Observation of nanoparticles and film formation by scanning tunneling microscopy: methyl methacrylate/butyl methacrylate nanoparticles prepared by microemulsion polymerization

Latexes as dispersions of poly(methyl methacrylate-co-butyl methacrylate) copolymeric nanoparticles within water were produced by microemulsion polymerization of the respective comonomers. Polymer yield, number-average and weight-average molecular weights, polydispersity index, and the glass-transition temperature of the copolymer produced were 50%, 8.8 × 104, 2.54 × 105, 2.87, and 45 °C. Scanning tunneling microscopy (STM) images of the latex nanoparticles and film formation on highly oriented pyrolitic graphite (HOPG) were obtained with a 2 V sample bias and a tunneling current of 20 pA. The STM pictures revealed that the particle size was 18 ± 3 nm. There was no film formation in the case of dehydration at room temperature. There was some coalesence of particles when the HOPG surface was preheated at 55 °C, while complete film formation was achieved when the latexes were annealed at 55 °C in an oven for about 10 min.