Smart polymers: Physical forms and bioengineering applications

Designing surfaces with wettability that varies in response to solute identity and concentration

Surfaces with solute responsive wettability can be prepared by covalent layer-by-layer assembly of PNIPAM-c-PNASI with 10 and 100 nm diameter aminated silica nanoparticles. These surfaces are found to exhibit reversible changes in surface wetting in response to solute anion identity and concentration, allowing surfaces to be switched from hydrophilic (advancing water contact angle 68 degrees ) to hydrophobic (advancing water contact angle 145 degrees ). The extent of the response to solute salts is found to be consistent with the Hofmeister series and with associated changes in surface roughness which result from varying degrees of polymer swelling in response to solute ion identity and concentration. The observed wettability changes on these surfaces are reversible.

Chemical oscillation induced periodic swelling and shrinking of a polymeric multilayer investigated with a quartz crystal microbalance

Poly(acrylic acid- co-3-azidopropyl acrylate) and poly(acrylic acid- co-propargyl acrylate) have been alternately fabricated into a multilayer via the click reaction. The layer-by-layer deposition was monitored with a quartz crystal microbalance with dissipation (QCM-D) in real time. The response of the multilayer under continuous flow of a bromate-sulfite-ferrocyanide solution with pH oscillation has also been investigated by use of QCM-D. As the pH oscillates between 3.1 and 6.6, either the frequency shift (Delta f) or the dissipation shift (Delta D) periodically varies with a constant amplitude, clearly indicating that the multilayer swells and shrinks oscillatedly. The changes of thickness, shear viscosity, and elastic shear modulus further indicate the oscillation.