Photoreactive Azido-Containing Silica Nanoparticle/Polycation Multilayers: Durable Superhydrophobic Coating on Cotton Fabrics

摘要

In this study, we report the functionalization ofnsilica nanoparticles with highly photoreactive phenyl azidongroups and their utility as a negatively charged building blocknfor layer-by-layer (LbL) electrostatic assembly to produce anstable silica nanoparticle coating. Azido-terminated silicannanoparticles were prepared by the functionalization of barensilica nanoparticles with 3-aminopropyltrimethoxysilane followednby the reaction with 4-azidobenzoic acid. The azidonfunctionalization was confirmed by FTIR and XPS. Poly-n(allylamine hydrochloride) was also grafted with phenyl azidongroups and used as photoreactive polycations for LbLnassembly. For the photoreactive silica nanoparticle/polycation multilayers, UV irradiation can induce the covalent cross-linkingnwithin the multilayers as well as the anchoring of the multilayer film onto the organic substrate, through azido photochemicalnreactions including C−H insertion/abstraction reactions with surrounding molecules and dimerization of azido groups. Ournresults show that the stability of the silica nanoparticle/polycation multilayer film was greatly improved after UV irradiation.nCombined with a fluoroalkylsilane post-treatment, the photoreactive LbL multilayers were used as a coating fornsuperhydrophobic modification of cotton fabrics. Herein the LbL assembly method enables us to tailor the number of thencoated silica nanoparticles through the assembly cycles. The superhydrophobicity of cotton fabrics was durable against acids,nbases, and organic solvents, as well as repeated machine wash. Because of the unique azido photochemistry, the approach usednhere to anchor silica nanoparticles is applicable to almost any organic substrate.