Single-molecule particles of a series of water-soluble polymers are prepared via a spray dryer from dilute polymer aqueous solutions. Two of these polymers, poly(acrylic acid) and polyacrylamide, are used as examples to illustrate the preparation and identification of single-chain molecules. Scanning electron microscopy shows that these dried particles possess diameters ranging from 1 to 4 mum. Transmission electron microscopy reveals that each particle consists of numerous distinctly separated small particles with a radius of a few nanometers. Each of these particles consists of a single-chain molecule, a conclusion based on calculations of volume involving the polymer molecular weight. This method lends itself to the preparation of single-molecule particles of water-soluble polymers in mass quantity, which may provide a gateway to studying the chemistry and physics of polymer single-molecules in a condensed state. (C) 2001 Elsevier Science Ltd. All rights reserved.