary Ammonium Modified Chitosan Brush Layers: Effect of pH and Counter Anion Size and Functionality.

This study investigates the swelling of grafted polycationic brushes as a function of pH and anion type. The brushes are chitosan (CH) and chitosans with 27% and 51% degree of substitution (DS) of quaternary ammonium salt, denoted as CH-Q(25) and CH-Q(50), respectively. The water content and swelling behaviors are monitored using in situ quartz-crystal microbalance with dissipation (QCM-D).

Photocatalytic and conductive MWCNT/TiO2 nanocomposite thin films.

A conductive and photocatalytic nanocomposite thin film comprising multiwalled carbon nanotubes (MWCNTs) and TiO2 nanoparticles is fabricated based on layer-by-layer (LbL) assembly in a nonpolar solvent, toluene. An amphiphilic surfactant, aerosol OT (AOT), is used to impart opposite surface charge onto MWCNTs and TiO2 in toluene. Our fabrication technique enables the incorporation of unoxidized MWCNTs into the nanocomposite thin films, and at the same time, provides a versatile method of fabricating conformal thin films over a large area.

Layer-by-layer assembly of charged particles in nonpolar media.

Layer-by-layer (LbL) assembly of charged species such as nanoparticles and polymers has been widely used to generate functional thin films with unique wetting, optical, catalytic, and biological properties. Although LbL assembly is a versatile tool for creating functional thin films on a variety of substrates, it is generally restricted to aqueous media, in which electrolytes ionize readily due to the large dielectric constant of water. LbL assembly of non-water-soluble materials would expand the range of film properties and functionalities that are attainable.