Photochemical initiated polymerization of single microdroplets

The production of polymeric microspheres via aerocolloidal processing is explored. A droplet consisting of a mixture of 1,6-hexanediol diacrylate and trimethylolpropane ethoxy triacrylate monomers was levitated electrodynamically in the path of an argon ion laser beam (lambda = 488 nm). The laser beam served as the source of illumination for elastic and inelastic light-scattering measurements. The reaction was followed by Raman spectroscopy, and polymerization was initiated with an alpha alpha-amino acetophenone derivative which undergoes alpha-cleavage upon exposure to the laser light. The diameters of the suspended droplets were typically 20-80 mu m, producing polymeric microspheres of approximately the same size. The size and refractive index of the product microspheres were determined by elastic light-scattering. The Raman data show the elimination of carbon-carbon double bonds and the formation of C-H bonds as rapid polymerization proceeded.