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) c opolymeric nanoparticles within water were produced by microemulsion polyme rization of the respective comonomers. Polymer yield, number-average and we ieht-average molecular weights, polydispersity index, and the glass-transit ion temperature of the copolymer produced were 50%, 8.8 x 10(4), 2.54 x 10( 5), 2.8'7, and 45 degrees C. Scanning tunneling microscopy (STM) images of the latex nanoparticles and film formation on highly oriented pyrolitic gra phite (HOPG) were obtained with a 2 V sample bias and a tunneling current o f 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 degrees C, while complete film formation was achieved when the latex es were annealed at 55 degrees C in an oven for about 10 min.