Facile control of thermo-responsive wettability through an all-electrostatic self-assembling process

We describe the facile fabrication of a thermo-responsive wetting surface through an electrostatic assembly process and the use of thermo-responsive polyelectrolyte copolymers. The organic-inorganic nano-structured films were prepared through the layer-by-layer assembly of negatively charged silica nanoparticles (11 nm) and positively charged poly(allylamine hydrochloride) (PAH). The thermo-responsive polyelectrolyte copolymer, poly(allylamine hydrochloride)-g-poly(N-isopropylacrylamide) (PAH-g-PNIPAAm), was synthesized by grafting a carboxylic end group of PNIPAAm on to the PAH. The nanostructured surfaces modified with PAH-g-PNIPAAm exhibit enhanced thermal switching of surface wettability. Our approach provides a versatile strategy for control over the thermo-responsive wettability of substrates with complex structures for various applications such as sensors, microfluidics, etc. (C) 2008 Elsevier B.V. All rights reserved.