© Copyright 1997 American Chemical Society
APRIL 30, 1997 VOLUME 13, NUMBER 9
Letters A Dispersion Polymerization System with Nuclei Distinguishable from Polymer Particles Tarun K. Mandal and Broja M. Mandal* Polymer Science Unit, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India Received June 21, 1996. In Final Form: January 30, 1997X A dispersion polymerization is described wherein the nuclei are distinguished from polymer particles. Specifically, it has been observed that dispersion polymerization of pyrrole using FeCl3 oxidant in pure or 70% ethanol yields dispersions with two kinds of particles: (i) nanoparticles of 50 nm.9 By use of homopolymers as stabilizers the first observable particles were found to be in the 100-500 nm size range.13 This size is rather large and has been attributed to the fact that the in-situ grafted stabilizer rather than the homopolymer stabilizer acts as the real stabilizer. The graft concentration is zero at the start, and before enough graft becomes available for stabilization of the particles, coalescence advanced to the above level. Thus, in a dispersion polymerization system one is expected to observe only the particles when the nuclei are unstable. On the other hand, another situation may arise if the nuclei are metastable, i.e., they are isolable and yet they are unstable toward capture by the particles (heterocoalescence). We describe here a system wherein such a situation is encountered. In an earlier publication we reported that the as-prepared polypyrrole dispersions prepared with FeCl3 initiator in aqueous ethanol media contain both nanoparticles (
