A versatile preparation of azobenzene-dye functionalized colored polymer nanoparticles by surface modification

A series of stable and translucent colored nanolatex, that is, colloidal aqueous suspensions of dye-tagged polymer nanoparticles (NPs) in the 15- to 20-nm diameter range, have been prepared by covalent attachment of azobenzene chromophores to the surface of reactive NPs. Primary crosslinked NPs bearing chlorobenzyl groups were produced by microemulsion copolymerization of styrene and vinylbenzylchloride. Amine-functionalized NPs were obtained after a second functionalization step with polyamines (cyclam and polypropyleneimine dendrimers of first and third generations). Dye-doped particles were obtained by reacting pyridylazo-dimethylaminobenzene (PADA) with chlorobenzyl-NPs and by reacting amine-reactive dimethylaminoazobenzene dyes (DABsyl, DAB-ITC) as well as Disperse Red I acrylate with polyamine-coated NPs. Regardless the dye solubility, the grafting readily proceeded in aqueous suspensions at room temperature in the presence of a cationic surfactant without added solvent. Purple, red, and orange suspensions (maximum absorption around 550, 500, 430 nm), with dye loads ranging from 0.3 to 1.2 mmol/g, corresponding to 400-1800 azobenzene residues per NP, are obtained. The reported results indicate that functional polymer NPs, with remarkably accessible multiple anchoring sites, are useful building blocks. (C) 2008 Wiley Periodicals, Inc.