Synthesis and Characterization of Polypyrrole-Coated Sulfur-Rich Latex Particles:  New Synthetic Mimics for Sulfur-Based Micrometeorites

Polypyrrole (PPy) has been deposited from aqueous solution onto submicrometer-sized sulfur-rich poly[bis(4-vinylthiophenyl)sulfide] (PMPV) latex particles. The PMPV seed particles and resulting composite particles were extensively characterized using scanning electron microscopy, X-ray photoelectron spectroscopy, FT-IR spectroscopy, helium pycnometry, Raman spectroscopy, and electrical conductivity measurements. Four-point probe measurements on pressed pellets indicate conductivities of around 6 × 10-5 S cm-1 for a polypyrrole loading of approximately 11.5%. This suggests a somewhat patchy, nonuniform polypyrrole overlayer, which is consistent with our Raman spectroscopy studies. Despite their relatively low conductivities, these polypyrrole-coated PMPV latexes can be accelerated up to hypervelocities (>20 km s-1) using a high voltage (2 MV) van de Graaf instrument. In view of their high sulfur contents (ca. 28%), these new electrically conductive latexes are expected to be interesting synthetic mimics for understanding the behavior of sulfur-based micrometeorites, whose existence has been postulated by planetary scientists investigating signs of volcanic activity on one of Jupiter's moons (Io).