Preparation of fluorescent particles dispersible in organic solvents

COLL 516

Hua Hu, Chemical Engineering, University of Michigan, 2300 Hayward St., Ann Arbor, MI 48109 and Ronald Larson, Dept. of Chemical Engineering, University of Michigan, 2300 Hayward, Ann Arbor, MI 48109-2136.
We introduce a fast and simple one-step method to synthesize monodisperse fluorescent particles that can be dispersed in organic solvents and have long excitation (644nm) and emission wavelengths (665nm). A lipophilic fluorescent dye, 1,1'-dioctadecyl-3,3,3',3'- tetramethylindodicarbocyanine perchlorate (DiIC18(5)), is directly incorporated into PMMA particles through dispersion polymerization. A poly hydroxystearic acid graft (poly) methyl methacrylate (MM) and methacrylic acid (MA) copolymer is used as a stabilizer to prevent the particles from aggregating and flocculating in the non-aqueous solvents. Experimental results show that the fluorescent PMMA particles are very uniform in size, bleach at very low rate and behave like hard spheres. One important achievement in our synthesis protocol is that we are able to produce particles of a desired size by choosing the composition of the reactants according to a pre-determined relationship between particle size and composition of reactants. In addition, the effects of fluorescent dye and polar solvent (ethanol) on the formation and size of particles are discussed.